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Will.A.R.

low rpm under load random rattle, piston pin galling

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2004 yz450f. Been noticing a low rpm, under load kind of random rattlely almost preignitiony/ pingy sounds coming from the what sounded like the piston area left side (piston slapping maybe). Randomly and not all together rhythmic. I've done nothing to this bike other than basic maintenance in the year I've had it. runs great, pulls hard just started noticing the above. Pulled the top end apart and everything looks tip top. Piston Skirt/ cylinder clearance is in spec, crank bearings feel good, rod in play well within spec, timing chain has no binding links and so on and so on. What I did find was galling in the wrist pin to piston surface. I can definitely feel in the piston the roughness the wrist pin itself feels good. Now from my other experience wrist pin galling with no other symptoms(noise aside) is typically from assembly and start up dry or someone wringing it out while cold. I do not know the history of builds on this bike other than there is no notable wear on anything other than the wrist pin (piston side). I'm wanting theories on the wrist pin and well as possible noise causes. Could it just be bad gas?(premium fresh from the pump however). I'm going to do a top end while its apart and replace the timing chain and clutch, just wanting some ideas and whether the wrist pin issue could be an oiling issue in the making. Opinions/ criticism appreciated.

Edited by Will.A.R.

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