DtMitch Posted May 13, 2015 Share Posted May 13, 2015 hi there guys im wondering if anyone could give me any advice on what to do my bike has an annoying rattling noise which seems to be coming from the top end. it had a +1.0mm rebore just under a year ago by a previous owner and was fitted with a wossner piston, which has always slapped from cold. i have taken the head off and attempted to measure the bore and got 56.97mm as my biggest reading but im guessing it is 57mm, bore looks nice and clean. but i had no feeler gauges to hand at the time. bike starts first kick every time without fail and pulls well through all gears anyway back to the noise. on start up the piston slaps is the prominent noise from the engine, however there is a rattle which seems seperate.to the slapping in the background. the rattle is there at tickover, not so much on acceleration but very distinctive on de-acceleration however is seems seperate from the engine speed. its really annoying and difficult to explain. Any advice would be appreciated, thanks Link to comment Share on other sites More sharing options...
blackhat250 Posted May 13, 2015 Share Posted May 13, 2015 Aye mitch " Small end roller bearing, whip the head off, twist the piston back and forth [ clockwise+-anti,] play should be minimal, I canna see it being piston slap ,as its been bored, the rings can be noisy , ask airhead, his rattled like a snake, sumone had widened the exhaust port- and rings were snagging,,, Link to comment Share on other sites More sharing options...
DtMitch Posted May 14, 2015 Author Share Posted May 14, 2015 ok ive just ordered a new bearing and gaskets which will hopefully be here tomorrow, if so ill strip the top end down on saturday and ill post my findings on here. i just really want the rattling gone as im selling in a couple months and it really lets the bike down Link to comment Share on other sites More sharing options...
DtMitch Posted May 16, 2015 Author Share Posted May 16, 2015 ok.so ive stripped the top.end down and cant really find anything wrong with the little bearing so it must be the piston and bore. im replacing the bearing anyway and ill let you know how it goes. a create a problem for myselft tho, trying to be clever i thought i could remove the whole top.end as one, and forgot to drain the coolant. so now my crankcase has coolant in it Link to comment Share on other sites More sharing options...
DtMitch Posted May 16, 2015 Author Share Posted May 16, 2015 ok so top of piston measures 56.40mm and the bore measures 56.98 is this right or does it seem too small? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted May 16, 2015 Moderator Share Posted May 16, 2015 the top of the piston always measures less than the bottom ., because the top gets hottest and it's to allow for expansion. To check piston you should measure it at the bottom and compare to Yamaha specifications in the workshop manual Link to comment Share on other sites More sharing options...
DtMitch Posted May 16, 2015 Author Share Posted May 16, 2015 ooohh.well its back together now and sounds exactly the same Link to comment Share on other sites More sharing options...
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