Refitting 32mm Concentric Carbs Minus Chokes

I am planning on removing the choke mechanisms from my concentrics before refitting them. I have the plugs to screw into the mixing chamber top where the choke cable was fitted originally. Is there anything else I need to do apart from leaving the choke slide, spring, etc out of the throttle slide when refitting the carbs?

Are there any issues with air leaks via the throttle slide that I am not aware of?

Before anyone wants to know why I am removing the chokes - I live in an extremely hot country and have no reason to use the chokes on any of my bikes. Flood the bowl, kick and away you go.

Thanks Don

Just plug the top of the carb holes where the cable go in, its all you have to do, I did mine way back in the late 70s and used the end caps out of BIC pens to plug the holes, no need for chokes in our hot areas, even in cold areas the bike will start without chokes.

Ashley

You may get responses from pro-choke advocates that may tell you that if you don't need a choke your probably running too rich, and, to a degree, they are correct.

I have removed the chokes from all the motorcycles I have owned that were fitted with Amals. My thinking, which may be flawed, is simply that if a motorcycle needs a choke in operation to move off from rest from a cold start that the engine isn't ready to bear a load. I believe that air cooled British motorcycles deserve a warm-up period with no load. I gauge the time to start riding to be when my bare hand isn't comfortable being on the head/barrel and the engine responds to the throttle when the carb(s) are transitioning between the idle circuit and the needle.

The other benefit is that throttle effort is reduced and a carb(s) sans choke won't foul your plugs when it's cable breaks. If you must ride in freezing temperatures then you do need larger jets.

Best.

A high mileage riding mate of mine leaves the choke slides in to add some damping to the rattly Amal slides
He says they last a bit longer with reduced slide wear
In the end he gave up and now uses twin VMS on his t140v
Maybe the vibes are different to a commando motor?

Thanks guys for your comments.

Most helpful.

Cheers Don

thunderbolt said:

I am planning on removing the choke mechanisms from my concentrics before refitting them. I have the plugs to screw into the mixing chamber top where the choke cable was fitted originally. Is there anything else I need to do apart from leaving the choke slide, spring, etc out of the throttle slide when refitting the carbs?

Are there any issues with air leaks via the throttle slide that I am not aware of?

Before anyone wants to know why I am removing the chokes - I live in an extremely hot country and have no reason to use the chokes on any of my bikes. Flood the bowl, kick and away you go.

Thanks Don

Click to expand...

Amal part 4/137A that they call "Screwed Plug" is designed for removing the choke. It replaces the adjuster and blanks the hole. Nothing else is needed other than blocking that hole.

I put a plate on the bottom to make it smooth:



For wear: I always rubber mount the carbs.
They last longer, and stay better in tune.

ludwig said:

I put a plate on the bottom to make it smooth:

For wear: I always rubber mount the carbs.
They last longer, and stay better in tune.

Click to expand...

It looks like the plate height matches the cutaway (or the other side), but not the other hemisphere; I can't tell for the picture, but my depth perception isn't very good. I'd be interested in why you chose this approach?

There is a plate made for Mikunis ( http://www.motocarb.com/ufo-insert.html ) that has the same intention, but is fully flush and contoured to fill in the entire bottom of the slide. The logic makes sense, but you would think that major carb manufactures would have taken this approach directly or under license. I'd like to hear what you think as well as anyone who has had similar ideas.

Do you have any pictures of the rubber mounts you are using?

Best.

RoadScholar said:

.. I'd be interested in why you chose this approach?

There is a plate made for Mikunis ( http://www.motocarb.com/ufo-insert.html ) that has the same intention, but is fully flush and contoured to fill in the entire bottom of the slide..

Click to expand...

Why? your link explains it quite well.
You cant use a fully flush plate because it will hit the carb body at the points marked red:



The plate I use (now) is curved at the engine side.
An easier solution is to epoxy a piece of choke slide , or something similar :

RoadScholar said:

Do you have any pictures of the rubber mounts you are using?

Click to expand...

My carbs are mounted on a common manifold, splayed out and in a slight V, so the slides clear the frame when removed. It makes them one unit. The manifold is internally drilled for balance. I don't use the O-rings. They stay on the manifold their entire life.
I won't go into more detail because it is off-topic, and unlikely anyone will want to copy this.



For rubber, I use automotive radiator hose. Works fine .

Ludwig, did you have to change the jetting very much as is mentioned in the Mikuni related link?

They do make rather remarkable claims. It makes perfect sense to me but I’m struggling with the extent of their claims. Did you find a noticeable difference before / after ?

Fast Eddie said:

Ludwig, did you have to change the jetting very much as is mentioned in the Mikuni related link?

They do make rather remarkable claims. It makes perfect sense to me but I’m struggling with the extent of their claims. Did you find a noticeable difference before /

Click to expand...

ludwig said:

Why? your link explains it quite well.
You cant use a fully flush plate because it will hit the carb body at the points marked red:

The plate I use (now) is curved at the engine side.
An easier solution is to epoxy a piece of choke slide , or something similar :

My carbs are mounted on a common manifold, splayed out and in a slight V, so the slides clear the frame when removed. It makes them one unit. The manifold is internally drilled for balance. I don't use the O-rings. They stay on the manifold their entire life.
I won't go into more detail because it is off-topic, and unlikely anyone will want to copy this.

For rubber, I use automotive radiator hose. Works fine .

Click to expand...

Very informative as ever Ludwig I've seen this done with epoxy resin before but I have always wondered about its real effect ?

ludwig said:

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It will be an unhappy day when one of those screws falls out.

I use slides made for Mark 1.5 Concentrics. They don’t have the big hole for the air slide. And no, I don’t think it makes any difference to performance.

Fast Eddie said:

Ludwig, did you have to change the jetting very much as is mentioned in the Mikuni related link?

They do make rather remarkable claims. It makes perfect sense to me but I’m struggling with the extent of their claims. Did you find a noticeable difference before / after ?

Click to expand...

Yes, they make pretty wild claims.
I claim nothing, except better throttle response.
But then, there are so many variables.

TT : thanks for your concern, but these screws will NOT come loose..

Does the insulating spacer between cyl head and intake manifolds on my 850 have gaskets either side or not?

I could not find any with the parts I disassembled so am thinking maybe there was just some sealant wiped on either side of the spacer instead!!!

Suggestions please? if sealant then which type is best?

Thanks Don

thunderbolt said:

Does the insulating spacer between cyl head and intake manifolds on my 850 have gaskets either side or not?

I could not find any with the parts I disassembled so am thinking maybe there was just some sealant wiped on either side of the spacer instead!!!

Suggestions please? if sealant then which type is best?

Thanks Don

Click to expand...

The spacer / heat insulator has no other gaskets. I use a thin coating of Yamabond on mine.