low comps on right cyl

[TassieGS]

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.

[Armandorf]

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.

[chris900f]

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. 

[Armandorf]

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.