Back fire through carb

Right. The vacuum barbs are on the manifolds not the carbs. T.

QUOTE="Torchard, post: 745264, member: 37169"]
I’ve not had much luck confirming their year as I can’t find photos that look exactly like mine e.g. showing the vacuum ports. But I think they’re 78-79 era. However, in support of what you’re saying: they do have the slide as per above and I think the needle didn’t match the 78-79 spec. I think it was from the earlier model. They were jetted to 78-79 spec.
[/QUOTE]
 
Well, it's pretty easy to tell the difference between a '78-'79 carb set and the earlier ones simply by looking at the intake bell where the air filter mounts. '77 and earlier carbs had external float bowl vents, a nipple sticking out of the side of the carb body. In '78, that external nipple was eliminated and the vent was moved inside, around the lip of the intake bell (two large holes @ 3 and 9 o'clock) .....

LabeledCarbMouthsSmall.jpg


Even if you have the later '78-'79 carbs, if they're fitted with an earlier slide and needle, you should probably base your jetting on that.
 
Thanks. Yup. Older set. Guess I better dial back the jetting. It came with increased jets - equivalent to stock 78-79. I’ve since gone up further to 35 pilots and 140 mains. Ran ok except some issues at high speed. T.

Well, it's pretty easy to tell the difference between a '78-'79 carb set and the earlier ones simply by looking at the intake bell where the air filter mounts. '77 and earlier carbs had external float bowl vents, a nipple sticking out of the side of the carb body. In '78, that external nipple was eliminated and the vent was moved inside, around the lip of the intake bell (two large holes @ 3 and 9 o'clock) .....

View attachment 215680

Even if you have the later '78-'79 carbs, if they're fitted with an earlier slide and needle, you should probably base your jetting on that.
 
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