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Post by cyclerod48 on Apr 6, 2021 17:26:18 GMT -5
What should the compression number be on a 1988 Yamaha Jog? Mine is reading 60 psi. Seems low but I can't find what it should be.
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Post by pinkscoot on Apr 6, 2021 18:22:05 GMT -5
If you have a good compression gauge you should be in the 120-160psi. Anything below 100psi is usually a non starter. What Gauge do you have and why are you testing the scoot?
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Post by Zino on Apr 6, 2021 19:28:52 GMT -5
At 60 psi your gauge is either wrong or your scooter doesnt run
120 plus works well
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Post by cyclerod48 on Apr 6, 2021 20:59:12 GMT -5
I was using a top of the line NAPA compression gauge. I also let the engine warm up before testing it. The engine idles fine and mid-range runs good. At wide open throttle it will run for approximately 15 -30 seconds then dies off like it is starved for gas. So far I have installed:
a new fuel cock with a new filter
installed a new carb
installed a new set of reed valves
new spark plug
Nothing has made any difference and was told it could possibly be caused by low compression.
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Post by pinkscoot on Apr 7, 2021 7:36:19 GMT -5
Are you opening the throttle all the way when you test?
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Post by geoffh on Apr 7, 2021 15:02:30 GMT -5
From the service manual std 114 min 91 both psi.
Geoff
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