I was going to say it could be the spark plug. I was married to a drag car racer for eight years, so I spent a lot of time around cars haha!! Well, I hope you have managed to solve the problem for good. Nothing is more frustrating than having a vehicle that is giving you problems.

I actually had an unfortunate experience myself recently with a welsh plug on my car. Something I have never experienced before. The car is old, so the welsh plug had rusted and it fell out while I was on the road. It was the weirdest noise (and smell actually) and my car temperature suddenly went straight into the red.

I was petrified that it was going to blow my gasket, but clearly someone was watching over me because at that moment I just happened to be at a traffic light which was directly opposite a petrol station, so I drove straight over and thankfully did not cause any further damage.

It was NOT a fun experience... but was just glad that it did not turn out to be something more expensive to repair.

I hope you manage to get your bike all sorted!