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General Category => Maintenance => Topic started by: jerryXR on December 31, 2011, 05:58:20 PM

Title: Comp test + leak down test?
Post by: jerryXR on December 31, 2011, 05:58:20 PM
I have a brand new set of carbs on my bike and want to jet started
re-jetting them. I'm running pod filters and a pipe so i started tearing
her down. So this is a good time to check the valve clearance. So
what the hell lets do a leak down and comp test. The leak down was
good 2 cyls. were perfect and 2 with about 3%. The comp test ?
#1 110 #2 109 #3 115 #4 114
I think i should see higher comp #? I'm going to run to work and get
another comp gauge and retest. The valve clearance is not that far
out of line.
jerry
Title: Re: Comp test + leak down test?
Post by: jerryXR on December 31, 2011, 06:23:30 PM
Wanted to add it has 78mm pistons @ 10.25:1
thanks
Title: Re: Comp test + leak down test?
Post by: Pat Conlon on December 31, 2011, 07:34:04 PM
You are at the minimum. Q: Motor warm and throttle wide open? Common mistake not holding the throttle wfo. Gives you low readings everytime.
With oem 9.7-1 pistons, at sea level you should range from 140 to 170 psi (9.8-11.8 bars) With 10.25-1, I would guess somewhere ~180psi.

Before Randy rebuilt my engine, I was running 105-115 psi and the motor ran fine, just a bit soft on power. Ran this way for years.
Title: Re: Comp test + leak down test?
Post by: jerryXR on December 31, 2011, 09:08:18 PM
Yes warm engine throttle wide open. I went and got another gauge but
same readings. I added few drops of oil in the cyls. and bumped up about
15 to 18 psi. I have a snap on camera that i'm going to go down through
the spark plug holes and take a look. I checked my cam timing with a degree
wheel and looks good. One other thing i pulled the header and a few exh valves
look to have oil on them. I know that has nothing to do with my #s.
jerry
Title: Re: Comp test + leak down test?
Post by: Pat Conlon on December 31, 2011, 11:01:50 PM
How many miles on the engine?
Title: Re: Comp test + leak down test?
Post by: jerryXR on December 31, 2011, 11:07:15 PM
Total 29,000 miles but pistons and valve job about 1200 or 1500 miles ago.
jerry
Title: Re: Comp test + leak down test?
Post by: jerryXR on January 06, 2012, 09:16:28 PM
I found the problem the schrader valve on the gauge was
bad. Now have 175 to 180. Always good to double check
i was ready to tear down.
jerry