Amal 1038

tricatcent · Apr 18, 2011

I picked up a big Amal Mk I at the swap meet. I didn't need it, but I liked the look of it. It is 38mm bore. Would it be worthwhile to try this on my 850? Right now I have a single 34mm VM Mikuni and I am satisfied with it.

The Amal would have the advantage of being British, and maybe giving slightly more top end due to the bigger size. Has anyone done this before? Is 38mm too big?

NIgel

pete.v · Apr 18, 2011

If you got it try it. because no two Nortons breath axactly alike, any info you get may be irrelevant.
Anyhow, for what it is worth, you may be reaching the limit of venturi with a 38mm unless you have a larger exhaust (1 1/2 or 1 5/8 big bore).
I had great success with a 36mm VM on my 750 but I am running a 1 1/2" exhaust. Also, I tried a single 34mm Amal Mark2 and it proved to run well but quite weak so you may be in the ball park.
I know I would try it just to see, but i would try anything if I had it in hand.

geo46er · Apr 18, 2011

HI Nigel,
I agree it is probably worth trying the carb out. The only drawback I can see is that you will probably have to invest in a bigger rubber mounting flange, and depending on your manifold the resulting joint may not make for the smoothest transition of air flow. Throttle cable and airfilter may be other considerations.

Peter R · Apr 18, 2011

Make sure your Mk1 Amal is tuned for four stroke use.
Many 1000 series Mk1's are of Spanish origin, and set up for two strokes.
Check if you have the correct jet holder, needle and needle jet and spray tube.

I run a single 34mm Amal mk 2 on my 850 Commando, and must say that the result is a bit disappointing.
Top end power is significantly reduced, on the plus side, the fuel consumption improved quite a bit.
I personally would opt for the twin carb configuration.

Carbonfibre · Apr 19, 2011

If the carb is used than you will need to have it sleeved before use, but its not likely to work as well as a smaller bore VM anyway, as the larger bore size will tend to reduce throttle response at lower speeds.

swooshdave · Apr 19, 2011

Carbonfibre said:
If the carb is used than you will need to have it sleeved before use, but its not likely to work as well as a smaller bore VM anyway, as the larger bore size will tend to reduce throttle response at lower speeds.

Why does it have to be sleeved?

tricatcent · Apr 19, 2011

I talked to a friend of mine who had tried racing a 750 Norton with a single 34 mm Mikunini VM. It didn't give top end power although he said it was great for exiting corners. He changed it to a 40 mm Delorto, and it was very little improvement, so finally he went to the original twin 32mm carbs and the engine had the top end he needed for racing. I guess the restriction is in the manifold not the carb. I think I will try the 1038 anyway. It will look good. It is not likely to big. I was pretty satified with the 34 mm Mikuni anyway. It is brand new. It is British! If I don't like it I can always put the Mikuni back on. Thanks for all your ideas.

I know a hill my bike would climb at 95 miles per hour in third. I will find out if it can go faster with the 1038.

NIgel

swooshdave · Apr 19, 2011

tricatcent said:
I talked to a friend of mine who had tried racing a 750 Norton with a single 34 mm Mikunini VM. It didn't give top end power although he said it was great for exiting corners. He changed it to a 40 mm Delorto, and it was very little improvement, so finally he went to the original twin 32mm carbs and the engine had the top end he needed for racing. I guess the restriction is in the manifold not the carb. I think I will try the 1038 anyway. It will look good. It is not likely to big. I was pretty satified with the 34 mm Mikuni anyway. It is brand new. It is British! If I don't like it I can always put the Mikuni back on. Thanks for all your ideas.

I know a hill my bike would climb at 95 miles per hour in third. I will find out if it can go faster with the 1038.

NIgel

Did you confirm it's not a two stroke carb?

Tim_S · Apr 19, 2011

I used a 38 mm VM on a 74' 850 I had and it ran fine......... I have a 36 mm on a 73' 750 that runs even better ! I'd like to try the twin VM carb setup sometime though to compare. Those of you who have the twin VM's can you tell the difference either way for top end and mpg's?
My MK III with stock 932's gets mid 40's mpg. While the 73' gets low 40's mpg. Seat of pants top end goes to the 750.

Tim_S

swooshdave · Apr 20, 2011

Tim_S said:
Seat of pants top end goes to the 750.

Tim_S

That's the 750 not the carbs doing that, I bet.

Fullauto · Apr 20, 2011

swooshdave said:
Tim_S said:

Seat of pants top end goes to the 750.

Tim_S

Click to expand...

That's the 750 not the carbs doing that, I bet.

Do MK111s have a top end?

swooshdave · Apr 20, 2011

Fullauto said:
swooshdave said:

Tim_S said:

Seat of pants top end goes to the 750.

Tim_S

Click to expand...

That's the 750 not the carbs doing that, I bet.

Click to expand...

Do MK111s have a top end?

Maybe, but everyone else calls it the middle. :mrgreen:

Hobot · Apr 20, 2011

MIght have to diddle cam to get the benefit but I don't know which way. Hope it kicks ass up that steep.

Amal 1038

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