correct plug? my '78 seems to run fine with a NGK BP6HS (the '83 manual says use the BPR6HS... R = resistor)
Main jet is marked but might be worn off.. it's a #78 on the PA50II.
If this problem is cured by opening the filter box, all i can think of is insuffient air.. and that's gotta be caused by a closed choke or by some restriction between the choke and 3-holed rubber intake tube. What else /where else could restrict air that would be cured by opening the filter thing?
The otherday i thought my bike was 4-stroking .. you know that sputtering sound.. close the choke and it goes away. But then one time it didnt go away.. It was not misfiring due to a rich mix.
What it turned out to be was misfiring due to a dirty plug.