Small Engine Leak Down Test vs Compression Test Results - Honda CT70 Dax Z50 Mini Trail Monkey

[@donreed1133]

Thanks very much! I was having the same issue with the Harbor Freight compression tester on small bore motorcycle engines! Thanks again.

[@zachsiebers5742]

Thanks for the video. I used the CT90 blog when redoing the engine on my 69 CT90.

[@1stGenCRXs]

Great explanation. I wish mine had that much compression. My Z50 K3 has an amazing 45 psi. You have to love a Honda motor because it still runs!

[@VintageHondaMinis]

CSPCRX - Perfect example of an impossible situation based on compression gauge and small bore. Your engine would at least be above 100 psi in the real world for it to run.

[@CracowGo]

Hey that's weird, we rebuilt my honda lead80 engine with a new cylinder and piston and the compression is the same as yours....120, to make it even funnier it was the same on the previous cylinder...Can't get beyond 120, I have the same gauge as you. Cheers!

[@cpF01]

Hi. For a compression test, I thought you were supposed to test at operating temperature. I'd love to have seen the rating when warm. Thanks for posting.

[@VintageHondaMinis]

Not all engines are running engines.

[@johnoconnor5581]

I’ve experienced the exact same issue using a compression tester with a long rubber hose on small displacement engines. Eventually I cobbled together the correct air fittings to eliminate the rubber hose and have the compression tester sit right up by the spark plug hole and the psi readings increased. Still, I’ve compression tested engines that seem to run fine and never see the 157psi to 180psi the Honda manual suggests is normal for a healthy engine.

[@VintageHondaMinis]

John - Yes I have read about fixes or workarounds, for example moving the check valve to the beginning of hose among other things. Glad you are aware of this. Just wanted to get the word out b/c it can confuse someone in regards to health of the engine and cause misdiagnosis.

[@paulskinner7169]

My manual says the motor should be at operating temp before a compression test.

[@marcussmith948]

You don't know what your doing. You have to push the bike in gear forat least 20 rpm.

[@VintageHondaMinis]

I do know what I'm doing and pushing bike is not a requirement. Honda manual even states kickstart method as their way of obtaining reading - But I will try your method in the future Thanks