C V carbs on a commando

Mash · May 31, 2025

Has anyone fitted CV Carbs from a Japanese twin cylinder on a commando with any success? It's something I'm considering so if anyone has any pointers or advice I would like there opinions.

robs ss · May 31, 2025

I'm pretty sure the 1952 (or near) Triumph Thunderbird had SU CV carb(s) fitted. (MC2?)
It was 360 crank so will be relevant.
Not Jap though.

Fast Eddie · May 31, 2025

Mash said:
Has anyone fitted CV Carbs from a Japanese twin cylinder on a commando with any success? It's something I'm considering so if anyone has any pointers or advice I would like there opinions.

Out of curiosity, what is it that you’re aiming to achieve ?

kommando · May 31, 2025

Phoenix an SU carb kit which is a single CV carb.

A sizable increase is MPG at the expense of top speed. You would need a manifold and the space is tight restricting access to the oiling plug for the oil damper on the top of the carb.

baz · May 31, 2025

Mash said:
Has anyone fitted CV Carbs from a Japanese twin cylinder on a commando with any success? It's something I'm considering so if anyone has any pointers or advice I would like there opinions.

Never done twin CVs but I've done a single CV in the past with good results
I've also seen triple set ups on tridents
Also I've seen a triple set up on a BSA rocket 3
The carbs were from a CBR600 with one removed from the bank
What are you planning? Is there enough room?

concours · May 31, 2025

Pretty sure this will be another AI bot having a conversation with you all.

OP, prove me wrong.

Mash · Jun 1, 2025

Thanks for all your replies I have no space constraints as its not in a stock frame. I was thinking of trying some ducati 600 monster carbs .

baz · Jun 1, 2025

Mash said:
Thanks for all your replies I have no space constraints as its not in a stock frame. I was thinking of trying some ducati 600 monster carbs .

Give it a go
Let us know the results

acotrel · Jun 2, 2025

I suggest you end up with the same problem - the shape of the needle. CV carbs compensate for loss of vacuum as you open the throttle. If the mixture richens too quickly, the throttle response is not as good. With the older two-strokes, riders were forced to feed the throttle on. It is a good habit to get into. In road races, some guys struggle around corners and whack the throttle open when the bike is upright. If the throttle fed on in a controlled manner from as far back in the corner as possible - with lean needles, the bike will usually be faster. A CV carb probably will not need as much wrist control to get higher speeds. We should always be able to ride at the limit of tyre grip. So you know where your brain should be ? The slighest sideways movement at the rear tyre contact patch is usually a warning. Always back-off slowly. In fact, if racing, do everything slowly. Situationalist management is dangerous -work up to speed. It usually takes me 5 laps in practice to be fast enough to race.

concours · Jun 2, 2025

acotrel said:
I suggest you end up with the same problem - the shape of the needle. CV carbs compensate for loss of vacuum as you open the throttle. If the mixture richens too quickly, the throttle response is not as good. With the older two-strokes, riders were forced to feed the throttle on. It is a good habit to get into. In road races, some guys struggle around corners and whack the throttle open when the bike is upright. If the throttle fed on in a controlled manner from as far back in the corner as possible - with lean needles, the bike will usually be faster. A CV carb probably will not need as much wrist control to get higher speeds. We should always be able to ride at the limit of tyre grip. So you know where your brain should be ? The slighest sideways movement at the rear tyre contact patch is usually a warning. Always back-off slowly. In fact, if racing, do everything slowly. Situationalist management is dangerous -work up to speed. It usually takes me 5 laps in practice to be fast enough to race.

What about gearing?

C V carbs on a commando

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