Misfire on Griff 500 with light throttle and sub 1500 RPM

[sjpgodfrey]

Hi, I have a bad misfire when at very low RPM (sub 1500) and on a very light throttle.

It goes as revs rise and more throttle is applied.

I have seen one end of the vacuum advance pipe is split so will replace it. Could this be the ultimate source of the mis- fire?

Simon

[Belle427]

Unlikely but the hoses are always worth checking as they perish with age, the fuel pressure regulator is another worth looking at.
99% of the time its down to ignition components, the extenders being the favourite if it still has them, they can be removed for test purposes if the leads reach the plugs.