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Thanks guys!!!

i agree with the comment edits on my post. 40 to 1 synthetic is the only way to go. and yes, US Chrome cyls are replated back to stock sizes with material that is likely the best in the world.

i figured with the questions Kranjack19 is asking. its better a good skilled buddy of his or a good shop would be best for the rebuild. he deserves to have a great final product where he can just pin it happily for 30 hrs.

lastly, i expect his compression gauge is correct as 90 psi matches the look of the piston. there is no way this motor will ever produce more than 140 psi with a stock head right?... so the other guys gauge is wrong.
 

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Dirt tracker
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3,761 Posts
Nah! 90psi would run like a pig and would likely not be a one kick starter. I trust the higher number. Don't fuss over a few bitty scratches on exhaust side of piston. I have seen many new bikes with very low hours with similar wear/scratches. It always looks worse through the port because port edge is sometimes rough from original manufacture or loose carbon or debris. Small scratches on skirt wont hurt. They can help channel oil to hot cylinder wall. Old school porters would deliberately relieve cylinder wall with a burr and drill lube holes in piston skirt there to improve lubrication. Ring stroke area is where she's doing business. Piston skirt is deceptive because you see dark area and assume cylinder is badly scored. Scoring by ring area is a problem. Cylinder composite is super hard and piston is soft. Your carbonized oil cokes up and burns in scratches and looks much worse than it is. Compression and cylinder leakage will tell you when to start planning top end job. No rush here. Feed it 40-1 or 32-1 and let er rip. Study some recent reviews of your cylinder replate companies before you send yours out. I only recommend one outfit now due to recent experiences. Powerseal is my preferred cylinder guy
 

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yeah i was questioning the first kick part as that sounds great. just wanting to stay on the safe side and not advise running it in case it only blows up. but that's what's great about forums right?! we get experience and opinions from various angles... and that's a good thing.

the powerseal shop looks great. i'll use them for bikes. for snowmobiles US Chrome has a huge stock for exchange. and they have proven they have a better finish than the stock Polaris cyls on the infamous 800 twin 2 stroke that likes to break skirts. using US Chrome on that sled is one of the fixes for the issue.

i take your point about some skirt scuffing being ok, and yes some big bores run a decompression groove. but again on my rigs i never see it, even after hundreds of hours (in the case of a bigger bore woods bike). so scoring should not be considered normal.
 
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