I have searched and really haven’t found good instructions on the procedure for doing a leak down test. I have read that it is almost impossible to stop the motor from rolling over from tdc when air is applied to the cylinder. Any tips, stories of experience, or guidance would be much appreciated on the process. As well as what is considered “acceptable” blow by while performing the test.
I searched for some time. I finally found a crank “lock” tool that holds the crankshaft near or at TDC (power stroke, with chamfer/groove facing towards bottom left bolt hole if viewed from the side of the engine) with two bolts. It works well.
I bought it from Innovative Karting in Phoenix.
If you can keep above 3.5-4% leak your engine is quite healthy. Anything more than that, and you likely are losing a bit.
Head gaskets often tear between the top two (viewed from rear) head bolts. Exhaust gaskets often leak. The ignition system can move out of alignment relative to the flywheel. These are some of the most common issues I see.
Use a 3/4” split steel collar and either weld a tab or drill and tap the collar for a tab that is bolted to it. Twist it and drill it to mount on one of the chain guard bolt holes. Bolt the tab to the chain guard hole, find top dead center and screw down the split collar. Just make sure your tab isn’t 1/16” material!