got a yb100 that when it is in fourth gear seems to miss a beat like the clutch is slipping but clutch has been apart and is ok.new plug points and plug cap even adjusted points with dial gauge on just before tdc.check all wiring incase it was shorting out all ok.it is just a split second miss.you ride in third gear to as fast as it can go and all is fine.anybdy any more ideas or am i going to strip engine to see if fourth gear has tooth missing???

Moved to the correct section.

ah ok sorry where am i now haha

In the workshop, not the section for help with the forum usage.

Is it only 4th?

Have you checked the carb for crud that may be floating about and blocking a jet?