Yamaha F50 missfire :(
I have a 1996 F50 with a persistent misfire. I originally took it to a Yamaha dealer who diagnosed a faulty carb on cylinder 4, from there it has cleared a high rpm issue but has a bad misfire upto 2400rpm, to the point that from initial start up drops onto 3 cylinders and only recovers to 4 after a high rpm run, from there on it pops and bangs at any rpm below the 2400 mark. So far, compression has been checked and is normal across the 4 cylinders, carbs have been stripped numerous times, cleaned (both with carb cleaner and ultrasonic bath and re-balanced. Plugs replaced, coils swapped out.
The fault seems to lie with Cylinder 4 which when the misfire occurs the HT lead can be removed with no obvious change of engine note, against the other 3 which are definitely firing.
Any assistance greatly received.......