well as some of you may remember my bike was running bad once it had heated up (missing, just running lousy) and i managed to find that most cylinders had at least one leaky exhaust valve, would this be enough to cause low compression? and for it to run bad? also i measured the end gap on the rings, and they were .1 mm out of what i could find as spec (top ring from memory was like .2-.3 and 2nd was .25-.35? anyway they were both .1mm differnt is this likely to cause a major loss of compression or only slight? i noticed the manual said .8mm was the max or something, i didnt quite understand what it meant, any help? thanks guys oh by the way, since i had the bike apart i figured it was a good oppurtunity to port and polish the head as well as clean everything out properly etc, ill keep you posted!
The specs for the gap of the rings are .15-.35 mm for the top and 2nd rings For the oil control rings it's .2-.7 mm. And I don't see where you got .8 from?
yeah i was working off an english translation and it was a bit obscure, in that case it sounds as though the rings arent toooo bad?
Ooops, I made a mistake, i said the upper limit was .35 mm but it's .30 <!-- s --><img src="{SMILIES_PATH}/icon_redface.gif" alt="" title="Embarassed" /><!-- s --> So your top rings are in spec and are fine, but the 2nd rings are a bit out by up to .05 mm. I can't say exactly how much effect that will have with oil coming through... I just don't know. Have you checked the oil control rings? I heard from somewhere (might've been a mechanic) that the oil control rings are more prone to go before the other two top rings.. I think that was it <!-- s:rofl: --><img src="{SMILIES_PATH}/icon_razz.gif" alt=":rofl:" title="Rofl" /><!-- s:rofl: -->
yeah, i didnt check the gaps on the oil control rings, my local yamaha dealer wanted 400 bucks for the rings, so i decided the old ones will have to do! after lapping the exhaust valves i realised just how bad they were, very pitted, and there was alot of carbon behind them, so im hoping ive found my compression problem. putting it back together in the next couple of days, are there any worthwhile performance enhancements i can do while its apart?
I haven't personally done any performance enhancing mods and I"m not sure if there are any that would make it that much better.... Unless you turboed it but that's just silly <!-- s:lol: --><img src="{SMILIES_PATH}/icon_lol.gif" alt=":lol:" title="Laughing" /><!-- s:lol: -->
Swap the front sprocket for a 15-toother. That's about the only worth while mod you can do on your little baby that's actually going to make more than 3/5th's of a bee's 'john thomas' difference.
I was at WSID on a bike night and they matched up two CBR250RR (one turbo, one not). For all intensive purposes, they ran the same time. (non turbo won one of the races too) <!-- s:lol: --><img src="{SMILIES_PATH}/icon_lol.gif" alt=":lol:" title="Laughing" /><!-- s:lol: --> The turbo looked fully sik if ya get my drift, oops! I mean inference.
