I am about to pull and rebuild the MK1 Concentric 930 carb from my 1968 BSA 441 Shooting Star. The bike was always easy to start, one or two kicks but lately it's been getting hard. It's timed correctly and has a new battery and plugs etc but has had to sit without being started for a while a few times so I'm thinking pilot jet etc. Just going to take it all apart, clean, replace with new "stay up float" Aluminumn float needle and gaskets etc. Question is this: I see on Amals site under ( Product Search, / Amal A-Z, they sell Anodized thottle slides or Hard Chromed throttle Slides. I'm thinking (dangerouse) since I'll be there maybe I should replace the slide too. What is better, anodized Alloy or Chromed brass slide??? And this is important. How do I know which one to order for this specific bike?? Thanks. Glenn.

If your carb has not been re-sleeved, you will need to replace the carb body as well, as this will certainly be badly worn after any amount of use. Use of a chromed brass slide in a new carb, will extend the service life a little, but its still not going to be comparable to a Jap carb.

Carbonfibre wrote:If your carb has not been re-sleeved, you will need to replace the carb body as well, as this will certainly be badly worn after any amount of use. Use of a chromed brass slide in a new carb, will extend the service life a little, but its still not going to be comparable to a Jap carb.

Or you could get the new slides and see how it does.

After taking the carb apart you should be able to tell whether there is enough wear to justify a new body or not... the slide will play around an abnormal amount.

I got my chromed brass slides from British Cycle Supply. I don't think they are the ones from Amal, but they are quite well constructed. They also have less play than the pot metal slides they replaced...

Fitting new slides to a worn out carb body is a bit like putting a new chain on worn sprockets. Main reason the Amal carbs wear out so quickly , is due to them being made out of totally unsuitable zinc/lead alloy, that wears fast, and distorts easily due to the poor design of the mounting flange area.

Carbonfibre wrote:Fitting new slides to a worn out carb body is a bit like putting a new chain on worn sprockets. Main reason the Amal carbs wear out so quickly , is due to them being made out of totally unsuitable zinc/lead alloy, that wears fast, and distorts easily due to the poor design of the mounting flange area.

Which is why you use one of the new slides in a different material.

If the body is worn out a new slide, even in a different material won't really do you any good, worn out is worn out. You would really need to replace both the slide and body or have the old slide sleeved and the body bored to match. If the body isn't really worn a new slide may be the ticket.

britbike220 wrote:If the body is worn out a new slide, even in a different material won't really do you any good, worn out is worn out. You would really need to replace both the slide and body or have the old slide sleeved and the body bored to match. If the body isn't really worn a new slide may be the ticket.

He hasn't stated how worn the body or slides are.

I based my comment on all current discussion and as a hint to look into the wear. I've already been through this several times.

Glenn -

Bring it to Applebees tomorrow night; I'd love to hold forth about this and that! LOL.

The fact is, you might get by with just a new slide but then if you don't then a new carb might mean that you'd have an extra slide you don't need, unless you negotiate for credit . . . . .

As for type of slide, I'll always take hard chromed brass over anodized aluminum.

ps - park behind the Chase bank with the Shelby Dodge guys.

xbacksideslider wrote:The fact is, you might get by with just a new slide but then if you don't then a new carb might mean that you'd have an extra slide you don't need, unless you negotiate for credit . . . . .

You can buy just the bare bodies.

I am no expert...

But Bushman is:

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html

Note the discussion on slides...

In my case chrome slides eliminated virtually all play and finally gave me a rock steady idle and one kick bike using Amals.

Cheers,

- HJ

Carbonfibre wrote: totally unsuitable zinc/lead alloy, that wears fast, and distorts easily due to the poor design of the mounting flange area.

Okay, but you have to admit that when the chunks of the worn out slide go through the motor, they don't do much damage...

Greg

Thanks for the invite John, if I can make it I will bring the carb. Still haven't had a chance to take it off the bike but that's easy on the BSA. It's tempting to just buy a new body & slide. I put two new bodies & slides on my first Commando years ago and it ran so smooth and nice after I did so I guess that would be the smart thing to do. Sounds like the general thought on slides is that the chromed one's are the hot ticket? That combined with the stay up float and aluminum float needle and I should be thumping along in serenity.

Can't make it tonight to Applebees.