this is driving me nuts. my beater 185s drips oil out tje pipe, runs great, smokes like a freight train, but runs great! now my other 185s checked valve adjustment, checked timing, new plug, rebuilt carb, new filter in the stock air box idles good, but has a flat spot right off idle, full throttle it runs okay, has a occasional pop out tje exhaust. I tried the oil burner carb, same thing.
the weird runner has stock cdi, new spring in the pulse generator, stock coil.
Old smoky has a 13 dollar china harness with cdi, coil plug wire. I haven't swapped the harness yet (don't want to cut the factory harness) but could it be the stock 40 year old ignition parts? jim