Low compression on commando 273 with 13000 miles??

Was the engine warm when you did the test? Also, did you hold the throttle wide open? Did you crank it enough to build pressure (at least three to four revs)?

I'm no expert, but I think your next step is to squirt some oil into the spark plug hole and see if the compression increases. If it goes up it indicates rings.

You could also perform a leak down test to see if the valves are leaking, but if it were valves (or head gasket) I would not expect the compression to be down evenly in all cylinders. Maybe do a leak down on 2 and 7? On mine I was able to hook my compression tester fitting to a compressed air source and then listen/feel for air escaping from the exhaust pipe (exhaust valve), carb (intake valve) or oil filler cap (rings). You should get some leakage past the rings, so you have to decide if it's excessive.

Do you have an oil pressure gauge, or just a light? It might be worth getting an oil pressure gauge hooked up to confirm you've got good oil pressure.