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Yamaha MX & Off-Road Dirt Bikes
yz85 problem and piston questions????
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[QUOTE="TCYFudge, post: 1279937, member: 77802"] Hey everybody. i need a little help with my yz85. a little bit of a long story but please bear with me. i searched my problem and couldn't find anything. anyways... my piston clearance came out to 49.5mm (i was told by my mechanic) and stock is 47.5mm. my last piston (same one in now) is a 49.5mm. after breaking it in and everything, it was seizing. that obviously means the piston was too big correct? well.. i kept that same piston because i didnt have any money and it never seized again after shaving the high spots. well just the other day i was having an unusual a problem at WOT. it was stuttering and didn't want to give it all it had. i had severe bogging problems at WOT mainly from 3rd to 6th gear. the bike would pull the front up like normal but once at a higher gear it would bog down and almost die if kept on the throttle. so i messed with jetting, mainly the main jet because i had problems at WOT. nothing seemed to help. then all the sudden the bike was dying like it never had before and killed the engine. i pulled the plug and it looked great. a nice tan to it. then i put the plug back in and tried to kick it and there's no compression. i get home and pull off the cylinder and piston and stuff. i put the piston ring in the cylinder and its looks pretty badly warped. my piston doesn't look that bad, other than the spots it was seizing before. but then i put the ring onto the piston and then the piston into the cylinder and one side had a bad gap in it where i can see light. now onto my questions. 1. do you think i should get a whole new top end or just a new ring? if you say top end, should i get a 48.5mm piston because the last 49.5mm was seizing? 2. also, do you think that would be the cause of my bogging and loss of power and no compression? p.s. i was having this problem after switching from castor 927 to yamalube 2r. I'm not sure if that has anything to do with it though. [/QUOTE]
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Yamaha MX & Off-Road Dirt Bikes
yz85 problem and piston questions????
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