Modern Vespa

Hi ppl. My scoot has developed an ignition running problem. Trouble starting, changed plug twice, it will start with some persistance and will not tick over. it will accelerate but loose revs and it back fires and stops. Plug is dry black sooty when i check it, i have purchased 2 new plugs and still the same with each one. fuel seems to be getting there as i can smell it if twist accelerator grip when trying to start. Have no warning lights or anything to sugest there is a problem. Anyone had same issue who can shed a light on this please. cheers

weak battery,

Yup.

New battery fitted, someone suggested a sensor on fuel. Anyone had this go with same problems

Does it sound a bit 'rough' when trying to start? If so, a failing sprag clutch is a likely culprit. This is the 'freewheel' clutch between starter and engine. Eventually they disintegrate enough that the engine will seem seized. Replacement is a bit of a chore.

It all started when I was riding back in rain, thought water had got somewhere it shouldn't. Left it to try under cover for 2 weeks, it try to start but just turns over when I try to put small revs it then starts but if loose revs it dies and backfires. If when it goes I hold revs open a bit it will run but feels sluggish. Again after getting engine warm I loose revs it will die backfiring. I gave it full service changing belt, put mallossi variator on, with the new clutch spring, everything and still does same

check your spark plug and probably replace , also look at the spark plug cap really closely , might be cracked thus causing arcing and not getting enough juice to the spark plug.

Used 2 new plugs didn't make difference.