Carb Parts Mixed Up

Oh, I’ve really done it this time.

Per our manual “Do not interchange vacuum chamber covers, springs pistons and jet needles between carburetors.” and “#1 and #3 carburetors use thinner jet needles and shorter springs than the #2 and #4 carburetors.”

Wish I had read that sooner.

Well, I know the shorter springs go on the rear, that’s an easy one.

The vacuum piston/diaphragms all look the same to me, but the ones in the rear were torn, so that’s an easy one to identify from the pale grey Hondabond patch job.

The problem(s)?

The jet needles look identical, and all 4 have the same letters “HB” stamped on them. How can I tell which are thinner, and thus belong in the rear? They all measure 2.49mm at the base, and the tip is hopelessly impossible to get a consistent measurement location on.

Vacuum chamber covers are also all identical looking, and are going to be sent off to be chromed. How do I begin to identify which set is for the rear?

Any help is appreciated/mockery is deserved.

Thanks guys!

Sorry, the jet needles read “1HB” or “IHB” on them. Or maybe that B is an 8. But they definitely ALL have the same thing stamped on them.

hi, ive just cleaned and replaced my carbs back on the bike, looking at an old set of fe carbs which ive been robbing a few bits off its. 150 main jet and long springs on the front carbs and 145main jet and short springs on the rear, i cant see any difference with the needles but ive allways thought they had a slightly different taper on them, there is some wrighting on the top of the needle which i cant read, my eye sight isnt what it used to be,

as for why the difference in front and rear, overheating is a issue with these bikes especially when stood or in trafic, think honda was frightened that the rear cylinders would be especially efected by lack of air cooling, plus maybe better carburation with the shorter rear exhaust pipes…

anyway got to dash, got to put fairing on bike and tidy garage,

The vacuum chamber covers are all the same as far as I can tell, same as the needles even though they do go on about that in the book.??
Something I’ve wondered about as well, the originals all stamped the same as you say but I could never see any difference.
When you look at the parts list they have four needles required under one part number and four covers under one part number, suggesting they are all the same.
all a bit strange really!

When I did mine up I had four new needles all the same supplied in the OHaul kit.

Probably the reason not to mix up the pistons is wear patterns matched to each carby but shouldn’t be a problem really.