Hi,
I'm having trouble with my 1999 50CC Gilera Runner.
When cold, it's very difficult to start. Once running, it ticks over fine. When it has been running at higher revs as I'm riding, it stalls when I've come to a stop, unless I keep higher revs on it. Then when I open the throttle to pull off again, it 'bogs down' and cuts out, though it starts very easily when hot. I have to leave it for about 30 seconds untill I can rev it again without it cutting out. I've stripped the carb and given it a good clean, and that seems fine. There is an electronic choke, but I'm not sure if this is working (and I don't want to spend £50 on one 'just in case', is there an easy way to tell if the electric auto choke is working?) I've noticed that when it's being run with the throttle open on it's stand, there is a dark wet liquid coming out of the exhaust minifold. Could this indicate a problem?
So to recap my questions.
1) How can I check the electric auto choke?
2) Why could it be so difficult to start?
3) Why could it be cutting out after being revved with the throttle open?
4) Does the dark liquid around the exhaust minifold when being revved indicate anything?

All help/advice greatfully received.

Bigglesbutcha, December 2009

A up mate im not 100% but this could have sompthing to do with your piston rings as the hotter the barrel gets the bigger it get so therefore it may need a new set of piston rings

arron jones, July 2010

spark plug might be gone did you put anti freeze into the bike

mark, January 2010

yes a lean mixture means too much air and not enough petrol in the fuel/air mixture that the carb makes.the reason the brakes seize is the corrosion builds up behind the dust and piston seals in the brake calipers you need to pump both pistons out and take the seals out clean both the grooves that they sit in out with a bit of bent wire or small screwdriver and then clean the seals and pistons grease the seals and put them back in make sure you have the bleed nipple undone when you put it back in or you will be trying to compress air and it wont go in.

adam bike doctor, December 2009

Thanks for the advice so far. It failed its MOT yesterday on binding front pads, so I need to sort that out before I can work on the engine again. If I could just clarify a couple of things. When you say a 'lean' mixture, do you mean to little air, or too little fuel? The oild pump isn't one thing I'd thought of. I've never even looked at that before, but I'm sure I'll have a look for it and let you know how it's going. I've only had the bike for a week, so not sure what mods the previous owner made. I'm starting to get suspicipous that he's messed with the carb, and possibly changed the main jet.

Bigglebutcha, December 2009

the symtoms point towards a lean mixture so i would suggest checking the air filter pipe work for leaks or splits and maybe the vaccum tap.have you checked the main jet/idle jet and choke jet its common for a choke jet to be blocked on these gilera and piaggio scooters also they get lost easliy if not noticed when blowing the float bowl with a hight pressure air jet i have lost loads of them :)The black liquid you can see at the exhaust joint is burnt oil/petrol mix its normal but excessive amounts are due to either bad running as rthe motor doesnt get hot enough to burn it or slow riding habits also a over tightened oil pump cable can cause it and this will also cause a weak mixture so check the oil pump is operating ok throught the black inspection hole in the transmission cover make sure the outer cable is correctly seated in the cable adjuster there too.let me know the outcome.

adam bike doctor, December 2009