I did the test with the throttle wide open both hot and cold.
I found this table to adjust for altitude when performing compression tests:
Altitude Factor
1000 .9711
2000 .9428
3000 .9151
4000 .8881
5000 .8617
6000 .8359
7000 .8106
8000 .7860
It looks like a logarithmic curve starting at roughly 3% loss in pressure every 1000'. So at an elevation (5500'), I'd be looking at about a 15% loss.
So Ace, what would the procedure be to obtain some power but retain ease of starting? Would I pull the head and barrel, take it to a machine shop to see if it needs a rebore and then order a piston to fit that rebore? Or is that cost the same as ordering a new alloy cylinder and corresponding piston from the start?
My advice is the bore to a larger size like 535, and use a higher compression piston of high quality.
Now, it might look unseemly for me to mention our stuff here on the forum, but the fact is that we have the lightest piston made anywhere for the Bullet. This puts the least stress on the lower end of the engine. Even less than a stock piston.
Set the compression using gaskets/spacers under the barrel to something more like 110-120 psi on the cranking compression test, which would put you in the same neighborhood as a stock Bullet at sea level.
We can do the boring/honing to fit the piston correctly with a clearance which we know is correct, and we do it on custom-made torque plates which simulate the barrel being torqued on to the engine when we bore it, so that it is in the same "roundness" condition when you torque it on your engine(20 ft-lbs). Break it in right, which we can instruct you about.
The bore is always honed to fit the exact piston that you have selected, with the proper clearance. Not the other way around. You fit the bore to the piston.
Make sure that your breather is the old type which has the elbow on the left side of the crankcase, and if it has the breather on the oil tank, then now is the time to convert it to the old style. It really needs that. And make sure it has a duckbill working on the end of the breather hose.
If you want valve job work or valve guides or whatever, we can do all that, and we only do performance "Mondello" valve jobs, so it will perform better than pretty much any other valve job you are going to get. We'll make guides to fit, if you need them. Any level of performance head work above and beyond that, we can also do for you if you want.