2ltr carby problem

[Delta]

Hi all,

I need a little advice with a problem on a dellorto 40 carby - 116 2ltr.

I recently noticed a noise coming from the intake, originally I thought that it was a belt (similar squeaking sound). It turns out that the first carby was pumping massive amounts of fuel into cylinder 1. I have always struggled to tune the first carby using the mixture screws, it doesnt seem to make a difference how far I adjust the screw the eng doesnt run any better/worse.

Anywayz, I replaced the needle and seat which seems to have stopped the flooding, but while I was tuning up the carbs the eng fired back through the intake and to my surprise it actually fired underneath and behind the first carby. Gaskets look good and there isnt anything obvious.

Could it be at all possible that the carb is bleeding fuel and I have a crack in the intake somewhere or have I missed something obvious ?.

Many thanks

[Thmpar]

I would say being basicly the same as the sud down draughts that have caused me plenty of drama's, its got a blocked jet or idle circuit in the carbi itself.
Remove the mixture screw and using an air nozzle blow compressed air in the mixture screw hole, yes some fuel will blow out of carbi but this
shifts dirt etc.
a good starting point for mix screws is screw all the way then back out 1 1/2 turns.

As for back firing a flame sounds like you also have a spark problem and its trying to cross fire cylinders,have a look inside dizzy cap for cracks and or burn marks.

[Delta]

Thanks Thmpar.

We were both right . Blowing out the mixture screw holes helped, I could at least start to tune the carbs. Needle and seat + rubber intake mounts on carby 1 were gone.

Thanks again Thmpar.

[Thmpar]

no worries glad it helped to some degree the suds are bad for it as well as every other car i work on day after day.