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Manx 350 Carburettor - discuss!

Submitted by william_monteith on Fri, 14/07/2023
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So, here is my tale of woe. 1947 350 40M engine. As fitted to my 1947 40 Manx.

Restoration is going well. However I have now found a major issue with the carb fitted to the bike. I am aware that what is fitted was not original. It is a 10TT 36R. On stripping to refurbish I found that the main carburettor body, where the knurled ring screws onto the body to hold the carburettor top is completely U/S. There are bits missing from the thread and the knurled ring has had a slot cut into it and was gripping the thread by dint of a type of Jubilee Clip around the periphery to hold the ring on to the body. In short, the main body is scrap.

I can find plenty of 10TT's on the web but it seems the issue is the bore size. Most of the ones out there are  1 5/32" bore as fitted to the 500's etc. I cannot find an 1 3/32" bore anywhere. I will be scouring the autojumbles until I can find one.

However, Bacon lists the correct carb as an 1 3/32" RN carb. But I have been warned off of going down this route, even if I could get one! Likewise a GP. But a web search for an 1 3/32" one of either of those has thrown up nothing.

A very knowledgeable Norton Dealer that I know has said that a concentric would be better than the RN or the GP! I don't particularly want to go down this route. Even though my bike is a bit of a "Bitsa" I would like to get it close to correct.

So, the question is, what are the alternatives whilst I try and track down the correct carb? Or, ideally, does anyone actually have a spare carb or surplus body that I could purchase?

Over to you.

Thanks in advance for your sage words of wisdom.

Bill

 

Submitted by mikael_ridderstad on Fri, 14/07/2023

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My -59 40M came with a 35mm GP with same thread damage. Originally it had a slightly smaller one. He who raced it in the sixties recommended the slot and jubilee solution. Unable to find a same size GP, I ended up fitting a Gardner 35mm. Don't look right but with help from other racers got it running well. It seems that the Manx gradually got larger and larger carburettors. So I think that your bike could run well with a 1 5/32 TT. A 40M is lacking power at low revs anyway.

Float chambers. The matchbox I got from Burlen didn't give enough at long straights. Fitted a Gardner one, no more problem. But hopefully you have a decent more originally looking one.

Submitted by robert_tuck on Fri, 14/07/2023

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The Dellorto SSi  is pretty much a copy of the TT ,but they can be a bit pricey and spares a bit scarce. If you want to be really different I have a brand new Bowden 29  !  , The Works tried them out in practice one  year but chickened out when they realised  they would be in trouble with Amal if they won !.

Submitted by paul_standeven on Fri, 14/07/2023

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I have a 1 3/32" TT.  I inherited from my father, who got it in a box of ohc Norton stuff in 1954. It was probably fitted to an ohc Norton originally. I had been thinking of putting it on a V-twin project, but its pair is 1 1/8", the size I actually want.  I must have a look at it, can do on Monday.

Paul

Paul, That would be marvellous! Please let me know and maybe we can come to some arrangement?

Kind regards

Bill

Hi Paul,

Did you manage to have a look for the 1 3/32 TT carb? I still cannot find anything on line and am waiting to get to a suitable autojumble.

Kind regards

Bill

Submitted by paul_standeven on Sat, 29/07/2023

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I expected to be able to have a look for it over a week ago, and have not managed it yet, spent all the available time on putting my Dominator back to together and a trip to a machine-shop.  I know exactly where that TT is, I have a box of racing carb parts in a box of Amal stuff.  I hope it will happen next week.

Paul

Submitted by paul_standeven on Tue, 01/08/2023

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and had a look at the two TT bodies.  One is a brass+alloy casting, 1 1/8" bore and stamped as such. The other is an alloy casting, stamped 1 3/32", but measures at 1.15" ie more like a 1 5/32" bore.  It's definitely stamped 1 3/32", but has evidently been over bored.  If my father had realized that it was actually 1 5/32" it would have gone on his 500 alloy Inter.

I think this carburettor is too large for your long-stroke 350 Manx.

Submitted by william_monteith on Sun, 06/08/2023

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Thanks for looking Paul.

I guess that it is back to scouring the autojumbles and hoping for a miracle!

 

Submitted by william_monteith on Sun, 10/09/2023

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Many thanks Dan,

However, I am now sorted. I found one on ebay, in Denmark of all places. £250 later it was mine. I have rejetted it and cleaned it up and it looks the part. All I have to do now is see if it runs! And that will be many months away.

Thanks again.

 



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