Well, the parts are in Thumbdoctors hands now and the task of blueprinting is at hand. We're all going to watch as he works his way through it and works his magic.

Feel free to help us out with your suggestions.

I'm going to post the before pix. This first one is of the exhaust ports form the top. The build-up around the port is not carbon. It's grease left over from CC'ing the case. Which works out to a 1.493:1 by the way for a primary CR.

Here are the intake ports from the top.

Here's a pic of the intake tract.

Here's a pretty good pic of port relationship from the top.

Intake ports and tunnels from the bottom.

Better shot of intakes.

Scavenge/transfers.

View of the exhaust port from the bottom.

Well, It's pretty hard for a lot of you folks to imagine snowmobile engine porting when it's 90 degrees and 80% humidity outside so I don't blame anyone for not following this thread til October. As promised, I'll start in this mill's basement and work towards the back door. After unpacking Idooski's marvelously wrapped pieces, I started to inspect them starting at the reed cages. The first thing I noticed, is a common issue with all Rotax case / reed engines, the reed stoppers touch the inside walls of the reed box. This in my humble opinion poses a reliability problem. First off, the hardened steel stoppers are vibrating against the walls at such a degree to feed the motor with a good supply of both aluminum & steel particles and fatigue the Petal retaining screws. There's no room for a wayward screw head to find it's way downstream, but the loss of reed petal clamping force will add to the already critical mid-range lean condition through unwanted case pressure reversion. As any vibration expert (Dynamo^joe comes to mind) will tell you, vibration at certain amplitudes can be very destructive. So keep this clearance in mind when adding thicker or multiple reed set ups on your own rigs. See arrows on attached image :nervous:

The reed box damage :nervous: Caught before real damage occurs

The next problem is with the reed cage, a couple of petals aren't seating causing delayed crankcase pressurization (up to 20 degrees crankshaft rotation to close those suckers !). There should be an airtight seal between petals & cage without too much tension on the petals. This balancing act seporates the good, the bad and the ugly in after-maket reeds. Too loose - lost intake timing building back-pressure to close them, too stiff loss of intake timing to create enough vacuum to open them. The best way to diagnose bad reed sealing is with a 0 -15 inches of mercury vacuum gage hooked up to the boost bottle(removed & blocked) port with the engine idling at 2000 rpm, the gage needle should be reasonably stable, if it quivers 6 inches of mercury or more bingo there's one problem solved !. The attached image is of a reed cage held up to a spot light, see if you can spot the bad petals. :sly:

OK, Lets get down to work, attached (Uppercase.jpg) is an image of the upper crankcase, you may notice the stamp "J0" in bridge between the cylinder base decks the J is for January and the "0" is for '00 (2000). The older motors were julian dated Eg. #59 would mean the 59th day of '03 or Feb 28, 2003. This is important as earlier blocks (the 700cc's come to mind) have oil galleries drilled into the transfer port bowls in the upper cases to lube the mag / PTO bearings and the cast in rails should be left intact because injection oil lubes them. Newer assemblies are un-drilled (magrail.jpg, ptorail.jpg, magGallery.jpg, ptogallery.jpg) use isoflex p/n 293550021 bearing lube and do not need the rails to guide the oil flow. One foot note: When the case halfs are split on blocks that use Isoflex lube be sure to reseal with P/N 420297905 silicone sealant as the old style gasket eliminator (bombi P/N 413702700 loctite 515) reacts chemically with the bearing lube (bad thing!). That rail is going to be removed and the case & jugs will be matched. See Arrows. :nervous:

Attached: un-drilled oil gallerys (Mag)

Attached: un-drilled oil gallerys (PTO). Notice the etching on the bearing saddle, that's the reaction between anti-seize & Isoflex bearing lube (unsociable stuff !)

Attached: images of the cast in oil rails to be removed (Magrail & PTOrail.jpg) Then alignment piloting and case to jug matching will follow, stay tuned!!!

Attached: PTO side

Another thing came to mind when I was inspecting the Series 3 RAVE passages. The port side of the guillotine passage should be left with a sharp edge to scrap carbon build up off. If that area is chamfered or rounded over it allows carbon residue to migrate up into the thrust bearing surface and eventually wedge the valve closed. I learned this fact from automatic transmission valve bodies & hydraulic sleeve valves have sharp edges left purposely to stop debris from wedging valves open / closed. See Attached Image: Exhaustport.jpg :(

I think you guys are doing a great job here with this step by step process. Very interesting. To hell with the 90 deg. weather! This is the best project for this time of the year.

Looking foward to the next steps.

thanks

Looks good, man!!! :thumbsup: The pictures are coming out great, too.

I have an '03 Doo mod motor here that has the oil passages drilled. Do you think it is just for that motor, or are they going back to the drilled passages?

Before we get to the cutting and grinding< I thought I&#39;d share a few pointers on working with Nicasil plated cylinders. First, the plating is very hard but also very brittle. Don&#39;t attack the port windows with an aluminum cutter. The pattern on these files create enough vibration to chip large chunks out of the plating negating another trip to the re-plater and copious amounts of $$$. Start at the port windows with a fine abrasive stone which has been soaked in oil (2 stroke synthetic works). Work around your port entrances to match the scribed lines (machinists dye). The most critical part is to get the windows straight & square, then work into the port blending the new shape. Do the work in shifts, make patterns to assure consistency in curvature of the blends. Smooth out bumps & casting flash. Don&#39;t take a "more is better" approach here or you&#39;ll be visiting your dealers parts dept after many hours trying to tune that hogged out dog!. Attached is the base layout I did of the port alignment and configuration. The way to perform this exercise is well documented here (http://macdizzy.com/cylinder_map.htm). Make a port map and measure the port area by transferring the port sizes and layout on to graph paper (It&#39;s all on the MacDizzy site). I used a SAE two stroke engine designing program to estimate the port sizes. A better bet would be to take a Rotax design engineer out for a few drinks then squeeze the blue print info out of him. Most 2 stroke design software will only make predictions based on "perfect World scenarios".

Originally posted by idooski@Aug 5 2003, 08:48 PM
Looks good, man!!! :thumbsup: The pictures are coming out great, too.

I have an &#39;03 Doo mod motor here that has the oil passages drilled. Do you think it is just for that motor, or are they going back to the drilled passages?
Idooski, can you find a date stamp on that &#39;03 mill. It seems like an odd ball or Bombardier has finally blinked at main bearing poker :D

Originally posted by Thumbdoctor+Aug 6 2003, 12:57 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Thumbdoctor @ Aug 6 2003, 12:57 AM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-idooski@Aug 5 2003, 08:48 PM
Looks good, man!!! :thumbsup:* The pictures are coming out great, too.

I have an &#39;03 Doo mod motor here that has the oil passages drilled. Do you think it is just for that motor, or are they going back to the drilled passages?
Idooski, can you find a date stamp on that &#39;03 mill. It seems like an odd ball or Bombardier has finally blinked at main bearing poker :D [/b][/quote]
It has G2 stamped on it. July &#39;02?

There is also an &#39;02 casting signature on it. I was told by the racer that it was an &#39;03 mill. He ran it Snow-X last year.

Originally posted by idooski+Aug 6 2003, 07:08 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (idooski @ Aug 6 2003, 07:08 AM)</td></tr><tr><td id='QUOTE'> Originally posted by Thumbdoctor@Aug 6 2003, 12:57 AM
<!--QuoteBegin-idooski@Aug 5 2003, 08:48 PM
Looks good, man!!! :thumbsup:* The pictures are coming out great, too.

I have an &#39;03 Doo mod motor here that has the oil passages drilled. Do you think it is just for that motor, or are they going back to the drilled passages?
Idooski, can you find a date stamp on that &#39;03 mill. It seems like an odd ball or Bombardier has finally blinked at main bearing poker :D
It has G2 stamped on it. July &#39;02?

There is also an &#39;02 casting signature on it. I was told by the racer that it was an &#39;03 mill. He ran it Snow-X last year. [/b][/quote]
Yep July 02 is an 03. I was told that the racing setups were running pre-mix so the galleries were drilled. Another rumour I learned from the ultra-lite guys is that Rotax will be starting to us "Lost Foam" foundry processes in up-coming castings. Lost foam is a process of making intricate cores(positives) out of a gas free styro-foam which is used to hold molding sections (ports, water jackets) in shape until the molten aluminum sets up, then the foam vaporizes leaving almost flawless finish on the cavities it once occupied. Mercury Marine developed this process and was contracted by GM to cast the LT5 5.7liter Twin Cam "King of the Hill" vette motors with it.

I can honestly say that I&#39;m pretty impressed by this project and especially by the fact that you are explaining the do&#39;s and don&#39;ts to us. The pictures are great. Keep up the great job. I&#39;ll be checking the progress often.[quote]The older I get, the faster I was!

Well sorry for the delay folks, I couldn&#39;t get the TSR blue-print output into a small enough format to attach so I got out my drawing table and penned it. On the attached I rounded off the basic port dimensions into millimeters. I had to take this rounding off route because the original port window chamfers were a disaster. I took measurements of the largest openings then transferred them to this blueprint to get an average. Your port layouts may differ plus or minus a millimeter. The important thing is not to enlarge the ports beyond the limit done by the manufacturer&#39;s average. The object of this exercise is to straighten out the port windows first, then blend the port bowls to match, respecting the angles of trajectory the designers intended. Example: if the entrance into the cylinder is swept at 60 degrees, maintain that angle when blending. The entrance angles are there to create good scavenging (evacuate spent gases from the combustion chamber) after the boost port then side transfers are uncovered by the piston on it&#39;s downward stroke. This pushes the gases towards the exhast port where the pipe&#39;s (expansion chamber&#39;s) pressure pulse should pull spent exhast gases out thus reducing intake charge contamination.

:p So much for cylinder layout. Now let&#39;s head downstairs to see what can be done to improve the match between the upper half of the crankcase and the intake tracts of the jugs. There&#39;s a lot of bumps & steps in the transfer from the reed box to the upper case transfer bowls. :cussing: The fresh inlet mixture doesn&#39;t really mind a rough or satin finish on the port walls but throw a few lumps, bumps and curves and you&#39;ll lose mixture velocity. We want the Fuel / Air to tumble to help maintain even mixture strength but we don&#39;t want slow it down too much. attached are images of the basic procedure for inking (Machinist&#39;s Dye) the components that will need to be matched (blending of components without a dramatically increasing crankcase volume. &#33;!! The first step should have taken place before engine disassembly, identify Mag & PTO barrels. Clean everything with iso alcohol and dry out completely. Paint all interface surfaces with dye (you can use permanent marker in a pinch). The next step is to assemble the upper case to the jugs without a base gasket. First attach the Y-pipe to the exhaust ports without gaskets to establish good alignment between the 2 jugs (installing the head won&#39;t allow access to the cylinder barrel bolts). Line up the cylinders to the base as best you can to center the case inlet ports to the transfer ports on the jugs (putting a little electrical tape around the base bolt shanks before you screw them in helps alignment). Torque the cylinders to 15 Ft Lbs. This should be enough clamping load to marry the pieces and distort them to what is considered normal. Now index the cylinders to the base using whatever means you have. I always stamp an X on the front and rear of both cylinders across the base gasket parting line between the case & jugs.

Attached: the cylinder base inked

Attached: Dry assembled and ready to commence scribing

Once the upper and lower assemblies are fastened, the next step is to feel the alignment of the upper case&#39;s transfer port bowls compared with the port openings on the cylinder bases. It&#39;s preferable to have a little bit larger cylinder port than case bowl (if that&#39;s what you found consider yourself very fortunate cause it usually never happens!). Now using a machinists scribe (a pair of dividers from your grade 11 geometry set will do) preferably one with a 90 degree bend on one end, scribe a line from the larger component to the smaller one in the machinists dye you previously painted the parts with.

Easy does it, your only trying to scribe a thin line in the dye!

Attached is an image of what the line should look like. &#33;!! If you aren&#39;t sure about a line, DON&#39;T ASSUME!!!. Re-ink the part and start over. There&#39;s more jugs in the recycler due to: "I thoughts" than anyone can imagine. Once metal is removed, it can&#39;t be put back! (unless you have access to to NASA&#39;s molecular metallurgy department). Some port shaping & porosity issues can be repaired with high quality Devcon aircraft dent filler, but that stuff costs $45.00 a tube. These lines are your cutting limit. The best way to start cutting is to take Idooski&#39;s advice on cutter selection. I use high quality medical grade stainless steel burrs which aluminum doesn&#39;t stick to. My best advice here is to grab some scrapped motor parts from your friendly neighborhood dealer and practice on them before you set about your prized possessions (I got lucky, Idooski loaned me his jugs!). One good trick to cut aluminum castings is to cool them in the freezer, just pack your parts in next to that old pickerel your wife doesn&#39;t know what to do with, then let them sit for a few hours. The condensation that forms as your grinding acts as a coolant /lubricant for the cutter. Be sure to clamp those parts down to a non slip surface. A great product for woking on stuff you don&#39;t want to marr is the thick clear urethane verticle blinds used at loading docks to keep the cold out during the winter. It is soft enough to conform to most parts and give a good base to clamp to or make soft-jaws for your vise. I&#39;ll be reading the local newpapers for reports of a nation wide crime wave of loading dock thefts :hallo1:

Another

Last One, Stay Tuned!! :D

Originally posted by Thumbdoctor@Aug 4 2003, 10:27 PM
The next problem is with the reed cage, a couple of petals aren&#39;t seating causing delayed crankcase pressurization (up to 20 degrees crankshaft rotation to close those suckers !). There should be an airtight seal between petals & cage without too much tension on the petals.
I was always under the impression it was ok to have a little bit of light showing. after reading my new snowtech mag today, reed q+a section.they say reeds need replaced if there is more than .020 inch off the reed block.I know ideally what your saying is best.I also know manufacturing leaves much to be desired when it comes to getting you there.

Thanks for the update dooman!!. I also read the reed Q & A article, well written. What I was pointing out with Idooski&#39;s reeds was that only 2 out of the set weren&#39;t seating which usually means trouble. The OEM reeds have a spec which relates to all reeds in a cage. Another issue we might as well get out in the open (first brought to light by Idooski) is a cycle overlap (short circuit) between the exhaust side ports and the front two inlet windows See Attached short circuit.jpg (Arrow pointin at exhaust side port). I have discussed this matter with a few folks in the biz and have come to the agreement that in isn&#39;t anything to get worried about. Essentially, as the piston reaches TDC, the window cut into the piston skirt uncovers both the front transfer ports and the exhaust shuttle ports at the same time. Keep in mind that the piston is at maximum stroke (combustion is building) and whatever energy from the previous exhaust cycle has dissipated into the pipe. Where this cycle transfer becomes problematic is when the tract becomes open through poor piston design when maximum crankcase compression or exhaust back pressure is achieved. This can be complicated by pistons designed for universal installation or have been modified to fit which have cut aways or embossments to allow shorter (lighter) wrist pins. See Attached jobber.jpg. The stock Elko Piston has no such trickery around the pin location allowing an un-interrupted inlet cycle. See Attached Stock Elko.jpg

This is a piston removed from a 800 with serious midrange lean out. Can you guess why???.

Here is a stocker

from what it looks like to me the intake charge is blowing right out the exhaust via the cut out on the piston..

The intake charge could get out there, but what happened with mine was the exhaust was getting pushed back into the case and diluting the mixture.

Idooski,

How did you arrive at the fact the intake charge was being diluted?? Was this with twin pipes??

Back at you with what&#39;s been going on with the 800 basement. Attached Rail~delete.jpg Illustrates what the inlet bowl should look like with the oil rail removed. You will note that there is a somewhat large collector at the end of where the rail used to be. I may fill that to gain back some lost case volume but the jury is still out on what method to fill it (welding Yikes!!) or epoxy aluminum. In the past I&#39;ve used aircraft dent filler with good results but these series III mills are a lot stiffer and more stressed than the older heavier castings. Some of the new additives being blended into modern fuel contain thinners that can potentially weaken the chemistry of epoxy resin based products. I&#39;ll do more research on that!. Welding is the only sound alternative. It&#39;s both expensive and risky, too much heat, warped case. Not fast with the wire, crankcase ventilation.

Another image

A lot of you will no doubt use the base gasket as a template or to transfer the dimensions from one part to another. That&#39;s good but understand all gaskets are dye cut in bulk. They are rarely accurate, more like cars, built for the masses none hand built. That&#39;s your job, to delicately trim the gasket(s) to match the components. I usually take a piece of 180 grit aluminum oxide sand paper to clean up the inside edges. Don&#39;t dwell on the same spot too long as you will "fuzz" the gasket. It&#39;s better to tim the larger areas then sand or the gasket fibres will separate leaving the gasket porose and prone to failure as oil creeps in the edges. Lastly, seal the edges of the trimmed gaskets with lacquer (nail polish works).

One area on 800 series III base gasket to be weary of is the rear biased cut away on the two transfer bowls Attached Base~gasket.jpg. The arrows point how far back these cut aways are with no corresponding cut away on case flange or cylinder bottom.

&#33;!! Don&#39;t be fooled into cutting this material away from the upper case half see Attached Dye~proof.jpg this will illustrate what the difference in the gasket will lead you to remove but in effect you are compromising the rigidity of the casting to gain nothing. The rear deck of the cylinder doesn&#39;t have a lot of strength in this area because the reed box leaves the casting thin and wide open. The gasket is open there to allow better clamping load of the rear flange better securing the cylinder base gasket. :sly: There is a better way to match this area which I&#39;ll cover.

A better, more accurate way to match the rear case to cylinder interface is to lay the base gasket onto the bottom of the cylinder. Observe where the transfer bowl opening really ends. With a pencil mark the rear most edges of that opening on the gasket see Attached Bowl~profile2.jpg. Make sure you mark the inside edge of the gasket so you can see this reference when you flip the gasket onto the crankcase.

Now lay the (marked) base gasket on the upper case and see where the reference mark falls. This is the true end of the cylinder port. This is how far you&#39;ll need to blend.

Now after the layout is completed, double checked and you are all fired up with that dye grinder and burr. Start at the layout marks first, working your way down to the inside of the bowls. Check your burr for build up frequently. Any feeling of vibration on the grinder (or flex shaft) is your first clue that there&#39;s some aluminum stuck to the bit (Too Hot!). You should use a cooling / lubricating agent to better remove and control your cuts. I generally use motor antifreeze as it has good viscosity, cooling properties and won&#39;t allow cast iron parts to rust. &#33;!! Using A/C powered dremel type motors this poses a danger of shock or wrecking your motor drive if it gets wet, so use appropriate caution. To deliver the coolant to the working area, first put the part your cutting into a plastic pan(metal ones mar the gasket flanges) and clamp it down the work area (Quick Grips work well here) then attach a piece if 3/16" ID clear vinyl hose to a bicycle water bottle (Gatorade bottles work) and attach a strap on the bottom to hang it up see illustration. Voila! coolant supply. Do all your cutting in gentle sweeping strokes. Work against bit rotation (material should eject ahead of the burr) to smoothly cut the material as "back stroking" will "pattern" the finish leaving you more clean up work after.

Here&#39;s the hanging strap.

As I said in a previous post, use burrs with a ball end or bullet shape working into rounded areas. Squared off bits will gouge the inlet bowls. Start at the layed out areas and cut to about 1mm inside the lines leaving room to clean up with sandpaper. The best machine abrasive to grind aluminum is sanding tubes in various grits and sizes. You&#39;ll need a few of them to clean up some of the carnage left by the cutter. Machine sanding needs to be done dry working in a figure 8 pattern to avoid over sanding any spot. The best practise is to never stop moving the tube. Once you have worked through the bowls up to the fine grade paper, now is where some real work starts, To complete the surface you will need some &#39;Wet or Dry" silicone paper in 400, 600, 1000 ,1500 , 2000 grits. They are available a most body shop supply houses. This procedure assures wall straightness and removes lumps &#39;n bumps from previous work. Place part in plastic catch pan and cut sand paper into small 1 x 2" rectangles. Starting from the roughest grit (wet) clean all ground surfaces in X or figure 8 pattern. What you are trying to accomplish here is smooth transition from the freshly ground edges back to the original surface. The experts say that you do not need to have a polished finish on all surfaces, just straight and well blended contours. I personally like to polish my work to check to the enth degree for port shape and wall contour. To get the same port and wall finish as the original surface you can media blast the work with walnut shells or plastic shot. I have never had any issues on two cycle motors with polished ports. I, contrary to most people have had issues with epoxy resin based fillers and glues falling off into the intake tract. I&#39;m not saying that they don&#39;t work but in the hostile temperature spread that snowmobiles operate in and the additives in modern gasoline, I wouldn&#39;t chance it!!. Moral of this story, be conservative with the cutter don&#39;t hog out everything as large as you can, we only need incremental flange matching to get the job done &#33;!! Attached are photos of Idooski&#39;s uppercase matched, chased and ready to pack.

3/4 view

Bottom

One final note on the lower case: take extreme care washing out all pieces after grinding. Use warm soapy water and a brush, clean out all small passages with pipe cleaners. I use a dishwasher (don&#39;t tell my wife) with mild detergent. &#33;!! Don&#39;t use dishwasher or any chlorine base detergent as they will permanently etch the surface of aluminum parts. &#33;!! Never sand blast (using aluminum oxide or any stone based media) parts or the grit trapped in the surface of the metal will release as soon as your freshly ported rebuilt mill warms up. &#33;!! Never clean freshly ground parts in hot water for the same reason as above. Follow these simple rules and there will be no unpleasant surprises come 12 feet of snow. :thumbsup:

pores in the metal ??? ,just kidding. I am a heat treater so I understand.thats great , I really never thought of telling anyone to watch it while grinding.this is a great thead,I hope for idooskis sake it runs better than last year :p ,or he will have to get out donnas rev to beat me. ;)

any updates on this project yet?

Originally posted by dooman@Sep 4 2003, 05:00 PM
any updates on this project yet?
Dooman,

Stay tuned, I&#39;ve been side tracked researching a Holy Grail of another sort "THE RING THING !". I have been away from my beloved laboratory. Actually I&#39;ve been to visit Idooski&#39;s business and have to say I am DOOly impressed. I believe given set up time, Keith can tackle any machining project. I know where I&#39;m sending my tools for tune ups and skilled machining needs. &#33;!!

Thanks for the pat on the back doc.

To be honest with you, I think ol&#39; dooman is starting to sweat it a bit. :p

I think thumbdoctor is great at details but don&#39;t start a business lol. You ask why?? Because your to good and detailed to do joe blows wok at a resonble cost. lol. You&#39;d have to charge a us our first born (mine would be worth two port jobs she&#39;s so cute lol) for your work. I must say you&#39;ve been extremely detailed in this whole thread. I know Keith is salvating in anticipation of running his beloved sled again. :D

Originally posted by Sled Dogg@Sep 5 2003, 12:26 PM
I think thumbdoctor is great at details but don&#39;t start a business lol. You ask why?? Because your to good and detailed to do joe blows wok at a resonble cost. lol. You&#39;d have to charge a us our first born (mine would be worth two port jobs she&#39;s so cute lol) for your work. I must say you&#39;ve been extremely detailed in this whole thread. I know Keith is salvating in anticipation of running his beloved sled again. :D
My first born is already on the way north. :p

Originally posted by idooski@Sep 5 2003, 12:07 PM
Thanks for the pat on the back doc.

To be honest with you, I think ol&#39; dooman is starting to sweat it a bit. :p
sweat ,nah after all if thats the case nicks motor is for sale and we already know it runs hard ;) .he bought a new mod 800.still the 700 just need race gas :p .

Well, one cylinder is complete. I&#39;ll start with the reed box and work through. First I relieved the area where the reed stoppers were making contact with the roof & floor of the box. I then straightened out the sides of the box, paying attention the the shape of the two side case entries. You will notice a lot of casting flash and general lumpiness of the passage. I chose to do an aggressive job of straightening the outer walls of the jug and remained conservative on the back & sides of the cylinder barrel. Remove too much material here and you end up with a thin cylinder wall (not good !). I also took the strategy of lowering the center boost port to give the mixture a clean path into the crankcase behind the conrod. Some port designers remove the entire lower port section right down to the gasket flange. This, in my opinion, doesn&#39;t leave anything to support bore from becoming oval under high load / stress (keeping in mind the barrel is only plated aluminum with a 6mm wall thickness). I suppose this practice is more in line with cast or nodular iron sleeves which are sturdier. I left a 8mm bridge at the bottom of the barrel to retain some of the designed in stiffness.

Another:

For those of you who want to know "What&#39;s Up" with reed spacers, look at the rear transfer port&#39;s path when the stock reed cage is installed. The reed stopper obscures half of the port. This is why some people choose to install spacers with stock reeds. Spacers are not nessasary with most high performance reeds which replace the stock stopper with a rectangular plate which resides under the reed retaining screws. Most aftermarket reed valve assemblies are designed shorter to aleviate this design issue.

Here is another view of the lower profile of the rear transfer port. I chose to retain Rotax&#39;s inverted D profile in the bottom edge of the port as it reduces chopping pulse created by the piston skirt closing the port suddenly on it&#39;s downward stroke.

Moving around to the lower portion of the side transfers you can see the entries are smoothed out to match the upper case. If these are slightly larger than the base before you start to cut, don&#39;t spend a lot of time trying to match them exactly. Being slightly larger helps two ways. First, It allows for a little movement when the jug is installed (torqued) on the base. Second, the slight step biased towards the bottom provides a small reversion block. The port walls should be as straight as the casting will permit heading north to the port window ducts. Don&#39;t be tempted to Knife Edge the inlet port dividers as this will upset the flow rather than reduce restriction. The air flow will work a lot better if these are left rounded like an aircraft wing&#39;s leading edge. These dividers also provide support to the cylinder barrel keeping it round. Keep that in mind if you are considering thinning them. On these particular castings, the plating had migrated quite far into the port windows and transfer ducts right from Rotax. I chose not to spend too much time grinding out excess plating. Instead, I cleaned up the ducts which direct the incoming charge. &#33;!! Note: be extremely careful cutting (or grinding) around the port windows. It&#39;s easy to glide over the hard nik plating and suddenly gouge the soft aluminum creating an uneven window profile or worse, slip and destroy the bore surface. Preventative measures here are to: 1) Mask off areas on the cylinder bore as close as possible to the port windows using plastic tape or gaffer tape (thicker and better quality than duct tape). 2) Clamp the cylinder down in a vise using soft jaws. 3) Cut close to but not onto lay-out lines then finish using fine sanding tubes. 4) If you are using a Dremel tool with a 90 degree adaptor, make a chuck nut protector out of a 1/4" piece of 3/8 ID vinyl fuel line slipped over the top half of the chuck clamping nut (this protects your job from undesirable scratches when the chuck hits the work piece). 5) Fabricate or purchase a foot power control or switch as you will need both hands free to work with at all times. 6) When working on inlet port windows, place the tool into the port window before you start the grinder (It&#39;s too easy to nick the cylinder wall trying to feed a spinning burr or stone into a small target). 7) Select correct spindle speed before starting. Too much speed will burn or melt the aluminum, clogging the burr. Too little spindle speed will stall the bit and gouge the surface or injure the operator (practice on a scrap part first). &#33;!!

Using sweeping strokes, try to remove as little material as possible each time (this will assure straightness). Do not change the angle of the port entries into the cylinders (a lot of thought went into getting the flow just right). Only remove casting flash and bumps in the duct area. Chamfer the windows carefully either manually using a rifling file moving from the outside (cylinder bore) working into the port window paying attention to the horizontal chamfers on the square inlet ports. These chamfer profiles are best done .406mm (about .014" - .016") deep and 1mm (about .040") tall. On square vertical port sides, just remove sharp edge. Finish the chamfers using strips of oiled 400 grit crocus cloth (cloth backed emery) drawn through each plane of the openings. Using a die grinder (or Dremel type tool) use a small diameter 180 grit (wet) grinder and slowly start at the corners and work towards the center of the horizontal chamfers at about 75 degree angle the follow the same sanding directions as above. I will describe exhaust chamfer finishing later as it is a different process.

Another:

Wow you have done an amazing job describing your work.
The hands on advice and tips will be invaluable

Thankyou

As a newbie to the engine tuning scene I was wondering if you could give some reference to the terms and spacial orientations that you refer to in your posts. If there was any way to label the picts and show pre and post pics it would really help out.

This is a really basic ?? but am I correct in my assumptions that your work on the porting is to improve the flow of intake and exhaust mixtures into and out of the cylinder?

Keep it coming please :withstupid:

Originally posted by me&myMXZ583@Sep 8 2003, 07:53 PM
As a newbie to the engine tuning scene I was wondering if you could give some reference to the terms and spacial orientations that you refer to in your posts. If there was any way to label the picts and show pre and post pics it would really help out.

This is a really basic ?? but am I correct in my assumptions that your work on the porting is to improve the flow of intake and exhaust mixtures into and out of the cylinder?

Keep it coming please :withstupid:
me&myMXZ583 and all,

The object of this exercise is to increase V/E (Volumetric Efficiency). In simple terms, an internal combustion engine whether it&#39;s 2 stroke or 4 stroke cycle is just a pump. The more air / fuel you move into the combustion chamber, efficiently burn it, then dispose of it, the more rotational power it produces. An engine converts combustion heat into kinetic energy. Now this is true only to a point, it is virtually impossible to reach 100% V/E at atmospheric pressure. There are mechanical pumping losses to consider, air density (Altitude) and a myriad of other physical laws to contend with. By external means of adding atmospheric pressure through Turbo or super compressing the air entering the engine, higher V/Es and copious amounts of HP can be achieved. Nitrous Oxide (NOS) can also improve V/E by adding more oxygen molecules to the air/fuel mixture through a cooling gaseous vapor thus increasing air density. Add too much NOS without adequate supporting fuel molecules and the results are explosive resulting in ventilated piston crowns and cylinder heads.

What we are doing is providing the Air / fuel mixture a less restricted path from the carburetor&#39;s mixing chamber to the combustion chamber while keeping the mixture in suspension. In long tract intake systems carrying wet mixture (Air / Fuel) it is preferred to have a somewhat rough (satin) finish on port walls, roof & floor as this creates turbulence keeping the mixture stable. The fact that the port walls are wetted by fuel also aids in cooling the mixture to a point. On short tract intake systems there are different theories. Some say small volume and polished inlets = peak HP. Some say quite the opposite. The spin on large volume inlet tracts say there is more than adequate reserve for broader torque bands. The other things to consider are connecting rod length (=Piston speed) bore and stroke. These are all compromises engine designers have to consider. On this project we are not going to do anything radical, were just going to correct some tolerances over looked through "Mass Production" and improve V/E using tried and true methodology leaving the really radical stuff to the folks who have to rejet every ride !. I will provide a list of terms an explanations at the end of this forum to help the folks who are new to this exercise. There are some before photos provided by Idooski at the beginning of this thread.

i am certainly enjoying this project. One thing That i&#39;m having trouble with is the cutters and stone you are using in differ areas of the engine. Can you list a discribition (picture) of what you are using in certain areas. this would also fill in my missing blanks that I have. Also which model dremel should be used and does it need to have a foot operated speed control? Thanks for a very good project.

Originally posted by oldman@Sep 16 2003, 09:25 PM
i am certainly enjoying this project. One thing That i&#39;m having trouble with is the cutters and stone you are using in differ areas of the engine. Can you list a discribition (picture) of what you are using in certain areas. this would also fill in my missing blanks that I have. Also which model dremel should be used and does it need to have a foot operated speed control? Thanks for a very good project.
oldman,

The Dremel model most popular for this type of project is the #395 Type 4 variable speed. It&#39;s cheap and reasonably durable. Accessories should include a 35" flex drive, an 90 degree adaptor (only good on 3.5" or larger bores). I use a variety of High Speed Steel Burrs to achieve different results. A foot switch is a great way to have both hands free to concentrate on the expensive part. See attached

A) tungsten flame shaped helix flutes, used to shape port window openings in cylinder barrel. advantages: tungsten can be cleaned using Muriatic Acid and keeps it&#39;s edge. Will cut nikasil. Excels at high tool speeds and rarely catches or skates.

B) High speed steel 1/8" ball helix flutes, used to clean up port ducts (90 degree bend) at top end of transfer entering into cylinder. Advantages: End of this burr will cut when pushed into tight radius bends as described above.

C) HSS 1/8" - 1/4" ball ended taper straight flutes, used to enlarge tight radius port entrances at base of cylinder. advantages: Ball end prevents gouging created by flat topped burrs. allows gradual enlargement of tight corners.

D) HSS 5/16" flame profile helix flutes, used for large radius blending of inlet bowls at upper crank-case locations and tunnel ports in R/V blocks. advantages: same as above.

E) HSS 5/16" flame profile straight flutes, same as above

F) HSS flat profile ball ended straight flutes. used for straightening port ducts and any irregularities in castings. Advantages: ball end prevents gouging, will operate at a vast variety of chuck speeds and can be use for multiple tasks.

[B]Note: the major difference between helix and straight fluted burrs is a helix removes less material and leaves a smooth finish, it&#39;s more forgiving to a beginner. Straight fluted burrs remove material rapidly and will leave a pattern finish, have the tendency to stall tool or catch work.

The type cutters for beginners to avoid are flat topped deep fluted burrs Attached Photo, in the wrong hands they can do more damage than good !. Even in a skilled hand these create a lot of revisiting with sand paper to clean up the clean up!. As far as stones, select a 180 - 400 grit variety in different shapes. Also purchase a cheap sharpening (lapping) stone to dress the rotary stones before and after use. You will need a constant flow of coolant when using any kind of abrasive stone on aluminum as aluminum tends to clog the abrasive. Muriatic Acid will clean most stones (disintegrate some !), be sure to do this outside away from yourself or any ferrous metals in your shop as the fumes will cause them to rust immediately!. The best advise I can give is to practise on some scrap pieces before you commit to grinding the main event. You will need to shape some stones yourself ( using the forementioned shapening stone and oil) to match the shape you are working on. Never push the grinder into the work, you should work in sweeping strokes without stopping the bit allowing it to pull itself onto the rough castings.

Attached are just some of the burrs, discs, sanding drums and stones I use when doing a job. The important thing to decide is quality, cheap bits and stones vibrate, comprimising your hours of work and ruining your rotary tool.

Coarse, medium and fine sanding drums work great cleaning up any pattern left by metal cutters. Again, never dwell in any place, keep moving the tool!
A lot of straightening and smoothing needs to be done by hand progressing from coarse 320 grit Wet or Dry emery paper down to 2000 on ports you intend to polish. Sanding works best in a pan of water. The water lubricates the paper and flows away the removed material (on cast sleeved jugs be sure to oil barrel after thoroughly drying bore).

Finish polishing can be achieved by using abrasive impregnated rubber bits (they go by the name Cratex). these sacrificial rubber bits are available in fine and ultr-fine grits. Be carefull when getting to the end of these bit&#39;s usable life as the shank will scrape your freshly polished work! (Go back to START: do not collect $200.00).

The final polished (optional) finish is processed using felt bobs and jewelers rouge (compound) Brasso brand metal polish will also do.

More to Follow

;) Thanks for the great info. Once I get my shop done I&#39;ll be able to start . Thanks again for a great thread :thumbsup:

As promised for all the beginners & shade tree wrenches, I searched high & low and found a site which defines all the terms (jargon) I use to describe the procedures and components of a two stroke induction / exhaust systems.

Two Stroke Glossary (http://www.2-stroke-porting.com/terminology.htm)

Enjoy, :)

Thanks Dr.
Great info on the 2 stroke working and terminology

Do you want your own area on SW for this project. Just PM me if interested,

The main exhaust port on the series III should be carefully inspected for port height and width. Any work performed on this port should be restricted to slight widening of main port and side ports. Do not Raise the roof of the port window unless you are bent on building a drag machine. Opening the exhaust port sooner will aid in high RPM operation but low and mid range will suffer. The route I am taking is to leave the height of the exhaust port window stock and reshape the top contour of the window&#39;s corners. The attached layout should illustrate the differences between stock (red line) configuration and projected changes (black line). Note: the area at the bottom rounded corners (A) of the two exhaust side ports should be left in stock form as any material removal here contributes to the "Cycle Sharing" issue discussed in the other thread. The Main and two side exhaust port windows can be safely widened 1mm (side ports widened rearward 1mm and main widened 1mm on each side). The best way to perform this is to start by making a template out of good quality cardboard and make all final cuts using a sharp layout knife. Those of you who purchased a porting kit, just follow the enclosed instructions for template installation. The layout should be scribed onto machinists dye previously painted around port windows. I use sheet plastic .050" thick to make templates keeping in mind that the thicker the template, the harder it is to manipulate into the cylinder to transfer the layout lines.

Once the port window outline has been laid out on the cylinder, start grinding out material. For beginners, I would strongly recommend avoiding aggressive burrs and progress slowly using sanding drums. Start with medium grit and work from the exhaust pipe side into the port grinding close but not touching the layout lines. Leave about .5mm material for finishing with fine grades. Always work against the rotation of the tool opening the window and pulling the new opening 10mm back into the exhaust duct (long portion of exhaust passage). Once the profile of the layout is completed using the rough abrasive and is approximately 10mm into the duct, you are ready to start blending. The object of this exercise is to smooth the freshly cut window opening outward to the duct

One thing to keep in mind while blending is that exhaust gases are continually expanding as they leave the combustion chamber, so try to progressively expand the port as close to original configuration as possible. This porting is planned to work with a highly efficient single pipe or a tight twin pipe set up with a target RPM max as close to stock as clutching will permit. Buzzing the engine into the rev limiter will not fit the intended spirit of these mods. We want this motor to build power within the parameters of stock max RPM and clutch heavy to make it stay there !. Here is what the rough finishing will look like. As said before you can leave the inlet ports rough but the exhaust should be finish polished.

Now that I have you going "hog wild" with you chainsaws tryin to do it as fast as you can because snows a comin !!, I want to bring something really important to your attention. There are two cooling passages that are drilled from the top of the cylinder and opening into the base at the front (exhaust) side of the jug.

These passages are fed coolant from the pump and flow upward into the jacket around the exhaust ports and continue into the cylinder head. Do not pull the exhaust side port window openings back any more that 10mm. Do not remove too much material from the outside surface of the exhaust side port ducts or you will discover on your maiden voyage you have coolant injected exhaust. Due to build tolerances, there are differences in available thickness in between the coolant passage and the side port ducts. What makes this worse is that the casting core (Parting line) runs horizontally across the cylinder at this level. Where casing lines of upper and lower assemblies meet there is always some porosity in the aluminum so a word to the wise goes a long way !

Finally, to finish up on the exhaust port I would recommend using wet or dry emery paper starting at 320 grit moving all the way up to 2000 grit as this will make life easier on the felt bobs polishing. Place the jug in a plastic pan and add about an inch of water. Cut the sand paper into strips one inch wide by four inches long. Using rubber gloves pull the strips of paper from the port window out into the duct finishing at the y-pipe gasket flange. Alternate sand paper regularly putting used pieces back into the water. once all the ridges and small grooves are gone and you are working with 2000 paper, add a few drops od dish soap to the water. This will provide some lubrication to the ultra-fine paper and leave an almost perfect finish. Send the wife or significant other on an errand (or out with her friends), then put the jugs in the dish washer using mild dish soap as a cleaner. Once the jugs a out from the wash you will need to perform a final inspection, checking for any rough spots, carbon stuck in the side ports and general straightness. Now with your rotary tool set a the lowest speed and a felt bob installed on the chuck, load the bob with some jewelers rouge (compound), Flitz or Brasso, start applying the compound. Work on the tight spots first then complete the job at a higher chuck speed. You want to develop some heat on the final pass to assure the polished finish will not tarnish or have combustion residue adhere to it.

thumbdoctor, very nice work , thanks for sharing it with us. I&#39;d like to add a warning about making the area too thin that divides the main and side exh port. I&#39;ve found these hairline cracks on cyls that did not look to be overly done. One of them the crack eventualy migrated and showed up in the nicasil. Not sure if it is stess or heat that caused . Hopefully my (lousey) pic will show what I mean. Thumb, are you raise the side ports to the main height?

forgot the pic

Hillpounder & all,

I leave the side exhaust ports at stock height which is 3mm below main port. The center or main port has the benefit of the RAVE valve to effectively lower its height during low RPMs, the side ports don&#39;t. I have seen 800s with the side ports raised on all out drag racing rigs employing open twin pipes, very strange sounding until the valve opens, almost defeats the object of having a RAVE. I&#39;ll have some comments and photos on the Y-pipe for those who choose to stay single (pun!!).

Thumbdoctor... Everything looks great!!! I&#39;m just a-wigglin&#39; in my seat with anticipation.

I am proud of what a great job you did with my parts as well as the in depth descriptions of each operation. I&#39;m sure everyone appreciates your candor all during this portion of the project. Not many people would have gone to the lengths that you have, even to explain what tools to use and how to use them. This is all invaluable information that is safely filed away.

But don&#39;t go thinking that you are all done with me. I hope that you will share your knowledge throughout the rest of the project. Lord knows I can use it.

I have the lower end ready and waiting. Just need to get the sled off the ceiling and we&#39;ll be all set.

Don&#39;t think that this is the end of this thread. Thumbdoctor may have more to add and I&#39;m sure that there are still some questions out there. Keep the information flowing folks.

Thanks again Doc!!!!!

hey doc , all i can say is that is a beautiful job ,i can&#39;t wait to see them in person at idooski&#39;s shop, and your posts on porting have been excellent .

Great job on the project!!!! How much power do you feel the improved flow will increase? Thanks for the excellent photo&#39;s

SKI-POOP
SWRules

Were focusing on usable torque here, horse power will be better than stock but that gain also depends on other parameters such as CR, piping, carburation and ignition timing. I don&#39;t want to start a "bench race" on numbers here. When Idooski assembles the mill and dials it in (stage tuning) we will make estimates then based on real world scenarios on a step by step protocol.

Forget estimates strap it to a a chassis dyno keith and let&#39;s seee hte curve&#39;s. Bet it&#39;ll be a fun winter for you this year!!

[quote]Do not Raise the roof of the port window unless you are bent on building a drag machine.

This makes me a little nervous being the sport port templates for my machine raised and widened the main exaust port. The templates raised my ports about .050 of a inch. I have not yet got a chance to run it yet but i hope this isnt going to hurt my bottom end to much. What do you think Doc? :cussing:

mxzjunky,

What I meant was do not raise any port windows if your going to shim the base up and use a high compression head. The porting templates you mention will not adversley impact bottom end. The target RPM you need to clutch for with stock single pipe and an aftermarket can will be 7800-8100 RPM, keep it to the lower end because the rev limiter is at 8350 so if you hit some slippery stuff you may bounce off the limiter.

wow thats a relief, :D thanks for clearing that up for me Doc. Just waiting for snow so i can start playing with the clutches. By the way this whole discussion is great Doc and Idooski I think you guys are awsome for sharing your knowledge with us rookies. Thanks Again, Andy SWRules

Thumbdoctor-you had mentioned something about y pipe mods in an earlier post-any more to say on that topic? Thanks

Originally posted by Sled Dogg@Nov 18 2003, 10:46 AM
Forget estimates strap it to a a chassis dyno keith and let&#39;s seee hte curve&#39;s. Bet it&#39;ll be a fun winter for you this year!!
you paying the bill caleb? :p I bet he wouldn&#39;t have a problem doing it if you are.

Originally posted by rangelec@Dec 14 2003, 11:48 PM
Thumbdoctor-you had mentioned something about y pipe mods in an earlier post-any more to say on that topic? Thanks
On the Y-pipe I MIG welded up the outside of the flanges to give me additional grinding room (sorry I don&#39;t have finished product photos). The flanges were then ground out to match the exhaust port outlets. On Idooski&#39;s y-pipe the ball joint was in rough shape probably caused by a soft engine mount or too many well hooked up WFT launches with some weight on the machine. I elected to use bronze for the ball seal as it acts as a bearing and reduces future fatigue. Lastly, I polished the entire exhaust tract in the y-pipe to help the hot gases get to the expansion chamber in proper time. When the y-pipe is married to the expansion chamber, be sure to use copious amounts of High Temp Copper RTV to seal the joint. A good trick to reduce the chance or the RTV shearing when the machine is worked hard is to seal it up without the springs retaining it and the expansion chamber shimmed up about 3/4" to simulate real world engine movement. Let the sealer dry, remove the shim then install the springs. Check all motor mounts and exhaust springs for looseness. Install a motor brace if you like to holeshot the sled and can&#39;t steer clear of the Twinkies in the off season.

perhaps Idooski can import some photos of the finished y-pipe for those of you who are interested. I inadvertently deleted mine :cussing:

Seasons Greetings All &#33;!! :christmas:

Does this sled run yet? What were the results?

Want to know update on this bad boy.

is idooski even around anymore? :dazed:

Yepper, he is still around. I talked to him the other day and he said he had been upside down at work. :cussing:
I dont think the ported motor has even been fired up as of yet, I know it is in the chassis and most all is hooked up. I think he is waiting on a 03 non-dpm mpem. He converted everything on the 02X to all 03 stuff and thats why he needs the new mpem.

Brian


Originally posted by Dynamo^Joe@Sep 1 2004, 01:08 PM
Want to know update on this bad boy.

is idooski even around anymore?* :dazed:
342853

Thought I would bring this to the top as the season is coming upon us again. We never did hear how it worked and if the motor stayed reliable.

I believe this project may just come to light in the next few weeks. Stay tuned!
The sled has not been finished yet, but just may happen soon.

Brian

I know it&#39;s an old post, but i&#39;m planning to install an 800 in the 440 REV. The 800 mill wilkl be well worked over. Any more comments to how this ran, tunning needs ect?

I know it&#39;s an old post, but i&#39;m planning to install an 800 in the 440 REV. The 800 mill wilkl be well worked over. Any more comments to how this ran, tunning needs ect?
[/b]

My life for the last two years has been just full of surprises. There has been no time to even get it running. Rest assured that I still have the project going and will have it on the snow this winter. I have done a lot with this sled that isn&#39;t listed yet which only added to the long list of things to be overcome to get her running. Stay tuned. As soon as I get my house renovation completed and we get moved, the &#39;02 is at the top of the priority list.

godspeed man!