I recently put the 60cc cast iron kit from treatland, as well as the MLM sidebleed pipe on my FA50, and upjetted my stock carb to 82.5. Everything else is stock and I’m still running the oil pump as general consensus seems to be that they are reliable.
I had it going 32 for a while with no problems but the other day, while going at full throttle for long stretches, I’d lose power and slow to about 22-25 mph... it felt the about the same as if my gas tank was running low. Slowing down for a bit would let me climb back up to 32 again so I kept riding and after it happened a few times, the engine went SKERRR (like high pitched nails on chalkboard noise) and shut down... it kicked up after a few minutes and I brought it home slowly, and there was a slight metal on metal noise coming from the engine every so often.
It’s been able to get to 32 still, and my dad suggested maybe I was running lean and getting the engine too hot so I upjetted to 87.5 main jet, and put the needle clip at the richest setting but it will still will slow down after long stretches at full throttle. Maybe worth noting is that these changes to the carburetor had very little effect on performance, ie top speed is still 32 and it takes about as long to get there.
I’m gonna take the engine apart on Monday when my new gaskets come but has anyone had this happen before and what did you do? I couldn’t find my setup in the tuning spreadsheets on the wiki so any input from someone who has done this is appreciated... (edited)