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hardrock785
XS650 Addict
did you use the athena green head gasket? thay are a lil thicker and that would lower the compression
rebel542
Old Timer
What kind of numbers are you guys looking for?
Paulrxs650
XS650 Enthusiast
150 is pretty good
Brian902
XS650 Junkie
150 is a great number for these engines and even more important is that both are within 5-10% of each other.
Now save that compression tester and remember to use it each time you re-check.
That way you get more consistent readings using the same gauge and accurately test whether it's getting weak or not.
The biggest thing that can give you false readings is excessive carbon on the piston. Everything else gives you less, leaking rings/valves/gaskets.
Look in the plug hole for signs of carbon and if relatively clean you are good to go.
My guess, Your Fine.
Now save that compression tester and remember to use it each time you re-check.
That way you get more consistent readings using the same gauge and accurately test whether it's getting weak or not.
The biggest thing that can give you false readings is excessive carbon on the piston. Everything else gives you less, leaking rings/valves/gaskets.
Look in the plug hole for signs of carbon and if relatively clean you are good to go.
My guess, Your Fine.
I am happy with anything over about 135. I second the depends on the compression tester. AND both cylinders close. And even if one shows low: Do all your maintenance and check again later. A bit of carbon on a valve seat (common on bikes that haven't run for a long time or that had "issues" before they were forgotten at the back of the shed) run it for a while. If it isn't using much oil and runs decent don't worry.
I have put 2000 miles untouched on an engine that had 0 on one side when I dragged it out of the barn. See gggary's meatball mechanic thread....
I have put 2000 miles untouched on an engine that had 0 on one side when I dragged it out of the barn. See gggary's meatball mechanic thread....
Scrambled
Motorcycle Man
*What was stock spec compression ? (* too lazy to go get manual )
1970 through 1977 the manual says 145 psi at 500 rpm (ie electric start)
The j-k manual says;
run engine 2-3 minutes both plugs out throttle held wide open, fully charged battery, e-start till the compression stops raising.
At sea level
156 standard
128 minimum
171 maximum.
For what it's worth I can beat e-start numbers by a few PSI kicking it over.
The j-k manual says;
run engine 2-3 minutes both plugs out throttle held wide open, fully charged battery, e-start till the compression stops raising.
At sea level
156 standard
128 minimum
171 maximum.
For what it's worth I can beat e-start numbers by a few PSI kicking it over.
Brian902
XS650 Junkie
Be careful what you say or people will be too lazy to answer your questions.
