Older Amal 930"s

jms · Friday at 3:33 PM

So several years ago when I started to restore my Dunstall Atlas it came with Amal Concentric 930 carbs. They are not Premiers. I really have no idea how old they were but decided to give them a try. The bodies looked ok as did the slides. Fast forward to build completion the bike starts easily every time but when I sync the cards with my Carbmate I can get the motor to idle down around 1000 rpm but the idle is erratic. Now I'm no expert on Amals and have a lot more experience tuning Dellorto's and Bings but I'm guessing it's because they are worn. I wouldn't think that new slides in a worn bore would be money well spent either. Man those Premiers are expensive!

Matchless · Friday at 4:08 PM

Reassuringly expensive I would suggest. The Premiers are excellent & worth every penny. I've fitted several sets now, & if Amal had made them this well in the first place Brit bikes would have run better for longer. In the end I guess they just made what BSA/Triumph & Norton Villiers would pay for.

hybridracer · Friday at 4:46 PM

jms said:
So several years ago when I started to restore my Dunstall Atlas it came with Amal Concentric 930 carbs. They are not Premiers. I really have no idea how old they were but decided to give them a try. The bodies looked ok as did the slides. Fast forward to build completion the bike starts easily every time but when I sync the cards with my Carbmate I can get the motor to idle down around 1000 rpm but the idle is erratic. Now I'm no expert on Amals and have a lot more experience tuning Dellorto's and Bings but I'm guessing it's because they are worn. I wouldn't think that new slides in a worn bore would be money well spent either. Man those Premiers are expensive!

You've got a Dunstall Atlas, why are you worrying about an erratic idle?

jms · Friday at 4:49 PM

Documented! Good point

Junglebiker · Sunday at 7:43 PM

Matchless said:
Reassuringly expensive I would suggest. The Premiers are excellent & worth every penny. I've fitted several sets now, & if Amal had made them this well in the first place Brit bikes would have run better for longer. In the end I guess they just made what BSA/Triumph & Norton Villiers would pay for.

I agree, I have a NIB Amal 930 from the late 1960's and it is not very impressive looking. Pics I have seen of modern ones look much better.

mdt-son · Monday at 4:12 AM

jms said:
So several years ago when I started to restore my Dunstall Atlas it came with Amal Concentric 930 carbs. They are not Premiers. I really have no idea how old they were but decided to give them a try. The bodies looked ok as did the slides. Fast forward to build completion the bike starts easily every time but when I sync the cards with my Carbmate I can get the motor to idle down around 1000 rpm but the idle is erratic. Now I'm no expert on Amals and have a lot more experience tuning Dellorto's and Bings but I'm guessing it's because they are worn. I wouldn't think that new slides in a worn bore would be money well spent either. Man those Premiers are expensive!

Sleeving your old carbs is a cheaper option and at least as good as a new set of carbs, IMO. You should fit new needles and jets additionally.

Thread 'Sleeving Concentrics?'

Apr 8, 2026

Does anyone machine worn Amal Concentrics and install sleeved slides? Bruce Chessell has stopped doing them

- Knut

Fast Eddie · Monday at 4:47 AM

The main downside to sleeved original Amals vs new premiers is you don’t get the new removable / cleanable pilot set up.

You also gotta added up the total cost of all new internals and the re sleeving work… might not be quite the saving over new that it first seems.

mdt-son · Monday at 5:26 AM

Fast Eddie said:
The main downside to sleeved original Amals vs new premiers is you don’t get the new removable / cleanable pilot set up.

You also gotta added up the total cost of all new internals and the re sleeving work… might not be quite the saving over new that it first seems.

That's right. However, the cleanable pilot jet set up can be retrofitted if deemed necessary.
Total cost is typically US$ 180 vs. 500 per carburettor, so it's a worthwhile consideration.

- Knut

jms · Monday at 6:24 AM

mdt-son said:
That's right. However, the cleanable pilot jet set up can be retrofitted if deemed necessary.
Total cost is typically US$ 180 vs. 500 per carburettor, so it's a worthwhile consideration.

- Knut

Look what I started!

A lot to think about here!

EstuaryBoy · Monday at 7:38 AM

I'm not normally one for: 'Hang the expense, just throw money at it!', but did 'invest' in premiers this time round. Once dialled in (my 'matched' float heights were anything but!), they're shaping up to be a: 'Fit and forget' solution...

Fast Eddie · Monday at 7:55 AM

mdt-son said:
That's right. However, the cleanable pilot jet set up can be retrofitted if deemed necessary.
Total cost is typically US$ 180 vs. 500 per carburettor, so it's a worthwhile consideration.

- Knut

For those who have the required machining skills and abilities, it’s one thing. For those that don’t, it’s quite another. You won’t get the body boring AND slide sleeving AND pilot mods AND all new internal parts for $180 per carb if paying for all the machining work!

You’re looking at approx $150 in parts for a pair of rebuild kits and new Premier type pilot screws / jets (plus VAT where applicable and shipping).

A pair of Premieres is approx $570 from AN currently (plus VAT where applicable and shipping).

So, sleeving and modifying will more than likely be cheaper, but by how much will depend on machining costs and IMO might not be as much as first thought. Folk should therefore do a proper ‘apples for apples’ cost comparison before deciding.

Matchless · Monday at 9:33 AM

I not only have the skills & machinery, but have also done the job on several sets of Amals. Now that Burlen make new high quality carbs I simply wouldn't waste my time.

mdt-son · Monday at 10:07 AM

Fast Eddie said:
For those who have the required machining skills and abilities, it’s one thing. For those that don’t, it’s quite another. You won’t get the body boring AND slide sleeving AND pilot mods AND all new internal parts for $180 per carb if paying for all the machining work!

You’re looking at approx $150 in parts for a pair of rebuild kits and new Premier type pilot screws / jets (plus VAT where applicable and shipping).

A pair of Premieres is approx $570 from AN currently (plus VAT where applicable and shipping).

So, sleeving and modifying will more than likely be cheaper, but by how much will depend on machining costs and IMO might not be as much as first thought. Folk should therefore do a proper ‘apples for apples’ cost comparison before deciding.

Agreed, and I appreciate the endorsement of Concentric Premieres, but:

1. A pair of Premieres is approx $1000 in the US.
2. 2 x rebuild kit is $110 (price with Burlen). Our good friend marshg246 may supply kits in the US at a favourable price, I think.
3. The price of approx. $180 per carb included remote machining service. It did not include the pilot mod though, which isn't strictly necessary. It's about a restitution to better-than-new state.

- Knut

Fast Eddie · Monday at 11:44 AM

mdt-son said:
Agreed, and I appreciate the endorsement of Concentric Premieres, but:

1. A pair of Premieres is approx $1000 in the US.
2. 2 x rebuild kit is $110 (price with Burlen). Our good friend marshg246 may supply kits in the US at a favourable price, I think.
3. The price of approx. $180 per carb included remote machining service. It did not include the pilot mod though, which isn't strictly necessary. It's about a restitution to better-than-new state.

- Knut

I disagree, if you want to really compare costs vs benefit you need to compare the costs of converting to full Premier spec. ESPECIALLY considering your claim that sleeved carbs are ‘at least as good’ as new ones.

Even then you’re still using 50 year old monkey metal bodies vs new alloy ones !

But, you pays your money and makes your choice.

Matchless · Monday at 12:00 PM

Another way to look at this, is if we don't buy new parts now & again, the companies we rely on will just close down.

jms · Monday at 12:35 PM

Matchless said:
Another way to look at this, is if we don't buy new parts now & again, the companies we rely on will just close down.

Here in the States the actual number for a pair of 930’s is actually $699.00 plus applicable sales tax which varies by State but on avarage is about another $50.Dealing with and coordinating all of the individual parts and machining labor doesn’t seem to make sense if you consider your time and then may not be quite as good in the long run

o0norton0o · Monday at 2:48 PM

I have 40,000 miles on my sleeved 930's. I modify them by drilling and tapping them for clean out port behind the idle jet, so they are just as each to clean as the premiers. You still have to take them off the bike to get to the back side of each carb.
Concentrics have a lifespan. A cylinder going up and down inside a tube with a strong vacuum pulse pulling and releasing thousands of times per minute really grinds away at the back of the carb body. If you vary your throttle a lot you might still have a smooth movement instead of a bump (ask me how I know

), but of course they give you a more lean mixture as they wear. The compensation is that the needle jet wears along with the carb body and makes the mixture more rich, so hopefully there's some canceling out of the effect...
Last year, I got a set of 932's from someone who switched to premiers, so maybe at some point I'll try those out. I do have a '70 model that came with 930's, Does that mean the ports on my head are smaller than the ports on the head of models that came with 932's?? Anyone???

hybridracer · Monday at 3:01 PM

o0norton0o said:
I have 40,000 miles on my sleeved 930's. I modify them by drilling and tapping them for clean out port behind the idle jet, so they are just as each to clean as the premiers. You still have to take them off the bike to get to the back side of each carb.
Concentrics have a lifespan. A cylinder going up and down inside a tube with a strong vacuum pulse pulling and releasing thousands of times per minute really grinds away at the back of the carb body. If you vary your throttle a lot you might still have a smooth movement instead of a bump (ask me how I know ), but of course they give you a more lean mixture as they wear. The compensation is that the needle jet wears along with the carb body and makes the mixture more rich, so hopefully there's some canceling out of the effect...
Last year, I got a set of 932's from someone who switched to premiers, so maybe at some point I'll try those out. I do have a '70 model that came with 930's, Does that mean the ports on my head are smaller than the ports on the head of models that came with 932's?? Anyone???

Your inlet ports are 1 1/8” ( 28.5 mm). Later heads for 932 carbs have 1 3/16” ( 30 mm ) or 1 1/4” ( 32 mm ) ports at the manifold face.

mdt-son · Monday at 7:34 PM

jms said:
Here in the States the actual number for a pair of 930’s is actually $699.00 plus applicable sales tax which varies by State but on avarage is about another $50.Dealing with and coordinating all of the individual parts and machining labor doesn’t seem to make sense if you consider your time and then may not be quite as good in the long run

I'd be interested to know who sells genuine Burlen carbs this cheap? Current price with the Bonneville shop is $1050 for the pair (932's jetted for the Commando).

- Knut

Fast Eddie · 2026-09-08T00:10:28-0600

o0norton0o said:
I have 40,000 miles on my sleeved 930's. I modify them by drilling and tapping them for clean out port behind the idle jet, so they are just as each to clean as the premiers. You still have to take them off the bike to get to the back side of each carb.
Concentrics have a lifespan. A cylinder going up and down inside a tube with a strong vacuum pulse pulling and releasing thousands of times per minute really grinds away at the back of the carb body. If you vary your throttle a lot you might still have a smooth movement instead of a bump (ask me how I know ), but of course they give you a more lean mixture as they wear. The compensation is that the needle jet wears along with the carb body and makes the mixture more rich, so hopefully there's some canceling out of the effect...
Last year, I got a set of 932's from someone who switched to premiers, so maybe at some point I'll try those out. I do have a '70 model that came with 930's, Does that mean the ports on my head are smaller than the ports on the head of models that came with 932's?? Anyone???

All depends which heads you have, assuming they haven’t been messed with.

Older Amal 930"s

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