ORIGINAL: mc1982
when i turn the engine on and start advancing slowly at around 1/4 thorttle when its near 4000rmp it works roughly then can suddenly cut out. I've notice if i advance it faster towards full throttle and leave it there for a bit then idle and go back up slowly the problem is gone. This happens now every time i turn on the engine.
Sounds to me like the regulator is set a little too rich. The "rough" running is indicative of flooding. Usually a rich engine will just cut out after a few seconds, because the glow plug is drowning in fuel, becomes too cool to fire the fuel charge, and the motor just quits. On the other hand, a lean engine will usually speed up for just a second or two just before it quits.
The reason the problem seems to disappear after you run the engine up for a bit may be because the engine temperature is coming up, which will make it run a bit better in a rich condition. Once you get it hot, especially the head, it can tolerate the rich condition a little better than it can cold.
Try turning the regulator screw in (clockwise) about 1/8th turn and run it again. Readjust the high speed needle valve after you do, by running the engine WO, adjust for maximum RPMs, then richen it by turning the high speed needle back out (counter-clockwise) three or four turns, or until you hear just a slight drop in RPMs. If that helps, but doesn't completely correct it, do it again.
David