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CB750F SS, 1980

Ricebiker

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The bike was diagnosed with low compression today. Too low. I got 120 psi on the two outer cylinders and when I squirted oil in there and retested it went up dramatically, leads me to rings/cylinder compression. Really strange because the bike runs well. Doesn't burn oil, etc. It just has this stall above 3/4 throttle that I thought might be carbs. Felt like a carb problem. I don't think I'm going to fix it, just wouldn't be worth the money. I'd never get it back. The riding position is very prone, so my wrists can't really take it for long periods. Not my forever bike, ya know?! 20151118_142547.jpg
 
Everybody always thinks it's the carbs.............just like everybody blaming the rings. Unless bike has been abused or 30K+ miles on it then the rings are likely OK, you can easily get oil into exhaust seats to run the squeeze readings up and why so many of these change hands when all they needed was a good valve setting episode.

If still too rich you have created that higher rpm brick wall so many do too with those CVs. The slides absolutely will NOT open with too rich, even a little kills the crap out of them. At 120 psi you should at least be able to hit 7500-8000 rpm. BTDT.
 
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Then you're there possibly. On taking many of them apart I find the ring wear to have gone all the way across the width of the rings signifying they are pretty much done. At least one ring (2nd IIRC) is a reverse torsional twist one that wears beginning on one edge only, then slowly makes its' way across the ring width, when it does the ring is considered worn out. That usually shows up around 35K+ or so, about the same time that the tensioners begin to break from the rubber being hard enough to crack and fall off, at least here in Texas. The heat just kills that rubber here. like with all my car tires. I never buy max mileage tires, the cars will all suncrack the tires long before you get the mileage, I alternate cars too much.
 
I've had this bike since '95
Maybe it's time for someone else to enjoy it. Someone that can rebuild motors. But, I am shopping for a engine mechanic in the area.
 
I'm ALWAYS trying to be helpful, it's just that many don't want to hear what they don't like.

Add to that I tend to be pretty terse about things, yes, it's a flaw.

Luck................
 
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