I will rebuilt my 2 1991 pantera and cougar that I bought for nothing last winter. And My first thought was to put wiseco in it. But After speaking to MR. Andre Bernard from Atelier Adrien Bernard, To have prices on crank rebuilt he told me from is experience that he would not put wiseco in them...He told me that is first choice would be Oem, second Kimpex and in last wiseco. Why? I don't know but its not a sale gammic because he does not sell oem and he does sell wiseco and he does not recommend them.
So Im all mixed up. And I would like to see what you are all thinking about this.

i always go with oem. for some reason in the past i have had no luck with the rest. now that was smoe time ago and im sure that the rest of them are much better now. but i would go wiseco before kimpex

oem price I got is around 150$ each. Wiseco at 127$ each and kimpex at 50$ each.
It does make a hell of difference in price at the end (I need 4 of them)...Both kimpex and oem is cast...would it be the aluminum alloy in that make the difference in price or just the name on them?..???if its for weight matching I can do it myself. I have acces to a digital balance that go 1 or 2 number after the dot in oz. good overall difference...between oem and kimpex...600$ to 200$.

The biggest thing with wisecos from what I understand, is to let the sled warm up fully and you have the correct piston to wall clearance.

These are a forged piston so the molecular structure is different than a cast piston. The forged expand at a faster rate than the bore, so if your not carefull, uncle squeeky will rear his ugly head!

I am going with wisecos for my 800.

only Time will tell

A nice alternative ,if they make them for your sled, is SPI.
They are coated, skirts and tops. Measure identical, in all that I have used.
They have worked well for me and others and usually run about $75Can with rings,pins and clips.

H.O.rider? You know where I can find a place where they sell them in canada??

In Saskatoon thet can be bought at Rec Supply and in Regina at Agri Sports (306 525 8366)

thanks..Do spi have a web site? I will be able to see if they have some for my machine...

SPI is made in tawian and is sold through different suppliers, kimpex is one that come to mind, though ALL kimpex pistons may not be spi? They are often sold as "OEM replacement piston" with no reference made to spi. One online canadian distributor that I know carries them is: www.royaldistributing.com


If you ask around as to their quality you'll get mixed answers, some have had very good luck, others haven't. Some shops I know will only use them in mild stock applications, older sleds. I also know other shops that are building mods with them too, so go figure.

As usual hillpounder is correct. Made in Taiwan, many people are scared off by that and the relatively low price compared to OEM or Wiseco. Keep in mind the info you get is based on personal experience. I have had better luck with the SPI's than I ever did with Wiseco's. I ran both in a twin piped mod 670 and the SPI's worked better for me. I know many who have used them and dont know anyone personally who had trouble.

I will email Royal on this to see if they have my application for those spi...

I have experienced it first hand, so this recommendation doesn't come lightly (or cheaply for me) Be very careful in choosing a replacement piston for your machine. I'm going to refer only to the Doo 800 twin. The stock piston has no recess around the wrist pin. There is a reason for that. If you use a piston with a recess built in to use a shorter/lighter wrist pin, you will short circuit the exhaust boost port and the front scavenge port. Both sides at the same time. NOT GOOD!! I'm hearing that with single pipes, the problem is not nearly as noticeable. But you put a good set of twin pipes on that produce strong signals you will experience trouble with a capital T. Trust me. If the cylinder stuffing pulse comes back too late, the case gets diluted with exhaust which in turn creates a serious lean condition which really doesn't appear that way when you check the wash. The carb problem is nothing compared to this. It can also build excess pressure in the case blowing base gaskets.

The Kimpex is a definite 'don't use'. At least on the 800 twin. I can't say for sure on the others, but I would certainly watch out for it.

Just be careful in your decision making process. Saving a couple bucks now could cost you a grand later. :devil:

I will maybe go with the wiseco's....I can have them from Fireball coating for 137$ each and they come coated. Any pro and con on coated pistons??

Originally posted by abc@Aug 21 2003, 07:43 AM
I will maybe go with the wiseco's....I can have them from Fireball coating for 137$ each and they come coated. Any pro and con on coated pistons??
I haven't heard of any instances where it has hurt anything.

The order is on the way...590$ for 4 2332M06800 wiseco pistons Coated. tax and shipping included from fireballcoatings. 2 of them on the 1991 cougar and 2 of them in the 1991 pantera. I will now need to tear down the cougar engine to ship the crankshaft with the pantera one. The pantera is already tear down. Will ship them for rebuilt to Atelier Adrien Bernard and to weld on the pto side to prevent wobble after a few thousand miles...After that we will have (me an my wife) 2 reliable machine totally rebuilt for around 3000$ including the price that we bought the sled. 350$ for the pantera (3500miles and blown)and 500$ for the cougar 4500 miles running). It was cheaper for us to go this way instead of buying a new machine, pay it on a few year...buy another...pay pay on a few year rebuilt the first one after paying the second one....etc...etc...So we will both be riding for cheap if the back hold on.... SWRules

Hope that you did not place the order yet......If you didn't I can get you the pistons Wiseco or Kimpex at a great price. The wiseco are about $65 US plus ship and the Kimpex are $42 US plus ship. These are for the complete piston kits (rings, circlips, wristpin, bearings...etc.) not just the pistons. Believe it or not I have had better results with the Kimpex. I sell both so I do not have a bias. Also if you need a professional gasket kit is is around $30 US plus ship for the Winderosa master kit.

If I can help you anymore please feel free to email me at Carpetrx@ligtel.com


Tony

Thanks Tony but Im im the great money valued nothing Canada and here the cheapest price I could have for wiseco pistons (with ring pin and clips) was 127$ and had to pay 2 taxes. now I will pay only one taxes and they come coated at 135$. I did not put kimpex because I did bought a sled before that had them inside the engine. And after only 1200 miles one of them simply exploded in the engine. There was nothing left under the pin...I did put wiseco after that and after the same milage they still looks like new and still there working. I could have kimpex for 50$ canadian. But I wanted to know the idea of the other rider here between oem and wiseco's. You are not the only one that told me that they would put kimpex instead of wiseco. ??? See I got no advantage to buy in usa. I did bought a exhaust box for the pantera from spikegary for 10$ us and shipping was around 15$ us I think. The thing cost me shipping included 49$ canadian. Yep the money order cost me as much as this.

Well there are some excellent posts up there. Just want to add my 2cents. The problem with wiseco is that the rings are usually thinner then stockers and the top piston landing is considerably thinner making the top of the piston very weak. Also I have heard that the pin which holds your rings from turning like to come loose and cause the ring to turn which eventually finds the exhaust port and pop the ring hangs up and smashes the top of the piston usually breaking the top off. As for kimpex I have never seen anyone have luck with them. The SPI's I would say is your best bet. For example, my 98 xc 600 blew up on me. So I did the same thing as you pricing pistons. I got a set of SPI's and just comparing them to the OEM's there was no difference at all the casting on the bottom side of the piston was identical and everything. But my guess is that they are OEM pistons that didn't come 100% into specs and were rejected for weight or dimensions but I never had problem. Then again I didn't keep the sled long after but have only heard good thing on them. Good luck with the Wiseco's ;)

Not a fan of wisecos but they are alot more user friendly in nicasil bores than iron. Personally Ive never had a failure or a poor running sled when using SPI or Kimpex stuff, for the average trail rider there a good value, if you are constantly racing or running the hell out of your sled Id say OEM would be my choice.

If the Wiseco's would be so bad they would be out of buisness long ago. I think they are good value for the price. I had bad experience with kimpex...Also once with oem but it was my fault...Anyway I did ordered coated wiseco and should have them Friday. I think I cant go wrong. Let's hope so...

Stay away from those kimpex TIAWAN pistons they are JUNK. WEISCO is the way to go. The problem encountered with weisco pistons are usually because of poor prep or machining practices before installation of said pistons. I use only weisco pistons because of their proven durabilty. When having your cylinders preped for your new weiscos bring the pistons to the machinest with the cyls. so they can be custom bored and honed to the individual piston. the weisco specs. are included in the box that the kit comes in. to many so called engine builders will purchase say 20thou over pistons and just bring the cylenders in to be bored 20 over well if the piston is off just a little it might be out of spec in wall clearance so have them custom bored to the individual pistons then hit the trails and lakes. :D

I assume SPI is an abbreviation for their company name, but what is this Taiwanese companys full name??

If your a doo guy, Cudney's pistons are the only way to go.

My sleds are both rebuild and now run well. cranks where sent to be rebuilt and welded by atelier adrien bernard and put 4 coated wiseco in them from fireball coating. Now only time will tell how long it will last.

i have wiseco pistons in my 500 indy and have had them for 2 seasons so far this year being the third, i have not had any problems with the wiseco's, the engine is still holding compression at 140lbs and have near 2000miles on the new engine. I do let the sled warm up for probably 5 to10 minutes before i ride, but i do that with everything i own my atv,car, outboard and sled. All i can say is that the wiseco pistons work good for me. Tim

I ordered a set of SPI pistons this week for my XC800...

I say that to my local dealer today, and he said that SPI pistons are the same than KIMPEX PISTONS ?????? Same companie but with different name... Not what i read here ??? And SPI are Silicone Aluminum Alloy and have a Teflon / Molybdenum Coating Pistons and have a Hard Anodized Crown... What about Kimpex, are they same ?

Someone know the difference between Spi and kimpex ??

i also have had good luck with spi pistons. a local shop down the road recomended spi.they put them in lots of customer sleds with no worrys with regard to relibility. they also put spi in there old school mod sled that is a twin rotery valve tripple based on a 2 521 rotax engines. so i put spi in a friends 04 800ho that was plaged with a broken ring and severe flaking on the good side. the quality appears great and they were cheap 140.00 for the factory piston and rings. 62.00 for the spi,rings,clips and wrist pin. i reused the factory pin due to the fact that they were tapered and the spi were not,and the factory pin fit better in the spi piston than the factory piston. there was less space that the pin could move side to side between the clips when installed. the sled has survived some severe beatings with a big guy to the handle bar. thing runs better than when it was new. i am a firm believer in breaking it in like you stole it. seat them rings tight,if it is built with the correct tolerences the sled will be faster than if you baby it. i am not saying beat your sled,unless there is a warranty behind you te he he. i guess i should put up a disclaimer of some sort at this time so i will not be liable for any issues. do not try this at home kids this is just for informational purposes as with my expierences and or others i have ben in close contact with.i have found discrepencys when dealing with information found, and try to only post what i doo know as true. a poll is a good way to see what works for the majority, but it may not be a good way to find the best info,as we all know the guy with the biggest ad campaign does not allways have the best product. dan

Heres my 2cents. "xc600" is right on the money. The Wiseco pistons have a problem with the ring locator pins. This pin is considerably smaller in dia. than stock pistons because of the thinner rings used. The expansion rate of the aluminium may also be at fault. What ever the cause the locator pin will fail. This has led to the ring rotating and snagging the exhaust port resulting in the total lose of piston and jug. Been there done it. I have seen this happen twice to my sleds. Both times the cylinder was wrecked beyond repair. I took my complaint to Wiseco and showed then the damage. To there great credit they replaced my jug and piston. This however took 6 weeks and my season was done.
The possible mechanical failure of the rings far outweighs any advantages in design. To be sure there is "NO HP" to ge gained by installing these pistons over OEM or Kimpex and the fact that they are forged just means that they require careful warm up and operation.

I have SPI's in my 800 doo and they have been there for atleast 800 miles. Had the cylinders off to do some work to them. The pistons looked outstanding as well as the rings.

BTW...this is a fully modded motor with twin pipes

I have SPI's in my 800 doo and they have been there for atleast 800 miles. Had the cylinders off to do some work to them. The pistons looked outstanding as well as the rings.

BTW...this is a fully modded motor with twin pipes
[/b]

Would you happen to know what a safe piston to wall clearance would be? I am rebuilding my top end and wondering if I should just change the rings. I took a feeler gauge and it was reading 10 thous on one and 12 thousand on the other. Pls advise if you could. Thanxs

flk, feeler gauge isn't the ideal way to measure but 10to12 is too loose and if you let them get worse the skirt can catch a port. Many 800's died this way, con rods and other things were often blamed but loose pistons were mostly to blame. Pick up a couple piston kits, clean up your jugs, check the ring gaps, bolt it together and ride. I'd use the spi and have had very good luck with them in the series 3 motors, even mod motors that run with your fingers crossed.

I'am running the cheapy pistons in my mod 670, I have over 1000ks so far and no problems. $57.00 compared to bombers $230.00

IMO it depends on application and price. If you are replacing all of them, then I see nothing wrong with Wiseco as long as the cylinders are correctly sized (you would be supprised how much cylinders vary frome one to another).

The Wiseco is a forged piston yes, which allows them to make a stronger piston with less material vs. a cast one, and yes, forged alum. "swells" more than cast (forged is more "dense" with a much tighter packed grain structure, thus more initial heat swelling).

The missconception comes from several things when it comes to Wiseco pistons:

1 - A forged piston grows to a bigger diamater - This is true yes, but Wiseco compensates for it in their sizing. A Wiseco piston will measure a tad smaller than a OEM. Thus while operating, they run at the correct size

2 - Prone to cold seizure - This is correct to a sense, but the nature of the forged alum is that after a couple of dozen heat cycles, the alum will "settle". The piston will swell to a bigger dia the first 6 or 7 heat cycles then it will the rest of it's life. When the proper clearances are used, you will have a superior top end IMO

Also, Wiseco uses a very high quality, VERY hard chrome ring. They typically will take 3 - 4 times as long to "seat" as a OEM ring. In my 01' 800 Doo it took nearly 500 miles for the thing to settle down and run good and for the rings to break in. This year I re-built a F7 with wisecos, and it took nearly 700 miles to break in all the way. But once they do, the life span is much much much longer than Oem (Doo oem at least)

Would you happen to know what a safe piston to wall clearance would be? I am rebuilding my top end and wondering if I should just change the rings. I took a feeler gauge and it was reading 10 thous on one and 12 thousand on the other. Pls advise if you could. Thanxs
[/b]
yah i would go with any jobber pistons i always just run the boxers i run them in everything i have two open mods i run them in both and have never had an ounce of trouble with them.... i also use them in my riding sled to no with nearly 8000k and the third season of serious baggin the balls off of it it still hold comp at 135psi i dont see any problems with the jobbers.

Anybody know what type of pistons Bill Cudney uses?

I'm guessing he doesn't manufacture his own.

Jeff

Anybody know what type of pistons Bill Cudney uses?

I'm guessing he doesn't manufacture his own.

Jeff
[/b]


They are SPI from what I have been told. They may have additional treatment

one more!

They are SPI from what I have been told. They may have additional treatment

one more!
[/b]


Thanks James.

Yes, one thing I had heard he does is glue the ring retaining pin in place.

That should alleviate some of the ring issues that some people on high-mileage sleds experience. That was one of the reasons I'm leaning towards his pistons.
I realize, glueing is something I could probably do myself, but why subject my wallet to all of that "trial & error" learning. Bill's got a great reputation. I figure I'll go with his experience.

Jeff

I just finished off the season with 2100 miles on Wiseco's. I pulled the raves the other day and took a peek at the pistons and all 3 were scuffed with the center one bad enough to start sticking the rings.
I pulled the jugs and they are all right but the pistons are junk and OEM's have been ordered like I should have in the first place. This is anothe live and learn experience so just bite the bullet and get what was made for it and be done with it!
I might as well have taken 300 bucks and flushed it. Yes I warmed it up every time, I'am very anal about this. Should have listened what most have said about Wiseco's in the first place [Seizeo's]. Guess they would work if you bored the cylinders 5-10 over and give them lots of expantion room?

I just finished off the season with 2100 miles on Wiseco's. I pulled the raves the other day and took a peek at the pistons and all 3 were scuffed with the center one bad enough to start sticking the rings.
I pulled the jugs and they are all right but the pistons are junk and OEM's have been ordered like I should have in the first place. This is anothe live and learn experience so just bite the bullet and get what was made for it and be done with it!
I might as well have taken 300 bucks and flushed it. Yes I warmed it up every time, I'am very anal about this. Should have listened what most have said about Wiseco's in the first place [Seizeo's]. Guess they would work if you bored the cylinders 5-10 over and give them lots of expantion room? [/b]

between what you just said and what idooski told me an hour ago I will not touch them.

it was my understamding that on wiseco's you needed to drill holes in the skirts for lube. because of the tight tolerence. could of sworn i read it on here.

I'm running properly sized and Swain Tech coated Wisecos on my 670 and have followed a good break in protocol with no problems to report. The so called made in Taiwan pistons aren't so bad. Anyone who's been there will notice that they have a 2 stroke society. Scooters, trikes, cars and cycles everywhere.

well I have stock yamaha pistons in my vmax 800, but just bought 4 kimpex pistons B/N in boxes on ebay for $60 canadian shipped for my second vmax 800 motor I am building.....I am going to get them coated....time will tell!

I used Wisco in my 2001 T-cat. The ring retainer pin pushed up and the ring turned around until it caught the exhaust port. The cylinder was ripped up and the top ring land was pulled off.

Take a look at the way the rings are retained on a Wiseco compared to a Suzuki piston. On the Suzuki, the pin is trapped under the noch in the ring so it cannot come out. Also the ring ends are square and not ramped like the Wisco. the ramp allowed the ring to get under the pin and push it up and allow the ring to walk. It's OEM for me.

Jeepers!!! Any of you people think that just maybe it might take a little bit of knowledge to be the tech editor of this forum? This guy knows what he's talking about or did all of you miss that? Wiseco pistons are higher quality then O.E.M. ! In everyday use they don't perform as well because thats not what they're made for! 8 second 1/4 mile cars use Wiseco pistons! 16 second 1/4 mile cars use O.E.M. !!!!!!!!!!!

One more for the SPI's. I currently run them in a mod 800 XCR that routinely sees 9000+ rpm. A little info i haven't seen in the thread. The ones you want are the SPI T-moly series, they are sold out of the SPX book by most aftermarket companys. These are Hyperutectic(high silicon content) same as OEM or better.Tolerences and weight are closer than OEM + the teflon/ceramic coating and half the price. Nothing wrong with OEM except the highly inflated price tag 150.00 for a 40.00 piston!
Also these are in no way shape or form Kimpex pistons, yes they are probably a sister company.
The Kimpex pistons are just cast alum not high silicon and they are not coated, definately not for a hot high perf engine.

Jeepers!!! Any of you people think that just maybe it might take a little bit of knowledge to be the tech editor of this forum? This guy knows what he's talking about or did all of you miss that? Wiseco pistons are higher quality then O.E.M. ! In everyday use they don't perform as well because thats not what they're made for! 8 second 1/4 mile cars use Wiseco pistons! 16 second 1/4 mile cars use O.E.M. !!!!!!!!!!!
[/b]

:lol: Ya and after that 8 second run they throw them in the junk along with the rods or sell them to a retarded fan for $20 bucks. :crazy:

I have 3 high quality slightly gouged Wiseco pistons if you want them, just pay $300.00 in shipping and you can have the best pistons on the planet.........

I know what you are saying Mike. In my 10 second street car I have a set of 30 year old TRW pistons that have seen more 7000 plus rpm pulls than most would see it two life times... I am retiring them thios year only because I am taking the BBC out to .100 over but, I am putting the same style back in. I won't buy the high priced over rated snake oil!!

Brian

Howdy!
I did not read the whole tread but this is my opinion on the pistons.

The oem pistons would be my choise for a stock trail machine because of
the lower cyliner clearence when cold and less risk of cold seizure.

But on a piped sled i love the wiceco`s! They are pretty much undestructable
and would not fall apart if detonated like most oem`s but might do if they were often not warmed up properly and skirts are eaten so much that they rattle apart.

My F8 are hot enough for take of when the entire cooling system is warm. (100 F)

Just feel the right running board, when its hot its done!

Ove

Jeepers!!! Any of you people think that just maybe it might take a little bit of knowledge to be the tech editor of this forum? This guy knows what he's talking about or did all of you miss that? Wiseco pistons are higher quality then O.E.M. ! In everyday use they don't perform as well because thats not what they're made for! 8 second 1/4 mile cars use Wiseco pistons! 16 second 1/4 mile cars use O.E.M. !!!!!!!!!!!
[/b]

IMO Wisecos are great for their purpose. They are a successful company very involved in racing. When properly installed they should be great pistons. I rode with my friend who rode a YZ 80 with a Wiseco in it and almost everytime we left he would be half way down the trail before mine was remotely warm. He did this all the time and the wiseco held up amazingly. Bike still runs strong and has well over a year of riding on it. The book recomends a rebuild way before that.

:lol: Ya and after that 8 second run they throw them in the junk along with the rods or sell them to a retarded fan for $20 bucks. :crazy:
[/b]

8 second cars don't get rebuilt every race. Many run for multiple seasons without being rebuilt. 4 second cars get rebuilt every race but, once the pistons pass a careful inspection they go back in. If they don't pass they get sold to brainless fans. The aluminum rods are so distorted they can't be reused.

The whole point was that all you have to do is warm up your sled before you take off. Afterall if o.e.m. pistons were all that, You wouldn't be replacing them.

A 2 stroke at 8000 rpms see's fire on top of that piston 4000 times per minute. A 4 stroke will only see it 2000 times (both being single cylinders). A 2 stroke lives a hard life, especially in a snowmobile, running at high rpm's all of the time. No matter what piston you use, warm it up before riding. If you go for the forged, make sure it is completely warm, thats all.
I run the SPI’s because they are inexpensive. And I will replace every other year or so. If I ran the Wiseco’s, I would do the same.
The only problem I see with the forged piston in a newer sled engine, is the Nikasil bore. You just can’t pull the old cast pistons and through in the forged. You will have to set them up for proper cold start clearances.

My experience with wiseco is you need to let the motor get warm before reaming it.Forged is the way to go.

Jeepers!!! Any of you people think that just maybe it might take a little bit of knowledge to be the tech editor of this forum? This guy knows what he's talking about or did all of you miss that? Wiseco pistons are higher quality then O.E.M. ! In everyday use they don't perform as well because thats not what they're made for! 8 second 1/4 mile cars use Wiseco pistons! 16 second 1/4 mile cars use O.E.M. !!!!!!!!!!![/b]
I have been around racing sleds as long as the tech editor, maybe longer. I run oem in my sleds period, personal preference. forged pistons are a cost if not needed, they weigh more. more weight more hp to drive them. when forging a piston the material is pressed(forged) while still molten into the mold. thus leaving a more dense piston, with more metal in it. thus the problem in a stock bore. I have a very hot 331 that builds 475 hp and it has kieth black hyperutectic pistons in it. I have another 331 with 400 that has trw forged in it. both about the same hours and the pistons are in great shape in both. basically it is personal preferece and what has work for you in the past. mainly is it setup correct. I would not use wisecos but dad swore by them.

Yeah but most OF the so called "gearheads" here are more like knuckleheads! they think a wiseco piston is the same as an OEM ......FORGED and CAST or 2 different types of pistons.....So in short I would recommend if you dont know much about forged slugs stay with oem pistons! I just wasted 60 seconds typing this as an knucklehead will post a simalar thread probably not long after this one simmers down! prey fro snow everyone


Jeepers!!! Any of you people think that just maybe it might take a little bit of knowledge to be the tech editor of this forum? This guy knows what he's talking about or did all of you miss that? Wiseco pistons are higher quality then O.E.M. ! In everyday use they don't perform as well because thats not what they're made for! 8 second 1/4 mile cars use Wiseco pistons! 16 second 1/4 mile cars use O.E.M. !!!!!!!!!!![/b]

Most forged wiseco's made for performance snowmobiles are LIGHTER than the cast oem pistons for the same model. Since we know a forging is denser and should be heavier this tells us that the wiseco's are not as strong as some would claim , and/or the modern castings of the oem pistons has come real close to a forging in density and or are made with thicker walls. When it comes to the cast vs forged (wiseco's anyway) debate in sled pistons, forget all the sbc and ricer car tech you've heard about. They are not the same pistons. Most mod sled engine builders would prefer to use a quality casting, but are often stuck using a wiseco because of size and availabilty, not because they are forged.

wiseco pistons are good quality more resistant to detonation, they have to run higher clearances than cast due to the higher thermal expansion coeficient of forged vs cast. this is a mute point on a chrome bore because it is not being resized anyway. they come properly clearanced from the factory. they are not lighter than cast as this would upset the balance factor in a sled that is only seeing a top end r&r. spi make good pistons the metalurgy and quality controll in forign countrys have jumped in leaps and bounds in the last 20 years. oem are great but some people are complaining about the single ring design. wiseco and oem are expensive therefore i use the spi , with the exception of a high compresion or nitrous motor then i use wiseco.

This hole thing needs some more details, wiseco pistons are great for racing but u will have to rebuild your motor every season from then on oem 100%

Pat

WOW !!! piston brands sure polarize you folks. Lots and lots of here-say and Myths.

Anyone have a thought about these?
http://cgi.ebay.com/ebaymotors/ws/eBayISAP...mMakeTrack=true (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=300150880655&fromMakeTrack=true)

I've read all 4 pages of this thread and am more confused than ever. I should replace my pistons as I have 4800+ miles on my 99 ZR500efi. These say "OEM quality" but I see from you guys that might not mean OEM design. As to the racing verses trail discussion, I'm definitly only a trail rider and would consider myself hard on suspensions but definitly not engines.

Also, my knowledge is not extensive on this subject but I did take a small engine repair class for fun last year. You guys keep mentioning a ring rotating and catching on the exhaust port thus destroying lots of expensive stuff. I was to understand that the rings are SUPPOSED to rotate and the crosshatch in the cylinder walls makes sure that they do rotate. (the 45 degree crosshatch asures the proper speed of rotation.) The rotation keeps a raised groove from wearing in the cylinder wall where the gap in the ring is. Am I wrong here???

I ordered 1999 efi service manual but this simple piston/ring job is scaring me more and more......

Anyone have a thought about these?
http://cgi.ebay.com/ebaymotors/ws/eBayISAP...mMakeTrack=true (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=300150880655&fromMakeTrack=true)

I've read all 4 pages of this thread and am more confused than ever. I should replace my pistons as I have 4800+ miles on my 99 ZR500efi. These say "OEM quality" but I see from you guys that might not mean OEM design. As to the racing verses trail discussion, I'm definitly only a trail rider and would consider myself hard on suspensions but definitly not engines.

Also, my knowledge is not extensive on this subject but I did take a small engine repair class for fun last year. You guys keep mentioning a ring rotating and catching on the exhaust port thus destroying lots of expensive stuff. I was to understand that the rings are SUPPOSED to rotate and the crosshatch in the cylinder walls makes sure that they do rotate. (the 45 degree crosshatch asures the proper speed of rotation.) The rotation keeps a raised groove from wearing in the cylinder wall where the gap in the ring is. Am I wrong here???

I ordered 1999 efi service manual but this simple piston/ring job is scaring me more and more......[/b]
yes, wrong. doo pistons even have a pin to keep them from rotating.

yes, wrong. doo pistons even have a pin to keep them from rotating.[/b]
some info for you. http://www.aa1car.com/library/2000/ar90058.htm http://www.hastingsmanufacturing.com/Servi...refinishing.htm (http://www.hastingsmanufacturing.com/ServiceTips/cylinder_bore_refinishing.htm)

Thanks for the info. I'll do some reading this afternoon.

I asked the guy who makes the pistons above and he says they are cast, SPI pistons (and coated if that makes a difference.)

one thing to note is we are refering to a 2 cycle with ports not a 4 cycle with valves. which you would be correct on the rotation. proper rotation would be had with the correct hatch. I just read my post from earlier and it said "doo pistons have the pin" all should have not just the doo.

A nice alternative ,if they make them for your sled, is SPI.
They are coated, skirts and tops. Measure identical, in all that I have used.
They have worked well for me and others and usually run about $75Can with rings,pins and clips.[/b]

put these spi's in mine last year, drove 1200km in three months. just checked the walls from the exhaust and no wear at all. took head off and whas was perfect on tops
Highly recommend them, plus the price is bare bones!!!!

Well there are some excellent posts up there. Just want to add my 2cents. The problem with wiseco is that the rings are usually thinner then stockers and the top piston landing is considerably thinner making the top of the piston very weak. Also I have heard that the pin which holds your rings from turning like to come loose and cause the ring to turn which eventually finds the exhaust port and pop the ring hangs up and smashes the top of the piston usually breaking the top off. As for kimpex I have never seen anyone have luck with them. The SPI's I would say is your best bet. For example, my 98 xc 600 blew up on me. So I did the same thing as you pricing pistons. I got a set of SPI's and just comparing them to the OEM's there was no difference at all the casting on the bottom side of the piston was identical and everything. But my guess is that they are OEM pistons that didn't come 100% into specs and were rejected for weight or dimensions but I never had problem. Then again I didn't keep the sled long after but have only heard good thing on them. Good luck with the Wiseco's ;)[/b]

Here is a picture of a Wiseco from the early 80's that had the ring pin come out and wreck a piston, cylinder, head, and possibly the crank. I pulled this out of my 75 340 SnoTwister just after I picked it up late December 2006. It had been sitting in a barn since it puked in 1984. I understand that this was a problem a couple of decades ago, but I haven't had any problems with any of my newer Wiseco's

[attachment=40183:twister_wiseco.jpg]

i ussualy go with wiseco on my vintage sleds. but on my XCR i went with SPI, and no problems so far.Wiseco's do expand faster but what i ussualy do with the old sleds when i freshen them up is just measure cleareance, and if all is good, i just hone the cylinder a lil bit and throw the wiseco's in. the only problem i had was on a 75 TNT 440. Put wiseco piton in, and at the end of the season the part of the piston in between the two rings broke off and shot out the exhaust. I have no idea what caused this maybe someone knows? Go with Wiseco or OEM. #### Kimpex they suck

i had been running oem's in my tcat and i had cut all the heads to spec of 78 thou. i installed some new kimpex pistons and decided to check the squish ,98 to 100 thou. if i had never cut the heads to begin with i would have had a squish band of roughly 120 thou with kimpex pistons.
other than that 200 miles and so far so good. i guess i cut the heads again

The OEM pistons for the Mach Z 1000 have been found to be in and out of tollerance. So im not sure whats going on there.

But Ive had very good luck with wesico's in the past. As long as you give engines with wesicos a little longer to warm up, they will give you great and long performance.