ORIGINAL: NJRCFLYER2
Steve:
There's something else going on with Matt's 33GT. We even went to a different brand CDI unit it on the assumption that the stock CDI had some sort of minimum RPM code built into it. It really just acts like a fuel draw problem, my theory being that those 4reeds need more negative pressure than a typical 2 reed setup, possibly because their individual surface areas are relatively small, though their combined surface area is probably larger than a comparable sized engine's 2 reed system. Matt's engine behaved well for the first 3 or 4 flights, then became a problem. We looked at various possibilities, leaks, warped reed block and the like, and it really didn't solve anything. It will be interesting to see what comes back from the repair.
Interesting that it was fine for the first few runs. If it were the neg pressure thing I would think it would have gotten better. I doubt the reeds would have any break it but if they did, they would only get more flexible and as the ring seats the neg pressure would increase and make the reeds come off the reed cage even better. It would also make them seal better too. Difficult to diagnose an engine with a different brand ignition. It's hard to know if the advance curves are compatible and weather to set up the sensor at TDC or 28 degrees advanced as was the case when I set up a DA 50 with an RCEXL.