Amal 400 Series Carbs

[Horsley-Anarak]

I have been cleaning some spare carbs this evening.

Have noticed that on the ones with adjustment screws, there are two very small holes.

Have not managed to clean these out on one carb, they are very small. I have read that I will need to use a No 78 or 0.016”drill.
These holes are the pilot circuit outlet holes as far as i can make out.

Not sure what they do, would think that it is the idle mixture.

One thing that I think has not been mentioned with the 400 series carbs is the cleaning of the spray tube.

This is the little brass stub that you can see, that sticks up into the throat. The needle passes through it and it atomises the fuel as it enters the air flow.

The spray tube will push out with the main jet removed, and you will see that it has two small holes in it that can become blocked.

Could some of the running problems associated with 400 carbed engines be dirty spray tubes ?

Perhaps it might be worth doing a post on cleaning carbs. It can only improve reliability and running.

With these winter evenings, it would be good maintenance job.

H-A

[Jan]

I use a steel wire from a wire brush to clean the small holes in carbs.

Jan

[Rex NZ]

H-A

Not sure what they do, would think that it is the idle mixture.

One trick I use is to have a squeezy bottle with a pointy nozzle full of turps. I use this to trace/flush carb galleries. Is also a good tell-tale of jet discharge patterns

Rex

[Buzzook]

If H-A or anyone else is willing to do a step-by-step photo sequence and email them to my, I'll do them up into a PDF file so it can be printed off and taken into the shed, or kept handy on the bench....

Have done one such "Beginners Guide" for the "Starting Procedure" but with the Brendan drama it sort of slipped off the immediate radar, and has not yet made it onto the site.

But Charlesuk and I were discussing doing separate ones for each carb, and I've photographed a BIng (as I happened to be cleaning one) so if anyone else would like to "adopt a carb" and register their interest in doing a strip down photo shoot, I'd be happy to do them up into an easy to read and printable "Guide" which we can put up on the site for others to download and print off as required.

Might save all the reinventing the wheel business on the forum...

Any takers???