ran when parked

[PGlaves]

If it has the stock Bing Slide carbs, I'm assuming you had them set at WOT before doing the compression test?

That will get it close. Taking them loose at the head works even better.

[edzr60]

On a couple of old Triumphs (one mine, others friends'), releasing the tickler just a moment after gas flowed out seemed to be right... Considering the state of "technology" of their carbs and ignitions, it was important to not flood it or sprain your ankle.

Might the low compression be because the valves were set with the crank mark at TDC for the "wrong" cylinder... twice...?

I remember my old Triumph. Everywhere I went my hands smelled like gas. I've had 7 airheads in the last 40 years so I'm aware of the danger of setting the wrong side. In fact, one side was set incorrectly on this bike by the PO. I vaguely remember a service manual out there that did not inform the reader to rotate the motor to set the other side.

[MANICMECHANIC]

Depending on how the bike was put away, it's possible that you may have stuck rings causing the low compression. Noting that this is a boxer engine with horizontal cylinders, it is still possible to squirt some oil through the spark plug holes, spin the engine a couple times, then check if the compression values change. Or if you feel really comfortable, put the bike on its side to add the oil. Might be worth a shot. Then if the compression does improve, maybe the bike will start and the rings will free up after the engine gets some heat in it. My experience has shown that engines with compression less than 100psig are very hard to start, so check everything else first before trying this method. It will get smoky if it starts.