Compression is engine moving with motor/kick/push.
Leak down is the cylinder is going to open either valve you find TDC. Why? Upon air going in it depends how far you threw the crank or stopped before TDC even though it looks like it.
So the deal is, go past the stationary case half so the piston moves on the power stroke. Why? Now you want the bike in 1st and a long screwdriver thru the mag spoke and the swing arm. Why? This forward move has your mag webbing settled so when the air comes in, piston goes down, crank to trans to chain to wheel is locked this way, and no way the crank opens the exhaust valve. Connect the air so the load is soft at the rim, no valve opens, you are good to read the leak.
How do I find #1 TDC? I blow into the plug hole and if it stops and fills your cheeks, you found #1 compression. Sequence goes 1-2-4-3 when you turn the crank that 180 after the other.
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