Anyone know why this would build up so much carbon after about 3hrs after rebuild ?

 

Probably too much oil in fuel/oil mixture, or rich air/fuel mixture in carb. The big question is why you needed to take the cylinder off 3hrs after rebuilding the engine.

 

Good question... noticed the head nuts had come loose so wanted to check head gasket was ok. Also noticed that the replacement head bolts were about 10mm shorter than the originals which could be why they came loose. New ones ordered. Will try adjusting the circlips on the needle. Cheers

 

Please install Suzuki studs. As you see, the cheapo studs stretch.

 

I've ordered genuine ones. Hopefully back together tonight