Help T5 misfiring & plug oiled

Since returning from the Isle of Man rally, my T5 classic has started to misfire badly in low revs. It fails to tick over and the plug is badly oiled. Don’t think this has anything to do with in but recently I changed the gearbox oil. The T5 has a leovinci pipe fitted, standard everything else. Can anyone advise

The oil is black on the plug.

classic symptoms of clutch side seal failure,change seal and take 4 cans guinness daily for 2 wks at regular intervals,this wont help the engine but the loose stools will be the same colour as the plug is now,try it and see [:D] [:D] [:D] [:D] [:D] [:D] [:D] ;D ;D [:)] [:drink:] [:drink:] [:drink:]

What kind of oil is on the plug? is it black?

Take out your oil filler bolt and tip the scooter over until a little of the gearbox oil pours out into a jug or something then smell it.
By the sounds of you problem you have popped the clutch side oil seal or it is on its way out at least.
If the oil smells of petrol then that is what has happened. i doubt very much if it will be anything else but email me on [email protected] and let me know.

good luck!![:smokin:]