Speed kit manifold fasteners/right hand carb.

[CAB]

Hello
I have a pair of speed kit inlet manifolds that I intend to eventually fit to my 650 CSR even though I know it will be more hassle than it is worth....

Anyway I have a copy of the parts list required for the conversion and it lists 4 x 018873 allen screws. Presumably these are to attach the carbs to the manifolds? Can anyone confirm that this is correct and also what size and thread should be used. I'm assuming that there must be a reason to use screws instead of studs. The only thing that I can think of is that there is not enough clearnace to get the carbs on over the studs.

The right hand carb is listed as a 389/49 and from memory this is the same as the original single carb. I have been told that the right hand carb should be of the 'chopped' float chamber type. Which is correct?

Thanks

CAB

[Don Madden]

The 1962 spares list supplement shows adding the 398/74, not 398/49, monoblock for the R/H side & it is a chopped float type. It is 1-1/8in, same as the L/H side. Can't answer about the screw fixings but choose allen head screws that protrude beyond the manifolds the same depth as the studs for the single carb do. Cheers, Don.

[petert120r]

The allen screws are 1 inch 5/16" BSF (22tpi). You will also need a banjo to take the fuel from the base of the L/H carb to the R/H chopped one; it's also a good idea to fit a float chamber extension to the L/H carb as it has to feed the other one as well.Edited by - petert120r on 06 Jan 2011 09:58:21 AM

[CAB]

Thanks gents.

I have just looked at the Amal site and it lists a 389/73 and a 389/74 for the speed kit. Hopefully the 389/73 is the same as the original 389/49 (with different settings) and all I need is the chopped 389/74.

Good idea about the float extension. There is an old pair of Norton 376 Monobloc 650 SS carbs at my dad's, I think these have the extended jet holders and banjos to connect the carbs together.

CAB

[petert120r]

The manual gives the following settings for twin carb set-up
Pilot jet 25
Main jet 280
Slide no 3
needle 4th notch from top

[rayswadling]

As an aside, I managed to obtain one of the twin-carb manifolds a while ago.

Currently, I have an engineer friend making a new pair using the one I have as a pattern. There will be some "fitting" to do from the basic shape but how much I don't know yet.

Haven't seen the finished article yet and no idea when he will complete them as he is doing it as a favour.
Not sure how successful it will be, and they won't look original but they are being done on automated machines so they will have the pattern stored should anyone be interested.
I'll post photos once I have them.

[bailequaile]

Hello there,

I recently fitted the twin carb’s to my Model 31 and have found the process to be pretty painless. Once they are tuned in they run like a charm. Even if they don’t they sure do look pretty?
Initially I tried using shortened studs to hold on the manifolds but with that method there is no way of removing the manifold and carb as one unit. As you guessed there is no room to slide them off with the oil tank and tool box installed.
I eventually shortened some spare rocker cover screws that had the same thread.

The carbs and manifolds I bought were from a factory fitted bike so if you need any information about settings etc ask away and I will run out and have a look.

Good luck

Adam

[bailequaile]

Oh I think I misread your post.
I was thinking about attaching the manifolds to the heads.

As for attahcing carb to manifold - My manifolds have four short studs that the carbs slide over. They are short enough to allow removal of the carbs withiout having to take off the manifolds as well.....just! It's a tight squeeze in there.
I can post a photo if you want.

[CAB]

Hello

Thanks, photos of the installation would be very useful. Did you have to make up your cables?

Regards

CAB