CARBURETTOR JET ASSEMBLY QUESTION

I am dismantling my SU carbys (HS4). I have unscrewed the jet assembly from the float chamber but it won't separate. How do I take it away from the float chamber (I'm guessing it's just gunked-up)?
Thanks

Roger just wait till one of the experts chimes in - it's not gunked. There's some sort of flair fitting where it sits in the bottom of the float - that much I know but as to the actuality I can't advise you because I got my carbs done by an old-time carby guy.

Once the bottom fitting is removed from the float bowl it should pull out.
Dont stress the flex line too much. You may want to remove the bolt holding the float bowl to carb body to have a little more wiggle room.
RS

Roger,

Don't forget to remove the small self-tapping screw that holds the choke linkage to the plastic shoulder of the jet. Otherwise, once you loosen the small (7/16 IIRC...) fitting at the bottom of the float bowl, the line should pull out. Note that there is a small o-ring that seals the plastic tube into the bottom of the float bowl. Over time this o-ring can get petrified (not sure what it's scared of... :D), so you might have to pull it a bit. And if you're into the job this far, you're probably going to replace the jet anyway, which would be a good idea. Suggest you use genuine SU jets and not the lesser-quality Royze jets, and do note that the jets are "handed" and marked with colored bands to designate which goes forward and which goes on the carb to the rear...

Dick

Edit: The guys already posted good answers above, but I'll leave mine here for what it is worth. Sorry, I'm a slow typist.:)

There is a small rubber o-ring at the very end of the flex tube. It is backed up by a thin washer and the brass fitting that you have already loosened.

The brass fitting, when fully screwed home, pushes on the washer which then pushes on the o-ring and that O-ring is forced into a beveled orifice that is part of the bottom of the chamber itself. As it is pushed, the o-ring flares and distorts making a good fluid seal.

Over time the o-ring hardens and begins to solidly grip the end of the plastic flex line and that is what you are experiencing.

Go ahead and tug the flex line out. The o-ring may or may not come with it, but if it doesn't, use a sharp pick to dig the remains out of the hole.

Replacement is easy.

Pull the metal coil shield back from the end of the plastic tube and push the end of the tub along with the o-ring and washer up into the opening until it bottoms out. Hand screw the nut into the opening until you feel resistance. This will hold the o-ring et al in place. Insert the metal jet up into its holder making sure that the flex tube does not get kinked or twisted. Go back to the float chamber and fitting, and again skinning back the coil, continue to screw the nut in while exerting a little pressure on the plastic tube in order to make sure that it maintains a good seat at the other end. Finally use a 7/16" or close wrench to snug up the nut. Tighten it well but don't bust a gut doing it, otherwise you will screw up the rubber and the seal will be broken.

BTW: Make sure that you are using the correct jet assembly. There are differences between the one that goes on the front carb and the one that fits the rear carburetor.

Jack

Twiggy,

Guess my post shows that I'm a fast typist but slow thinker... :D

Your response is much more detailed and helpful... (tu)

Dick

Don't forget to install the small flat washer on the fitting side of the gland/"O" ring if you don't the fitting will destroy the gland.

don't overlook the possibility that the previous owner put some glue in there to help seal a leak.

Thanks to everyone. My confidence level has just risen tenfold. I was about to just screw it back and not bother.

Jack, you're giving away all of the secret tricks of the trade. Someone will be sent to deal with you. Expect him shortly. RAY

If you are talking about the fuel tube going into the float lid, they get stuck over time, give a good yank, you'll be replacing that anyway, also pay close attention to the rubber gland, they often stick and remain with the float bowl if you don't catch this and the old gland stays in place you will definately have a leak when you get done, use a pick to pluck the old gland out, it's kinda like forgetting the old rubber o ring on oil filter and it staying in palce when you instasll the new oil filter. Hope this helps

You may need to look hard to find a new gland by itself (what Jack called an O-ring) as they usually only come with a new jet assembly. Being in the UK though you might be able to get one (instead of a bag of them) from Burlen. I'd suggest getting several, along with washers, and keep them as spares because this is a recurrent issue.

Or, look at you needle with a strong magnifier...if you see lots of scratches on it, you may be in the market for a new jet (and needle) anyway as wear on these things makes it really hard to properly tune the car.

Joe Curto dells new glands and the brass washers separately, I keep extras in stock for my rebuilds and for the race car.

There's a a guy in our car club with a Bugeye with a 1275 and twin HS2s, he had been living with dribbling float bowls for years, and one night I heard him complain about, I ask him if he was using the proper part, he told me he was using o rings he ehad sources locally, I told to call Joe Curto and get the right viton rubber glands and brass washer and he would cure the problem, he did, and it never leaked again. That guy now think I some sort of hero for helping him cure this issue, but it was so simple, just use the proper parts,. Joe can put them in regualr envolope and mail them to you, it always a good idea to have extra needle and seat valves as well.

Thanks Hap, I'll bear that in mind. I daren't order some yet as I got wrapped over the knuckles tonight for spending yet more money on 'that bloody car' :) (I ordered 2 x servis kits from UK). Once the dust dies down I'll follow your suggestion.

Roger I assume you bought the small service kit - I bought the one with the new butterfly spindles which as I understand it you have to 'ream to fit'. After I got it I decided it was too hard for me so I got them professionally built (as I mentioned)only to be told that they usually fit an oversize on rebuild - I assume their parts come from SUMidel rather than Burlen ( but I got mine from MGOC) - just something to bear in mind once the dust settles.