Leakdown test not useful. Engine keeps turning over. What to do?

[coop63]

Attempted a leak down test, but every time i connected to the compressed air the piston would move and take me off TDC, this opens the exhaust valve and air flows out. Tried everything i could to keep the engine from turning to no avail. How do you get anything useful diagnostically when the piston won't stay at TDC?

[grayracer513]

The engine has to be held at just past TDC, or the timing chain disconnected for the test.

[marv02]

Put the bike in gear and secure the rear wheel from spinning.