I have been having trouble with an engine I converted. It is a Poulan 25cc with XYZ electronic ignition. Most of my troubles have come from having the timing advanced too far. Sometime or another during the building process of the airplane, I ended up losing the spot where I was supposed to mount the sensor and ended up putting it way too advanced. But I digress. What I am writing about here is what happened to me yesterday when attempting to fly with this engine. Engine started easily and throttle response was good. Idle was stable but from midrange to WOT, it would tend to surge at times. Not quick surges but extended surges. I made sure it was plenty rich and proceeded to fly. On acceleration, it stalled a little but picked back up and took off. Flew a few circuits and it seemed to smooth out. Tried a few tricks and if attitude is changed abruptly like a tight left turn, the engine would sputter. Tried a loop and it died. Tried this on a couple more flights with an even richer mixture and did the same.

Let me describe the carb. It is a WT-324 Walbro. I replaced the fuel pump diaghram, the regulator needle and the regulator before mounting it. It sticks completly out of the model with the regulator forward and in the slipstream. I am guessing that the problem is with the regulator and that when something happens to change the air pressure on the regulator face like quick changes in speed or attitude where the slipstream changes, the engine starves for fuel. I have a Zenoah g20 mounted in another airplane with the carb sticking out just like this one but with no problems.

Last night, when I got the plane home, I replaced the regulator cover with a cover that has a tube soldered on in the regulator hole and ran a hose into the fuse to get the regulator out of the slip stream. I also finally put a timing wheel on it and rechecked the timing and found that I still had the timing too far advanced. It was somewhere near 40 degrees BTDC. I also moved the timing to around 28 degrees BTDC.

My question is do any of these actions sound like I am correctly diagnosing the problem or does it have another problem altogether.
And if I am diagnosing the problem, is it the timing or the regulator.


Thanks
Jim