I was using the old style wrap around header AAP? for the 140Ls on a DZ. It has a narrow diameter pipe at the head compared to the new NMPs. I totally filled that header with carbon to the point the engine wouldn't run properly. The pipe (older hatori 120/140) was OK. I am not having the carbon buildup problem this year, but I changed a lot, so I don't know if the buildup was from one cause.

I changed the following 140DZ to 160DZ, Wildcat 30% to Coolpower Heli 30%, Old header to new NMP header, and old style hator pipe to newer less restrictive pipe. I know, probably doesn't help much since I changed so much, but something in the above mix or a combo thereof solved my carbon issue. If I had to guess, I'd say it was a combo of switching fuel and installing a less restrictive exhaust.

Cheers.