Stutter when ignition is switched off

Hi all!
I have a 1.1 formal e, on a whole the engine is great has a few things that need sorting like it has to heat up when it's cold before it drives nice but after a 5 min idle drives like an absolute dream. However yesterday when I switched the ignition off it started stuttering, it's not every time but enough to play on my mind. The carb is a aftermarket and im sure its a dellorto set up, I currently looking for a carb rebuild kit for the original (if anyone knows were to get one help me out) but I just want to get it sorted or know if it will harm it? Cheers

Jordan

So, it's trying to carry on running after the ignition's off?

That's a timing issue. (Too advanced IIRC)

Yeah I thought it would be something along them lines, it was just bizarre how it suddenly happened, il have a play tomorrow! Thank you!