I just finished cleaning up the ports on my 800 Doo twin./ I did not change the port hieghts and or shape but, I did clean up the entire flow path from the reeds to the crankcase to the transfers. I could not believe how much casting flash and poor casting there were in my cylinders until I started studying them and looking how to improve the air flow. I took alot of material out but, I also added some in the form of epoxy.
Has anybody else done this to there cylinders and if you did what was the outcome?

Here are a few pics:

another:

Last one.
If you notice, I had two ports added infront of the reeds to help flow into the crankcase.

Nice looking job. Did you blue print it while you were at it?

Wish I had some juggs to look at. :( :p

Were those ports done by dne? if so youre not going to believe the increase in power.As far as all the extra polishing(according to the gurus) you(and me also) wasted your time.I did the same thing on my mach z while i was putting in the shim kit.I bolted the top half to the jugs an port matched everyting then removed all the casting flash etc.I also polished the top half of the case and relieved the area above the reed cages.On mine the above mods were good for more than 10 mph in 500 feet.I personally think it was time well spent( about 30 hrs in total)Also if you need some clutching help i did up one of these last year and have a pretty good clutch system for those ported 800 twins.

John can you possibly help me out.I have a 02 mxz 800 done by DNE and cannot figure out the clutching for the life of me.THANKS...Eagle_17@attbi.com

Eagle how much do you weigh??and did you get the whole kit,ie modified reeds etc.

Originally posted by john breedon@Jun 8 2003, 08:01 AM
Were those ports done by dne? if so youre not going to believe the increase in power.


John, Kelsey at RK Tek did the ports for me. I had them done at the begining of last season. You are right they made a big differance. I also used Kelseys pistons, head, and 2mm shim. I did not like how the 2mm shim performed and after talking with Kelsey, we lowered it to a 1.2mm shim and machined new domes. I have not yet been able to run it since. While I had everything apart I decieded to go ahead and clean everything up and straighten out the flow path on the intake system.
With the 02 rer clutch, I fought it all last season trying to get it dialed in. The problem is that at between 90 and 95 mph the sled stops and will not go any faster. I had problems with the secondary actually lifting the helix off the ramps under hard accelerration and shift out fully and then slam back. It was beating the buttons to death. I now have found some secondary springs that I think will be the ticket. My clutching problems are another story that I will post in the proper forum :) .
As you can see in this pic that idooski took of me late last fall, the sled has alot of torque down low. I even had 27/43 gearing in when this was taken. If I can get it to pull like this on the topend, I will have one bad MXZ :D !

Hey john,


I weigh 225 and yes it has the whole kit..Thanks in advance

Eagle my buddie only weights around the 160 mark so youll have to change the pin weight a little.After trying Dons kit with the 280s(which we had no luck with) we went back to the 301(dont quote me on this)but they were the stock ramps for the o2 mxz800,200-320 spring,goodwin adjustable pins,again for his weight we went with 20grams of weight,but youll probably be down around the 18.2 to 19 gram area,the updated skidoo rer spring and after trying about 5 or 6 helixs we went with a straight 50 rer skidoo helix,27-43 gears and the belt deflection set to the tight side(track rolls when running on a stand)This sled absolutlly flies.With Dons kit it was still getting beat by f7s now f7s and zr900 are no problem.He also put 192 woodies with more than a half inch of penetration,it comes out of the hole like a house on fire.

Thanks John I really appreciate it!Does it matter if I get the helix from Ski-Doo or not?I usually get them from goodwin's but I don't know if they are coated or anything.

Not that the Goodwin Helixs are bad,its just that I have found it hard to dial in after running skidoo helixs.For instance my mach z would pull a 52 no problem,a 54-48 is my helix of choice,i tried a Goodwin 50 and it would over shift.I have tried goodwin helixs on my customers sled with the same result.Lets say you have a 50-47 and go to a 52-48 skidoo helix and it pulls no problem,then you try a similar 53-47 goodwin,it over shifted,tried a 54-48 ski doo no overshift.Im sure its because of the coating but once you start with one brand i would stick with it.Again its not a quality thing,and this is only my preference.

How do you go about cleaning them up? What did you use? Dremell tool or something similiar? How do you polish them? I would like to do a little work on mine, but dont want to screw it up. Dont want to go to crazy.

Originally posted by XCR583@Jun 16 2003, 09:37 PM
How do you go about cleaning them up? What did you use? Dremell tool or something similiar? How do you polish them? I would like to do a little work on mine, but dont want to screw it up. Dont want to go to crazy.
You can use a Dremel with flex cable for the accessible port entrances but you will need a 90 degree adaptor for the cylinder barrel. I don't think the Dremel 90 degree adaptor will last very long on this type of work. I use an old T & B dentist's drill with a home made chuck for 1/16 to 3/16 shank bits. It's funny how people suddenly take notice when I start this baby. I guess it scares most people who been in the chair for a root canal. There is some good tips onMacDizzy Two stroke Page (http://www.macdizzy.com) . Follow some common sense rules of thumb. Don't try to over do it !. The object of the exersize is to increase volumetric efficiency while retaining good scavenging properties. Cleanliness is paramount, don't leave anything to chance. Protect your sleaves with rubber tape around venerable areas incase you slip or break a rotary bit. Nicasyl or cast iron is not hard to damage with a misapplied tungsten rotary file. Intake ports should have some what rough finishes to promote turbulence. Attach cylinder barrels with head & exhaust y-pipe attached (to maintain alignment) to upper half of crankcase then scribe the dimensions of the larger transfer port shape to the mating cylinder tranfers. Exhaust ports can be polished & matched to Y-pipes. Go easy here. you don't want to raise the height of the exhaust port with a grinder. Be sure to chamfer all ports that have been clean up in the cylinder barrel. I pay special attention here using 600 grit croqus cloth and oil just round the upper ond lower edges off the ports. If you are replacing the piston rings, do a light hone to re-establish a cross hatch. The most bang for the buck on the R/V motor is gained through tunnel porting and there are quite a few different theories posted here. Good Luck. If you need help, just ask! :)

Thumdoctor, you described exactaly how I cleaned the ports up...Thanks.


Brian

Last one.
If you notice, I had two ports added infront of the reeds to help flow into the crankcase.[/b]
i am new at this porting isue. and i was wondering if i can turn my stock 02 mxz 800 jugs to h.o. specs or better. and how do they add the extra port holes

The added ports are done one a knee mill, or mine was anyway. The porting for the HO can be done to the non-HO cylinders. If I remember right, the HO cylinders exhaust port is raised, and the HO head creates a little more compression and a tighter squish band

I just got finished with RaceLogics Sport Port templated on a Doo 580. I'll be posting a article about it in the next couple of weeks. I have to go away this week, havn't even assembled the engine yet, just got the cyls done. Should really waken it up though.

this porting has deffinetly got me thinking.... will it also increase the "effiency" of the engine? driving it normally can a guy expect to get better mileage?

Yes it will, my ported 670 with 46mill carbs gets the same milage as a stocker I ride with.
But thats only when it is driven easy, start to pound on it and thats a different story