LCGB Forums

Got a Scootopia 22mm carb on my series 3 and if I don’t switch the fuel off after a run there is a leak underneath it on the floor…what is causing this? The carb is about 18 months old but only done maybe 200 miles

Possibly the float catching on the inside of the float bowl stopping it properly floating on the fuel. When this happens, the float needle won’t seal.

Take the float bowl off and look for witness marks on the float or for any reason why it would not seal the float needle when the bowl is full of petrol.

Also, float needles can just wear out and need replacing. This won’t be the issue with yours, well it shouldn’t be. You can test it by leaving the float bowl off, support the float at its uppermost point with your right hand and switch the petrol on. Petrol should not come out until the float drops, if you move your finger.

Glad to see you sorted this

If it is an old carb that has just let the petrol evaporate, Sticky’s book has a good tip which I have only just read. The brass housing for the float needle needs polishing as it gets encrusted with muck making the needle stick. Do this with an ear bud dipped in chrome polish and attach that to the end of drill. I have done one this week.

It won’t necessarily resolve all issues as, if there is muck in that housing, it stands to reason that there may well be encrusted muck in the internal passages. They may, if you’re lucky, be cleared with ultrasonic cleaning.