Twin Carb Manifold problem.

[LJ.]

Can anyone with twin carbs advise how they got over the problem with fitting the manifold to cylinderhead and carbs to the manifold? There appears to be a protruding part from the manifold on both sides of Manifold and does not fit into the mating part. How did other owners get over this? Grind off the protruding part? (which I dont really want to do) make up a quarter inch gasket? or enlarge the hole for it to fit in? any other ideas please?

You can see exactly what I mean in the picture where red arrowed...

[RichardL]

LJ,

I'm wondering if the protrusions are part of the casting. They look like they could be made from steel tube. Is is possible they were used in the sand-casting process to provide smooth-finished bores and, then, meant to be removed? Maybe if this were the case, they would fit inside the bores and carbs anyway. Well, you can see I really don't know.

Richard L.

[jfligg]

Hi LJ
  Here is what I did.  I used a couple of heat suppressing gasket that I use on my A10s.  I am just waiting for spring to hook up fuel lines and road testing.  http://i30.photobucket.com/albums/c341/jfligg/BSA/097.jpg

[Brian]

Unfortunately fella's you all have the incorrect carby's. The correct carby's have a recess in them to let the tube go into them, the same as the cyl head. I dont have a carby body at the moment to photograph. The inside dia of the carby should be the same as the inner dia of the tube, 7/8". You could probably machine the carby body if you have a lathe or get someone to do it for you or remove the piece of protuding tube so the carby comes up flush to the manifold.

[olev]

Brian's right .. again.
cheers

[LJ.]

Thanks Guys! Brian your indeed correct after a look around on the net... Thanks Olev for showing your pic which clearly shows what Brian says. Right! well although wrong I think i'll stick with the 276 types with 15/16th bores for now, I cant see any harm in using them. Bet Jeff is gonna be watching closely! 

There is still the problem with the manifold fitting up against the head... As you can see in the photo my ports are not recessed to take that sticking out bit on the manifold. I see Jeff had no problem as the manifold fits close to head. How come?  ???

So far this project costing a bit but not too badly...  £35 quid for the carb from an autojumble which seems in good nick. A big bag of parts ordered today from Hitchcock's Motorcycles Ltd and consists of Main Jets (140) Needle Jets (107) Taper needles, throttle slides (4 cutaway) etc etc. £119.12

But the main thing is that its fun! 

[Brian]

Its been a few months since I put my carby's on and I've drowned a few more brain cells since then so I went and had a look at the spare heads I have and the head isnt recessed. I couldnt remember if they were or not. It must be only the carby side that has the spiggots. The steel tubes inside the alloy manifold come out, I made new ones for mine, so you should be able to heat the manifold and drift the tubes through until they are flush on the head side and then grind off the protuding piece on the carby side so your carby's will fit. Good luck.

[trevinoz]

Have a look at this head. You can clearly see the machined recesses for the spigots.
I ground the ports of another head to take the manifold as it was a very good one with no broken fins but have since found this one.
  Trev.

Brian, it's that Cooper's that is the problem. I stick with Dr. Toohey!

[Brian]

Maybe I'm not going mad after all. I was sure that my head had recesses for the manifold spiggots but when I looked at the spare heads they didnt so I thought my memory was going. The Star Twin must have a different head which means my spare heads are off single carb models.

Now that I know for sure that the Coopers isnt doing me any harm I can drink a lot more !!!!!!!! I was worried for a while there......