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smoking issue after cosworth piston install.

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think i might have an issue after installing a cosworth piston, as on start up it smokes blue qiute a bit and after about 3 mins it seems to get better. i installed it the dry way. and the rings where properly spaced. has anybody else tryed these pistons as they are new over here in the uk. my bike is a 08 with 40hrs on it and the barrell still looks like new inside

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Cosworth makes good stuff, what do you mean by the dry way exactly? ring end gaps are spaced apart, ring end gap correct? made sure you didnt overlap the oil expander ring?

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i installed the piston with no oil the same as most people do of thumpertalk all ring end gaps was spaced as manual describes.

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Was it smoking before the rebuild? could a valve stem oil seal have gone? oir could the piston just need bedding in?

Does it smoke on the stand or is it really bad whilst riding?

Ring the piston supplier and tell them you have problems and see what they advise.

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white smoke is oil. Sounds like you didn't install something correctly.

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most pepole dont asemble dry just some from thumper talk .may be its the small metal particles that have been torn loose from your rings and embedded into your piston causing more microscopic scratches and destroying your ring seal even more all because of zero lubrication.or you could have just overlaped your ol scaper.

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it didnt smoke before the rebuild. im going to strip it again this week to check everything is installed correctly. from what ive read on here the dry rebuild is the way to go. did this last time with a genuine piston kit and all was fine.

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it didnt smoke before the rebuild. im going to strip it again this week to check everything is installed correctly. from what ive read on here the dry rebuild is the way to go. did this last time with a genuine piston kit and all was fine.

Ron is right, dry rebuilds are a no, no contrary to some of the myths you read on here. My guess is you had the ring over the oil scraper pull out and over the scraper ring. It is extremely easy to have happen when you are putting your cylinder on.

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One more thing. As an assembly lube I use a mixture of %50 STP oil treatment and %50 of whatever engine oil your going to run in your bike. I'm an aircraft mechanic by trade and this is what is used in the A/C world to assemble engines. It makes it very sticky and will stay in place till the engine is running. It works great.

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Clean cyl/piston real good, spray a thin layer of wd-40 on the cyl walls, using ring seat powder, rub it into the cylinder wall and install dry piston/rings (oil wrist pin of course) thats the correct way to rebuild the motor "dry"

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i will find out tomorow after ive pulled it apart. thanks for the info though

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so if one of the oil rings did get folded over do i need to replace the rings or will they be ok?

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One more thing. As an assembly lube I use a mixture of %50 STP oil treatment and %50 of whatever engine oil your going to run in your bike. I'm an aircraft mechanic by trade and this is what is used in the A/C world to assemble engines. It makes it very sticky and will stay in place till the engine is running. It works great.

My father is an aircraft mechanic he was featured in EAA magazine this spring for developing the electric starter kit for antique aircraft and getting it ffa aproved

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My father is an aircraft mechanic he was featured in EAA magazine this spring for developing the electric starter kit for antique aircraft and getting it ffa aproved

that's awesome. Way back in 1980 my dad bought a cessna 172. We owned it for 6 or 7 years. then sold it to a buddy of his whom later sold it to a broker. At about that same time, Cessna started building small A/C again so AOPA magazine wanted to buy an older 172 and completely refurbish it and see what the cost was compared to the new ones that were absurdly priced. Well needless to say they bought our old 172 (1978 model). It was in their mag. every month for about six months with pictures of the progress. It was really neat.

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right ive pulled the top end off and all looks good, rings wasnt overlapped and all ring end gaps was where they was suppossed to be, no damage anywhere. one thing i did notice when i put the cylinder back on was that if i pushed the top of the piston side to side that the piston rocked in the cylinder, is this normal? also if its rich on the jetting it would puff black smoke yeah?

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Ron is right, dry rebuilds are a no, no contrary to some of the myths you read on here. My guess is you had the ring over the oil scraper pull out and over the scraper ring. It is extremely easy to have happen when you are putting your cylinder on.

+1

I've never heard of a dry rebuild?

I don't ever use assembly grease, but I always COAT every component in oil, lots and lots of oil

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+1

I've never heard of a dry rebuild?

I don't ever use assembly grease, but I always COAT every component in oil, lots and lots of oil

i believe ron uses ring seat powder on the cylinder wall for break in (dry lubrication) and coats the skirts in oil..

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right ive pulled the top end off and all looks good, rings wasnt overlapped and all ring end gaps was where they was suppossed to be, no damage anywhere. one thing i did notice when i put the cylinder back on was that if i pushed the top of the piston side to side that the piston rocked in the cylinder, is this normal? also if its rich on the jetting it would puff black smoke yeah?

blue smoke = oil

white smoke = water

black smoke = fuel

I can't coment on the piston rock as i've not rebuilt a crf before, but i've never had it bad on a road race bike.

Did you check it for rock when rebuilding? it shouldn't go side to side across the little end bearing if that makes sense?

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Piston rock is bad news. If youre jug is good it probably means there's something wrong with the piston, usually too small and the wrong diameter. Piston rock ruins jugs and sometimes if its bad enough can have a piston end up turned 90 degrees in the jug

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