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compression tester

vibrac

Well Known and Active Forum Website User
VOC Member
Always thought these guages were a bit car orentated I suppose if I wanted to check the condition of the machine my right leg would tell me or I would whip the top off and look however I have bought myself one and wonder what sort of figures I should see for say 8:1 9:1 10:1 in good condition? or is there a chart somewhere for all ICE engines?
 

greg brillus

Well Known and Active Forum Website User
VOC Member
Tim, remember to hold the throttle wide open for an accurate result, and at least 3 to 4 compression cycles per test. I would expect around 150 psi to be a good start on a healthy engine. Cheers.......Greg.
 

Kansas Bad Man

Well Known and Active Forum Website User
Non-VOC Member
I use the compression tester on the liner. First when testing make sure the throttle is at full open, next spin the engine with rollers or starter. My liner with 6 to 1
pistons will give me a reading of 115 to 120 pounds, remember the liner is blown , if your bike is in good nick and your cams are mk 2s you should have a reading of not less then 150 lbs to 170 lbs probably 155 to 165 will be good. Less then 150 lbs, you want more compression with high test fuel.

Best Max
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
Usually used by car guys to compare all cylinders, should be no more than 10% difference. There are no hard + fast rules for compression ratio to pressures achieved. The cams make one major variable. The same motor with,say 9-1 ,will make higher pressure with touring cams, than with long duration "racing" ones. There is a saying "in the trade" anything over 100 lbs an it will be capable of running. Your results will be on the low side if only using a kickstarter , but they should be repeatable. Make a test, record the results, get to know what to expect, if it is lower than usual it is pointing towards problems.
 

Monkeypants

Well Known and Active Forum Website User
VOC Member
I have had a compression tester for years and recently purchased a leakdown tester. I prefer it to the compression tester. It gives more consistent readings, doesn't require kicking to the point of hyperventilation and will tell you more about the condition of the engine.

Glen
 
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