ET: Engine (Twin) 229/289 Carb Set Up

[Rob H]

Having some issues setting up the carbs, It seems to pick up Ok from idle with the choke on but when it is off it is very hesitant and will only pull away if you open the throttle very slowly bit by bit until the reves pick up and the throttle is more open then it is fine.

To me it seems as if there is a problem with the idle circuit but I have had the carbs dismantled and put in an ultrasonic machine, also run carb cleaner through and compressed air.

Any idea what to check next?,
would the position of the needle height have an effect at very small openings?
what is a good starting point (turns out) for the pilot jet screw?

 

[davidd]

Rob,

Have you done the Greg Brillus mods?

David

 

[Rob H]

No, which are?

 

[davidd]

This is an Amal problem that has existed for decades and it was written about many years ago in an AMC manual. I think Greg did the hard work of figuring out how to address the issue on Vincents:

You will need a pin vise to hold the gauge bit.

David

 

[Rob H]

Ah I see the confusion, good to know on new carbs but the ones I have on the bike are of original vintage.

 

[greg brillus]

Which gasket kits did you use.........The lower one bellow the jet block (green in the pic above) is an important size. I have seen home made ones used where the center was too small and blocking the pilot circuit. This will restrict fuel flow up to and including small throttle openings.

 

[Peter Holmes]

And it will give you starting problems, and then if you manage to start the bike after much swearing and cursing you will have a horrendous backfire on overrun, well mine did anyway. I think I read on this forum, guitar string wire of the correct gauge is also good for dislodging debris etc. from the fine drillings in the jet block, but you will have to very carefully remove the jet block first as Gregg states.

 

[Rob H]

It is the correct gasket and does not block the idle circuit. Bike starts first kick on choke.

Think will dismantle again and ultrasonic but also use a bit of wire, hopefully just some partial blockage.

 

[davidd]

Ah I see the confusion, good to know on new carbs but the ones I have on the bike are of original vintage.

All the Amal 229/289 carbs are built this way, new and old. This mod was originally written about decades before the new carbs were available.

David

 

[greg brillus]

the larger bore type 29 carb's seem more prone to low speed running issues than the smaller type 26 carb's. A couple of other things to look for are the fit of the carb on each manifold stub, make sure there are no air leaks, and also the float level........The large brass cap nut that secures the jet block to the base of the carb body are available in different heights, this has a direct effect on the float level, it might seem obvious but easily overlooked.