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TT carb - the bits I never used

vibrac

Well Known and Active Forum Website User
VOC Member
For some reason lost in the mists of time I always took the choke cable assembly out of my TT, blocked up the cable hole and raced it (Comet) . If on the road I did the hole in the back of the slide to get a good tick over and all was fine.I suppose it was never that cold and I could always give it a good flood.
Now finally I want to fit a choke to my TT, I never throw anything away so I have so far found 2 brass choke tubes and springs, one tube is 1-5/8" long one is 1-1/2" long. when the short one is fitted with the tube and retracted I can still see the bottom say 1/8" of tube in the slot. So before I start cutting springs and tubes or go buying new, does anyone know the correct length of the brass choke tube for an Amal TT 1-1/4" choke (I think 1-3/16 would be the same)
 

Big Sid

Guest
On racing TT s the air slide isn't a choke , it's an mixture control . Does not close off the main throat or choke the motor . It's purpose is to allow a cold start but with maximum power possible , as when the rider starts off in the early morning at the IOM , the air is chilly , as is the cylinder head , thus needing a slightly richer mixture . As the air warms and the race gets serious he can lean things out to the optimum jetting already set earlier after plug readings , tests .
GPs are similar but also having air correction jets or pills beneath a cap on the side of the main body which alters the depression on the jetting selected .
The air slides on street carbs. , originals , Monoblocks , Concentric Mk 1s are indeed actual chokes , blocking off much of the the throat to provide a rich mixture for cold starts . This is a major difference . Totally different equipment and effect . Sid .
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Website Moderator
Here's a question about TT carbs. Do you set the carb up to run correctly when hot with the mixture control in a certain position? I have always assumed with the tube down blocking the air in that part of the carb is for rich when cold and when the motor has warmed up you lift the mixture tube as the rich cold setting is not required.

Only asking as I am getting my Velo Venom clubman back on the road after 20 years and it has a 1-3/16 TT carb on it. The tube on mine is 1-3/8" long and when fully lifted is flush with the top of the slot.

Simon
 

A-BCD

Well Known and Active Forum Website User
VOC Member
I have TT carbs on both my bikes, on the B they are 1 1/8", on the A I have 1 3/16" carbs, both have brass tubes 1" long !!
 

vibrac

Well Known and Active Forum Website User
VOC Member
I think the important remark is "flush with the top of the slot" that would make it 1-3/8 on mine as well
Many thanks vin998
Its all a bit superflous perhaps now that is are no more early morning TT practice :) another piece of racing gone the way of bump starts
 

davidd

Well Known and Active Forum Website User
VOC Member
I was urged to run the tube by Maurice Candy, who is a Vincent owner, but races a Manx which has been national champion many times. I do not have the bike here to measure, but I simply ordered one from Surrey Cycle. I do not use it as a choke, but to adjust the jetting. When I am on the track I adjust it to get maximum thrust and it is very obvious when you hit the sweet spot. I think the Amal literature supports this and says its use is worth half a jet size. Maurice told me it was very handy for dialing in the tuning. It seems to be.

David
 

Big Sid

Guest
More on using TT carbs . My modified street Rapide tan 32mm TT for several years very effectively , modified to idle sweetly and start first prod . Later that bike became the Rattler and they continued to run strong . Later I switched to GP 2s on Big Port heads .
These also behaved themselves and of course ran even faster . Both of these pure racing carbs are superbly made , a joy to use .
Amal were the masters of motorcycle carburetor design , the street types were built down to a very low price while their racing
Equipment was the worlds best . This was accepted around the world . Mukini had to pay Royalties to Amal because they needed to copy Amal design technology to build efficient carbs . Amal owned all the Patents . Sid .
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Vibrac got me worried, I started to think I ran my TT Carb's wrong !! For all those years, I had no choke pipes, My L/ning rep' was never as fast as my Special, It was always a worry. Cheers Bill.
 
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