I have a Minarelli V1 engine kitted with a 75cc Polini Kit with a 16.16 SHA carb currently jetted at 70. A couple days after kitting the bike, the engine started simply dying at low RPMs. Sometimes the bike will idle as long as I have the idle screw all the way in. But as soon as I brake the chain, the engine will die. At first I thought it was the clutch catching, but when I took the clutch apart everything looked normal.
I have changed the transmission oil to 30 weight non-detergent oil. I'm not sure what was in it before. After kitting my bike and the first time it shut off on me, when I went to check the transmission oil, it spurted out of the case, which means an excessive amount of pressure was built up around the clutch and transmission. The cause of this was due to the fill bolt not being stock and didn't have a hole to allow pressure to escape. I have since fixed that.