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1981 CB750C carb adjustments. Won’t idle lower than 1800 rpms

Just checked the compression on cylinder 1 it’s 120-125psi. Looks like I’m gonna do the top end rebuild. More than likely that’s what’s been making my carbs go crazy.

Thanks!


 
Never tear down after only one test, you need to read them all and multiple times (3-4 at the very least) as compression testing has so many errors that come with the process. If you were not holding the throttle wide open for one, the test is meaningless. Need a good hot battery and all 4 plugs removed too. I use car battery, bike one runs down too quick. Your gauge quality can even mislead you easily, and so can the relief valve on it. A push to seal gauge is worthless there, need screw in to seal only.
 
What's wrong with 120-125 psi?? I thought those were decent numbers as long as all 4 cylinders reading roughly the same
 
It's some 50 psi off spec. Some of course are happy with a 750 that makes the power of a 500. Beyond that 120 psi is getting low enough the plugs will go bad quick due to not burning hot enough to keep really clean. They begin to foul very quickly at 100, which is considered junk level and time to retire the engine. Why missing shows up as an issue that low. Plugs get darker and darker as the compression drops.
 
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