Hitchcocks Forum

my 2000 350 bullet back fires under load the spark plug is blck with carbon tried weakining the pilot mixture but made no diffrence carb is an amal monobloc with a nondrop float fitted could it be a stuck float or could it be electical ie battery on the way out or a duff coil any ideas fellas as its getting on my wick

Have you tried dropping the needle one notch?

Are you sure it is carbon? Is it sooty black or shiny black?

the carbon is sooty blcak should have said the bike is fitted with a boyer and the battery had gone flat recently recharged but then fond a luse connections while out riding reconected them and battery shoed a charge battery is sealed for life standard size sugested by a friend could need biger battery to power the boyer indicaters etc battery is a year old

I think you may be barking up the wrong tree with the electrics. If its running rich, then as Simon says, dropping the needle valve is most likely the way to go. (BTW, to set the pilot jet/idle speed take a look at the technical notes on this site). The other possibility is that its burning oil, most likely cause piston rings or worn valve guides.
Of course, this doesn't mean that there isn't an electrical problem as well, just that it won't be the cause of the plug fouling.

will try droping the needle one notch and resetting the idle screw thanks for the tips lads il have a go on sunday as i wont have time before then as il be out on my triumph on saturday and sunday morning

ajusted idle mixture fitted iridem spark and recharged and fitted battery all seems well with billy the bullet fingers crossed thanks for the advice