Thanks in advance for your help! Bikes running pretty well overall, had it out for a 30-mile ride this morning. Sunny day in Cleveland! Bike seems to be running a bit hot (to my knowledge) head temp gauge attached on top of spark plug is reading between 365-400 at WOT on flat ground. I've got the Airsal high performance 50cc kit, 15:15 SHA with derestricted intake manifold and a 70 jet. No other engine work. Stock exhaust. Running about 32mph flat out. There seems to be a bit of "four-stroking" (again, to my ears) at top speed. I'm wondering at this point if the exhaust is the limiting factor in the system, but I'm not sure. You might have a better idea than I. I have a recording of the engine sound at top speed attached.