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Dave

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Is this BINKS carb correct (ish) for my Douglas 2-3/4? Looking for AMAC slide...

Started by Tim OConnor, 16 Oct 2022 at 13:53

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Tim OConnor

Wow, what a difference a good working carb makes! I bought this spare carburetor off of eBay listed as a rare carburetor for 1920s Douglas's such as the 1923 model TS 2 3/4.

I rigged it up as a temporary fitting and boy it makes the engine sing!

This tells me there's definitely something wrong with my current carburetor (AMAC), it is only giving me 1/4 of this power.

Can the BINKS be considered "correct" W-20 or just the AMAC?

The AMAC ticks over fine, starts easy but if I do anything more than crack the throttle it dies. I have tried jets of all sizes with little difference, the float hight is apparently correct, no detectable air leaks. I am ASSUMING that my throttle slide is too loose and letting air by.

Does anyone know of a source for a AMAC T-25E throttle slide or would be willing to sell one?

Thanks!

1920 2 3/4 W-20

EW-Ron

If it had horns, red eyes and 7 toes on each foot it would be 'correct' for something 100+ years old. ?
ESPECIALLY since it makes it run ....
The proof will be if you can ride it thusly, but its sounding hopeful.

Perhaps though it needs some nickel, so it looks less brass era ?

P.S. Have you tried reducing the air when you tried the old carb to get it to rev.
The levers have to be worked together, to some extent, the mixture control was by no means automatic
Giving it full air from low revs may not be how it likes to operate ?

Hutch

Hi Tim,

Good that the replacement carburettor got the bike running as it should and does seem to indicate that the issue is with the Amac carby.

I had a quick look back through your original post on this

https://www.douglasmotorcycles.net/index.php?topic=9264.0

and measured the 7 holes in the sprayer on mine and they come out as the same more or less the same diameter as Jonathon Hewitt posted in reply #7 at approx. 0.98mm.

One item I didn't see you comment on, but I may have missed it, is the fuel path from the bottom of the float bowl to the jet partially blocked? Might pay to check the hole through the float bowl to the banjo fitting and then the jet holder itself? If partially blocked this may let enough fuel through for starting and idling but not enough when the engine is revved? i.e. it would be acting as it has too small a jet in it.

Hope you mange to sort it out but at least now you have a running bike!

cheers

Hutch

Tim OConnor

Quote from: EW-Ron on 17 Oct 2022 at 02:28
P.S. Have you tried reducing the air when you tried the old carb to get it to rev.
The levers have to be worked together, to some extent, the mixture control was by no means automatic
Giving it full air from low revs may not be how it likes to operate ?

With the AMAC carb on the bike will start easily and RPM will increase with the mixture until about 3/4. With or without the mixture open the throttle will stall the engine past more than a slight opening.
1920 2 3/4 W-20

Tim OConnor

Quote from: Hutch on 17 Oct 2022 at 04:11

One item I didn't see you comment on, but I may have missed it, is the fuel path from the bottom of the float bowl to the jet partially blocked? Might pay to check the hole through the float bowl to the banjo fitting and then the jet holder itself? If partially blocked this may let enough fuel through for starting and idling but not enough when the engine is revved? i.e. it would be acting as it has too small a jet in it.

Hope you mange to sort it out but at least now you have a running bike!

cheers

Hutch

thank you!

I have cleaned the bowl but I did not run anything like a wire through the passageway. I will give it a check. thank you!

1920 2 3/4 W-20