Tuning a 450cc single cylinder engine with plenum and restrictor

[mech5496]

Disclaimer; NOT an ECU/engine guru, just aware of simple principles/concepts by experimenting in my own car.

Has your ECU the ability to control idle advance per RPM delta? If yes, try to use ignition advance to keep the idle steady.

https://www.youtube.com/watch?v=kiPow6aeb_0

BTW car looks smart.

[Owen Thomas]

Wouldn't consider myself an expert either and not familiar with that ECU, but have dealt with similar problems before.

Check for an "over run" trim that changes fuel based on TPS rate and play with it, you are probably right that there is too much fuel after the throttle snaps closed.

Also look at your ignition map and see if there are any timing walls that are keeping the revs lower (or higher) than wanted. Sometimes people put in a sort of idle pit where the spark is retarded a few degrees and a steep jump in spark advance just above that, if this area is misplaced it can cause your engine to hesitate or bog down. I'm also bringing this up because 2200 rpm idle seems a bit high so this might be something you want to look into to control that.

Good luck!