125psi on left and about 50psi on the right. Could there be anything besides expensive failure that that's caused this? Engine won't start as a result. I bought the bike as a write-off. The bloke did have it running albeit poorly when I picked it up. My thoughts are probably a scored bore on that side. I've now paid too much (again) hahahaha. I had hoped to pinch a few parts and sell the rest. It looks like I now I have only a few dollars value in the engine, spares only, plus some plastics in good condition.
Valve clearence, (valves always open)
Head gasket(maybe change or re-torque)
Piston rings(add oil in sparkplug hole to temporary seal when doing the compression test.
Yes, pour a little oil down the sparkplug hole and cycle the engine a few times-then re-test. If compression improves its the rings, if not it is a valve problem.
People neglect the valve adjustment, but as stated when there is no clearance left the valves won't close completely. This is actually your best case scenario, as a new shim is pretty cheap fix.
Unless, you already have burnt the valves because if they dont sit contacting the metal of the head seats, they over heat. The fraction of a second they are closed they cool down transferring heat.
But that should happen only if you ride it hard for a long time.