Some confusion here, you say it idles at normal speed but turning the L screw in or out has no affect on idle speed? Does it accelerate normally to high speed and runs at high speed but you think it is running too rich and that's why you are trying to lean it out with the H screw? Also, an engine with a true compression reading of 50 psi should not start, are you using a gauge that is meant for small engines with the valve at the engine end of the gauge extension? Can you be more specific about "runs terrible"?
Some confusion here, you say it idles at normal speed but turning the L screw in or out has no affect on idle speed?
you turn the L screw a lot and even then you hardly notice an increase/decrease in rpm or a misfire. same with the H screw.
Does it accelerate normally to high speed and runs at high speed
Yes but not cleanly, little boggy and high speed is not crisp, and it's -20c outside. I didn't put a tach on it, it may not be reaching spec rpm but it does rev up.
but you think it is running too rich and that's why you are trying to lean it out with the H screw?
Yes, you can't get to that lean spot where it cleans up.
Also, an engine with a true compression reading of 50 psi should not start, are you using a gauge that is meant for small engines with the valve at the engine end of the gauge extension?
Believe me it ran, I have a video of it running and the compression test, for the dealer. I thought it was the gauge too but I stuck it on my older BG55 and got 137 psi.
Can you be more specific about "runs terrible"?
Rich, poor throttle response, sounds like it always is four stroking. And often it instantly dies when you let off from wot.