How many miles on your aftermarket pistons in CFI-2 engine?

[Murph]

Just like the title says, "how many miles on your aftermarket piston kit, or fix kit, or long rod kit, etc?"

Anybody put some miles on a kit yet and pull the motor back apart and check their wear yet? IndyDan, PMS, RKT, PAR, Wiseco, etc....

Really curious to separate the fact from fiction on the aftermarket parts, also curious to see real world wear versus aftermarket manufacturer claims.

Thanks,
Murph

 

[beamslayer]

I think you will be seeing results by the end of this yr on all the different kits . I know the pms has been around the longest and I got to ride a dragon last yr with the kit installed it ran rather well .
I would imagine with all the internet hype it is going to take awhile to see which kit performs the best' it may take 2 yrs to really tell . If peeps are seeing more than 2500 miles with out failure with this kits .

 

[Murph]

I've seen 2500,2000,1500 miles without failure with stock Polaris pistons on our three sleds.

What I'm looking for is aftermarket piston integrity after this many miles, are they still serviceable(probably not)?

If past their useful life, did they at least stay closer to their original spec, thereby continuing to perform better, longer?

I'm not sure when WE as consumers became so demanding and, at times, UNREALISTIC.

Honda-- who I think most will agree is a VERY respected engine builder-- calls for the replacement of pistons after 15 hours of use IN A FOUR STROKE in their CRF150, 250, 450. 15 HOURS-- and we as snowmobilers are bitching about piston replacement of a TWO STROKE at 1000 miles, 2000 miles, he[[ one guy was disappointed that he couldn't get 4000 miles out of a "$11,000" machine.


I'm not unrealistic. I'm ok with preventative maintenance. I'm ok with replacing a top end every season. I'm just trying to avoid a catastrophic failure of a components because I was TOO LAZY to pull out pistons before they degraded so badly that they beat the cylinders out of round.

To be perfectly clear, this is not an indictment of anyone else here on SnoWest-- or their perceptions, opinions of what piston life SHOULD be.

I do not want this to degrade into another "Polaris can't build an engine" bash fest-- we have enough of those threads already.

I also don't want this thread to turn into a "the kit I bought is great, all other kits are junk" or "the kit I produce solves all the problems because I have all the answers and every other kit producer is an idiot".

Too much to ask? I hope not.

I hope this thread stays alive-- and ON TOPIC-- with mileage reports of the various kits, and OBSERVATIONS of their respective performance at 0 miles, 500 miles, etc. It would be great to follow up with top end tear downs after mileage on the kits to report piston dimension changes, and cylinder changes.

Way back when, this is what SnoWest was all about. Sharing info and knowledge. Lets hope we can do that here.

 

[skibreeze]

I've seen 2500,2000,1500 miles without failure with stock Polaris pistons on our three sleds.

What I'm looking for is aftermarket piston integrity after this many miles, are they still serviceable(probably not)?

If past their useful life, did they at least stay closer to their original spec, thereby continuing to perform better, longer?

So what were the specs on those 3 sets of pistons? Failure and out of spec are completely different definitions of reliablity.

 

[Flange509]

I put in a set of RKtec's pistons. Had 1500 plus miles on originals and dont think they looked bad but the rings had a ton of blowby and were flaking in spots, cant wait to see how it runs just need snow.

 

[jdw1]

Subscribing, i would like to know the answers as well!

Yes, i think you are correct, we will not know the answers or anything for a year.

 

[Trenchmaster]

Hopefully this thread can stay on course. If a guy can add some engine performance and reliability to this machine for a reasonable price, a lot of people will be happy.

 

[PaulAnd]

2010 assault CFi4 with Rktek pro drop in piston and head kit aprox. 350 miles

 

[philsummers21]

Honda-- who I think most will agree is a VERY respected engine builder-- calls for the replacement of pistons after 15 hours of use IN A FOUR STROKE in their CRF150, 250, 450. 15 HOURS

Not sure where you got this info but Ill call BS on this. If this were true we would be changing pistions every weekend. Hell on my apex i think they recommended a VALVE adjustment at 10000 miles.

 

[LukerZ]

I believe on my 04 yfz 450 yamaha called for a new top end every 50hrs

 

[Murph]

Not sure where you got this info but Ill call BS on this. If this were true we would be changing pistions every weekend. Hell on my apex i think they recommended a VALVE adjustment at 10000 miles.

Phil, here is the photo attached out of the Honda CRF250R manual. If you look at pistons it says REPLACE every 6 races or 15 hours.

You may be correct on the Apex valve interval. The original Yamaha 5 valve per cylinder 1000cc bikes called for valve adjustment intervals at 26,000 miles. Ducati 851 Superbike of the same era required valve adjustments at 1,800 miles.

I have now taken us way off topic but it was only to validate my statement and assure people who do not know me that I do not disseminate BS.

 

[Murph]

So what were the specs on those 3 sets of pistons? Failure and out of spec are completely different definitions of reliablity.

Totally agree with you on the difference between out of spec (performance degradation) and outright failure. Neither is something that I want to ride. It is strange to me that even Polaris does not put a duty cycle or lifespan on a consumable part like pistons.

I still need to measure bore and pistons on 2011 with 2500 miles. The only one I've torn down so far. When I measure those I will post. Mine look ok other than excessive blowby. Rings don't look flaky. Curious how good the original measurements were.

With this thread I'm not trying to defend Polaris build quality. I'm curious about the performance and reliability of the aftermarket alternatives. Like many, I have four year warranties on all three sleds and am currently unwilling to risk voiding those warranties.

Hoping the data we receive on this thread will convince me that the aftermarket kits are superior in performance ( my current assumption now) and reliability. The reliability and life cycle of the aftermarket kits are the only unknowns at this point.

 

[philsummers21]

Remind me to never buy another honda

 

[backcountryislife]

one guy was disappointed that he couldn't get 4000 miles out of a "$11,000" machine.

Replacing pistons is easy & cheap. If I knew I could buy a pro, and by replacing the pistons every 800 miles I would be safe I'd already have one.

It isn't expecting 4k from pistons, it's expecting 4k from the sled/ motor in general. Pistons are like oil in a 4 stroke (actually, I replace pistons more than oil.. nevermind)

 

[Murph]

Remind me to never buy another honda

^^^^^
Yamaha service manual calls for piston replacement every 5 races (Honda was 6 races). Rings replaced every three races.


That is sort of my point. We need to pay to play. If I don't want to replace top ends on my Polaris I have a choice-- a Yamaha-- been there, I had a Nytro. So I know that I need to do top ends on a two stroke and I want to find out which aftermarket kit has the best performance/ longevity.

That is the goal of this post.

 

[gunnerthesnowman]

Just like the title says, "how many miles on your aftermarket piston kit, or fix kit, or long rod kit, etc?"

Anybody put some miles on a kit yet and pull the motor back apart and check their wear yet? IndyDan, PMS, RKT, PAR, Wiseco, etc....

Really curious to separate the fact from fiction on the aftermarket parts, also curious to see real world wear versus aftermarket manufacturer claims.

Thanks,
Murph

I hope this does not turn into a VENDOR war by me posting this and in fact i would like to see all VENDORS not reply to this because most have all ready had there say and have there OPINION on why there kit is the best , but this post is asking for CONSUMERS feed back.

I have a 2012 pro , 600mile and the piston to cylinder clearances are 8 th, in my books this is worn out , from what i have read Polaris made this engine this way so they could run it leaner in the mid to top end to meet the admissions # with out seizing the motor . Ok then there is the issue of them using a small block with short rods to make a 800cc motor( rods and piston to short for the piston bore size )
OK with saying this , what i do not understand is , if Polaris was having this seizing problem with cast piston with running it lean to meet admission# , how are some of these piston kits( forged pistons) tightening up this clearance problem and not changing the fueling.( fuel box )
Also if there is a piston to cylinder side load problem because of the rod ratio problem , how is using a shorter piston making this any better.

1) -so , yes the piston clearance issue has to be fixed , but in doing so , would,nt you have to address the fuel mapping as well
2) - yes , making the piston to fix tighter would help the piston side load issue , but so would making the piston longer
3) - if , i am going to spend my money to fix Polaris FU!K up , i would like to get some preformance gain from the kit i buy , better port timing , but if you do this by making the piston shorter then the stock one , is,nt this making the piston side loading worse then it is in a stock motor
4) - then there is the forged piston // cast piston thing , a lot of the reading i have done says that a cast piston is better in a two stroke motor

Is all this bull Sh!t

 

[Murph]

VENDORS.... have all ready had there say and have there OPINION on why there kit is the best , this post is asking for CONSUMERS feed back.

^^^^^
Good theme for the entire thread, and what I was originally looking for.

Real world testing, observation, by CONSUMERS AFTER MILEAGE -- not just after someone pulled the trigger and spent the money. The more info the better, pre installation measurements, after mileage measurements, clearances, etc.

The goal is trying to keep the thread to empirical data versus, marketing bias, brand bias, ranting, or bashing....

 

[skibreeze]

Gunner, my understanding with the RK Tek pistons is that the clearances aren't any tighter than the stock pistons. They are supposed to keep the original dimensions better unlike the stock pistons. I am installing RK Tek kits in both of my sleds and documenting both motors at teardown and rebuild. One is a new motor and the other will have a renick'd cylinder since the other cracked at 2,000 miles.

New '12 pistons

New RK Tek pistons

 

[skibreeze]

Boston Racing weighed the pistons, so the lighter weight part is very true. This alone could have an affect on performance and durability. I know that the stock pistons are at the outer limit of clearance new and collapse from there.

 

[assault11]

Got 3500 miles on my stock pistons. And they sti look great. I think stock is just fine. Stock runs great, everything else is a headache