coyote5122

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Ive recently heard about people that pinch the sleeves that have lost compression but still have life in them ? I dont mean to sound like a noob but where and who does this and are there better candidates that should be pinched over others ? I have 3 piston sleeve sets from a axial .32 and SF racers edge .32 that have been replaced and they still have some pinch at the top and i was wondering if It would be cheaper to get em pinched versus ordering new ? How much compression does this process restore ? If any one has links , Ideas or answers please help a guy out .
Thanks for your time , ideas and comments .
coyote5122

Motorboy

It is normal the piston are tight in the sleeve at top of dead center when the engine are cold. It is neccesary to have the sleeve tapered to keep compression under starting. When the engine are running and the sleeve are expanded from taper to straight in same time with the piston are a bit little expanded.

See at the link her: http://www.mecoa.com/faq/abc/abc.htm

Also nothing to be worried.

But if the engine has peeled nickel layer in the bore, there are loss of compression. (most common in some OS engines).

coyote5122

My Feedback: (25)

thanks for the response and the link I understand how everyting works just wanted to know about pinching and reconditiong services . So far Ive found one at www.rayaracing.com 20 bucks for a pinch and recon . compered to 70 to 125 bucks for p/s set i think ill be sending one off to him and see how it does . his website looks pretty good .

Sport_Pilot

What if it has no pinch at all? Some of my best engines have no pinch and have very good compression, they last a long part of their life that way. If it runs good run it, don'w worry about a good running engine no matter what someone else says. 95% of everything you hear is BS.

But if you are still worried, then check the engine by rotating it by hand not with the starter, you should feel a slight resistance at or near TDC. It won't be enough to feel by pulling the starter cord of a well run engine, but it most likely there. Even if it's not there, just put some castor in your fuel and run it, if if runs good faagadabodit!

coyote5122

My Feedback: (25)

the P/S's in question have about 4 gallons on each of them and Yes they still run but they idle erratically at times and the overall performance isnt there any more . they have less then a a millimeter or two before reaching hte top of the sleeve . I'm not a serious racer but the gang that runs up here are pretty serious and I like to keep my equipment well maintained I can normally tell a difference at about 3.5 gallons and thats when I know its getting close to replacement my engines always run around 230 to 240 and hold a great tune . Ive just grown tired of the cost of replacement parts . and as far as running great with no pinch I had a axial .28 frag the con rod after 4.5 gallons and I applied the same thoughts to it " its running fine but not great so ill just keep running it for a few more tanks to finish out the day . on the final race 4 th lap BLEWIE no more con rod now I have a scratched up .28 with bad bearings . and for the cost of replacement parts i'd be better off buying new .
thanks
coyote5122

Motorboy

Bad compression will give idle erratically..

But before you are replacing the sleeve/piston set cause by erratically idle, check this: http://www.osengines.com/faq/faq-q729.html

coyote5122

My Feedback: (25)

Thanks motor boy Ive never had a problem with proper plug selection or any other items in that link i have been running nitro for a few years now and like to think that I'm pretty good at tuning and carb adjustments . I replace the gaskets on the exhaust every gallon wether they need it or not and a few of the guys here have had me tune their cars I was simply wondering about the pinching to get the compression back . I usually run the blue sharpie test on em and find that they lose a good amount of power right around 3 gallons . But i have a sirio .12 evo 2 in a TC3 that has over 5 gallons on it and still runs like the day I got it . I guess its true you get the quality you pay for .
thanks again for the ideas
coyote5122

proptop

My Feedback: (8)

Coyote...FWIW, rayaracing is the one I've seen recommended the most often in the car engines forum...he gets good reviews/feedback from the guys who've used his services.