How did you manage to do a compression test while one cylinder was running?!?!?!?!?!
You should take the plug out of the cylinder you testing, turn the bike off, and the gas off, screw in the compression tester, and kick it until the gauge stops going up.
Depending on your elevation check out http://www.nossmachine.com/banshee_heads.htm and the chart about half way down tells you about what compression you should be at. 155 seems low for 19cc domes, but you can check on that page and make sure. Also, do your compression check again, the right way. Usually with 19cc domes your going to be on pump gas though.