Scooterotica

alright lads, i have an issue i cant seem to solve so was wondering if anyone else has had this problem and solved it, i have an RB20 with 30mm dellorto flatside and franspeed pipe, back end of last week it i noticed the bike revving a bit high at idle, revs wont drop off as normal, ive checked everything i can think of, checked the rubber for any splits, re-greased the cable incase it was sticking, stripped carb down but nothing has helped, turn choke on slightly and the revs will drop off so could it possibly be an air/fuel mixture issue? was also thinking a worn throttle slide? the tickover screw is inaffective, wind it in and out and it makes no difference, im running out of ideas here, anyone got any suggestions?
thanks in advance, John.

air leak...

+1

Could be head or base gasket leak, manifold, carb rubber etc, you need to go through it all and make sure.

+1 magneto oil seal.... also

Pressure test first......be a shame to strip the engine and replace the "suspect" seal and find it was the other seal.....

thanks lads, appreciate your input, i was thinking today about the head and base gaskets, although the carb rubber looks intact i am going to change that anyway as this one has been on for about 8 months and for the sake of £15 its worth eliminating, will order some new head/base gaskets as well as a new exhaust outlet gasket at the same time, fingers crossed that solves it before i have to start stripping the engine down!

Look at the thread on here for the low cost pressure test..... better to be sure if you have a leak or not....

I had same problem early this year after checking & changing various items it turned out to be mag inner oil seal

it was the exhaust gasket and also found 2 splits in my expansion pipe, one near the outlet just below the spring loops and one a bit further down, fitted a new gasket and used an exhaust bandage to seal the splits and now ticking over fine, got someone to weld the exhaust for me this week

Result....