Thanks for all the replies guys...

I appreciate it, even the ones who blame this on me.

I have checked the regulator and flushed it out and cleaned it off many times. There is nothing in it. The check valve has been cleaned and checked and is fine. This problem has existed since the very first run, It has just gotten worse. Dave at YS said it's a faulty plunger and they need to replace it... He also said it has been a problem on many newer YS .63's and they all need to have the new plunger put in, but for some reason they won't send them off seperately without fiddlin' with the engine.

The check valve theory still doesn't make any sense to me. If it can't hold pressure when the engine is off, it can't hold it when the engine is on so the pressure can't build up to begin with. Even if it turns out to be the check valve (small chance, IMO) I will feel MUCH better about running it and flying after I know the guys at YS have had a look. If it turns out to be the bad plunger in the regulator, I'll just have to come back and give all the check valve guys trouble...

Thanks again everyone. Keep it coming!