Amal Premier Review

Alan L · May 22, 2025

Hi all,
I thought I would give a review of the Amal Premier carbs I put on my 850 Mk2 Roadster about 6 months ago.
Against the good advice of many on this forum I did not disassemble the units to clean out swarf. The motorcycle started first kick and settled down into a very even idle. They required practically no adjustment.
The motorcycle starts first kick, every kick and is a pleasure to ride. The old carburettors started well and rode ok but it had an incredibly high idle even with the slides fully down and was heavier on fuel than I expected, perhaps just below 50mpg (Imperial)
If anything the new carbs maybe running ever so slightly lean with a very occasional miss if too much throttle is applied at low revs and a little popping in the exhaust on the over-run but it gives extremely good economy (61mpg).
In brief I’m extremely happy with the carburettors, I can’t tell you if I would be equally happy if I had of installed cheaper Wassells.
I don’t know why I persevered with the worn carbs for so long
Alan

acotrel · May 22, 2025

Some people do not know the basics of how their carburetors work. There are three things which are in balance, if the exhaust system and fuel type are not altered - the compression ratio, ignition advance and the jetting. The adjustment for different motorcycles when changing carburetors, is usually in the jetting. Getting the jetting correct requires a systematic approach. I usually start rich then lean off - the problem is to lean off, smaller jets are usually needed. - Then I come back one size. It is difficult to drill a hole in a jet so that it becomes smaller. You cannot predict what size needle jet is needed. So most people probably jet too rich - with a road bike, that does not usually matter.

kommando · May 22, 2025

Alan L said:
If anything the new carbs maybe running ever so slightly lean with a very occasional miss if too much throttle is applied at low revs

Look at the pilots, if they ar 17 then replace with 19's. If they are already 19's then slightly richen the mix at tickover by turning the pilot air mix screws in just a touch.

TRWham · May 22, 2025

I installed new Premiers on my 850 Mk3 about 2 months ago. After some discussion with Greg Marsh, I ordered Pack 137, with 230 main and 19 pilot jets. Before installation, I did disassemble them, but there was no debris and the floats were correct. After running for 2 months, I raised the needles from 2 to 3 early on, but just dropped the mains to 220s as they were a bit rich at WFO but happy below that. The bike has an original airbox with the venturis removed and original style, but replacement, bean can silencers (no balance pipe), so it doesn't need a fire hose supplying fuel.

Alan L · May 22, 2025

kommando said:
Look at the pilots, if they ar 17 then replace with 19's. If they are already 19's then slightly richen the mix at tickover by turning the pilot air mix screws in just a touch.

Hi Kommando, thank you for your advice. Actually the bike is running so well I would be loath to touch it.

YING · May 25, 2025

TRWham said:
I installed new Premiers on my 850 Mk3 about 2 months ago. After some discussion with Greg Marsh, I ordered Pack 137, with 230 main and 19 pilot jets. Before installation, I did disassemble them, but there was no debris and the floats were correct. After running for 2 months, I raised the needles from 2 to 3 early on, but just dropped the mains to 220s as they were a bit rich at WFO but happy below that. The bike has an original airbox with the venturis removed and original style, but replacement, bean can silencers (no balance pipe), so it doesn't need a fire hose supplying fuel.

I think Greg Marsh checks out all the new carbs he sells. I always trust anything I get from him.

TRWham · May 26, 2025

YING said:
I think Greg Marsh checks out all the new carbs he sells. I always trust anything I get from him.

I imagine he does, but I got these direct from Burlen as at that time he had no stock of the carbs I needed.

johnm · May 26, 2025

I will list my experiences but with a very big caveat.

The premier carbs I fitted were purchased about 6 or 7 years ago. So early on in the series. And were definitely NOT the latest aluminium ones.

These days my carbs are working perfectly and have been doing so for about 4 years.

So I found the following in a set from a NZ retailer in a box set for a Mk2 850.

1. The main jets were different sizes, one a 260 and one a 200. So first up check the components are correct for your model both sides.

2. The bike was terriable at coming off idle onto the transition even when fully warm. So changed the 17 pilot jet to 19. This is standard on new ones now.

3. Cleaned swarf from all passages ways.

4. Set the fuel level. One side was way out. The other in spec.

5 Checked and where necessary cleaned up any interference of the bowl gasket and the spindle that secures the float to the float movement.

6 changed the floats to the ones with the rounded tabs and polished off any punching feathered edge on the float needle slot.

7 . Not personally but an engineering friend who does lots of bikes found a couple of bodies that had tappered bores for the throttle slide and therefore poor to nil idle from new due to excess clearance.

After fixing all that the bike starts perfectly on the choke on a cold morning and once warmed up runs perfectly from idle to wide open throttle. All settings as standard except I raised the needle one notch on the left carb only because the plug looked a bit lean. Get 60 miles to UK gallon.

My conclusion on the early Premiers is therefore that quality control was poor but once sorted they are good carbs.

Reading later reports would suggest they have now sorted the quality control out. But I have no personal experience of that.

marshg246 · May 26, 2025

johnm said:
I will list my experiences but with a very big caveat.

The premier carbs I fitted were purchased about 6 or 7 years ago. So early on in the series. And were definitely NOT the latest aluminium ones.

These days my carbs are working perfectly and have been doing so for about 4 years.

So I found the following in a set from a NZ retailer in a box set for a Mk2 850.

1. The main jets were different sizes, one a 260 and one a 200. So first up check the components are correct for your model both sides.

2. The bike was terriable at coming off idle onto the transition even when fully warm. So changed the 17 pilot jet to 19. This is standard on new ones now.

3. Cleaned swarf from all passages ways.

4. Set the fuel level. One side was way out. The other in spec.

5 Checked and where necessary cleaned up any interference of the bowl gasket and the spindle that secures the float to the float movement.

6 changed the floats to the ones with the rounded tabs and polished off any punching feathered edge on the float needle slot.

7 . Not personally but an engineering friend who does lots of bikes found a couple of bodies that had tappered bores for the throttle slide and therefore poor to nil idle from new due to excess clearance.

After fixing all that the bike starts perfectly on the choke on a cold morning and once warmed up runs perfectly from idle to wide open throttle. All settings as standard except I raised the needle one notch on the left carb only because the plug looked a bit lean. Get 60 miles to UK gallon.

My conclusion on the early Premiers is therefore that quality control was poor but once sorted they are good carbs.

Reading later reports would suggest they have now sorted the quality control out. But I have no personal experience of that.

Raising the needle on one carb only, IMHO, is fixing a symptom, not the problem. Each carb has numbers on the side. R932 and L932 and also 2-3 numbers in the same area. Please say those numbers. It's always best to determine if dealer issues or Amal issues are at fault. The carbs may have other issues if not properly matched.

nortonmargie · May 26, 2025

I got Amal Premiers a few years ago. No swarf, but the main jets were very wrong and I was getting 30 miles to the US gallon. Once switched to the right jets (270? need to look up) they have worked very well and the bike actually idles nicely

johnm · May 26, 2025

marshg246 said:
Raising the needle on one carb only, IMHO, is fixing a symptom, not the problem. Each carb has numbers on the side. R932 and L932 and also 2-3 numbers in the same area. Please say those numbers. It's always best to determine if dealer issues or Amal issues are at fault. The carbs may have other issues if not properly matched.

Hi

The noes are R 932 29 and L 932 30

This on an August 1974 Mk2 850 with hamcan filter. Well 80 % of a ham can because I shortened it to fit the CNW starter. As in the photos. Peashooter mufflers. No mutes. Balance pipe. All exhausts and inlet manifold joints checked for leaks. Pazon ignition set to 28 deg advanced on calibrated degree disc. Standard 850 cam installed straightup. 9.25 :1 CR.

I note this carb pack is listed on your site as a 73 74 Mk1 and Mk2 option. You list pairing 35 36 as 1974 Mk2. All settings jetting etc are the same however for both packs

As I said the only alteration from stock settings was raising the needle one notch on the left side. Plugs looked like this left and right.

I'm pretty happy with the way things run at present. I have played with carb tuning a fair bit over the years for a variety of fuels with racing in NZ with a 500 Dommie on Concentric carbs and the Manx GP with AJS 7R and OHC Velos on Gardener carbs using Motec fuel analysers etc.

https://www.motec.com.au/products/category/Lambda%20Measurement

Interested in your thoughts. In the longer term I am planning to put it on an inertia dyno with the Lambda senser but it's in the South island and earliest I'll be down there is our next summer.

Cheers John

marshg246 · May 27, 2025

johnm said:
Hi

The noes are R 932 29 and L 932 30

This on an August 1974 Mk2 850 with hamcan filter. Well 80 % of a ham can because I shortened it to fit the CNW starter. As in the photos. Peashooter mufflers. No mutes. Balance pipe. All exhausts and inlet manifold joints checked for leaks. Pazon ignition set to 28 deg advanced on calibrated degree disc. Standard 850 cam installed straightup. 9.25 :1 CR.

I note this carb pack is listed on your site as a 73 74 Mk1 and Mk2 option. You list pairing 35 36 as 1974 Mk2. All settings jetting etc are the same however for both packs

As I said the only alteration from stock settings was raising the needle one notch on the left side. Plugs looked like this left and right.

I'm pretty happy with the way things run at present. I have played with carb tuning a fair bit over the years for a variety of fuels with racing in NZ with a 500 Dommie on Concentric carbs and the Manx GP with AJS 7R and OHC Velos on Gardener carbs using Motec fuel analysers etc.

https://www.motec.com.au/products/category/Lambda%20Measurement

Interested in your thoughts. In the longer term I am planning to put it on an inertia dyno with the Lambda senser but it's in the South island and earliest I'll be down there is our next summer.

Cheers John

At least you were sold the correct carbs. There is a slight confusion on Amal's part. In one place they list PACK 138 as for Interstate but generally they list if for later 74 MK2. As you noted, PACK 136 is MK1/MK2 but basically 73 - Early 74. Yes, they are actually identical. According to Amal, the needle clip belongs in the bottom slot (full rich). The carb numbers varied on multiple things, but often just the order from the bike manufacturer (new order, new sub-number).

I would verify the carb sync, that the needles are the same, that the needle jets are both 106m and of course, no air leaks. Your plugs look correct to me (assuming E10 gas) but should not with the needle clips in different locations!

johnm · May 27, 2025

marshg246 said:
At least you were sold the correct carbs. There is a slight confusion on Amal's part. In one place they list PACK 138 as for Interstate but generally they list if for later 74 MK2. As you noted, PACK 136 is MK1/MK2 but basically 73 - Early 74. Yes, they are actually identical. According to Amal, the needle clip belongs in the bottom slot (full rich). The carb numbers varied on multiple things, but often just the order from the bike manufacturer (new order, new sub-number).

I would verify the carb sync, that the needles are the same, that the needle jets are both 106m and of course, no air leaks. Your plugs look correct to me (assuming E10 gas) but should not with the needle clips in different locations!

When I found the different main jets I actually had a friend go through all the jets with jet size guages. So they have been measured to be sized correctly as per the Amal markings. I initial thought that 200 vs 260 mains might be a stamping error but no they guaged as different. The needles are also the correct 850 ones. Can't remember the no of grooves off the top of my head but I know I checked. Step spray tube is fitted.

I have a pretty full range of jets from racing days so was able to guage several jets for comparison. Ignore the larger main jets. They are for methanol.

I also spent a lot of time syncing the slide heights and checked with pressure balance guages on the inlet manifolds.

I think the carbs are set up pretty OK. But the left one seems to like that one notch raised needle.

But now I notice you report Amal say needle in the bottom clip ie fully rich position whereas both the Norton workshop manual and Norman White say use the top clip position. Ie lean.

I followed the Norton manual setting the needle in the lean position and then raised it one notch on the left side to richen the lower mid range.

Maybe this is the issue?

johnm · May 27, 2025

johnm said:
When I found the different main jets I actually had a friend go through all the jets with jet size guages. So they have been measured to be sized correctly as per the Amal markings. I initial thought that 200 vs 260 mains might be a stamping error but no they guaged as different. The needles are also the correct 850 ones. Can't remember the no of grooves off the top of my head but I know I checked. Step spray tube is fitted.

I have a pretty full range of jets from racing days so was able to guage several jets for comparison. Ignore the larger main jets. They are for methanol.

I also spent a lot of time syncing the slide heights and checked with pressure guages on the inlet manifolds.

I think the carbs are set up pretty OK. But the left one seems to like that one notch raised needle.

But now I notice you report Amal say needle in the bottom clip ie fully rich position whereas both the Norton workshop manual and Norman White say use the top clip position. Ie lean.

I followed the Norton manual setting the needle in the lean position and then raised it one notch on the left side to richen the lower mid range.

Maybe this is the issue?

Interesting. I checked the Amal site and they do indeed say clip in position 3. Ie lower and therefore richer position.

But every workshop manual I have, Norton, Clymer, and Norman White say top. Ie lean. Which is what I did.

Ah well.

seems to run just fine but interesting.

L.A.B. · May 28, 2025

johnm said:
But now I notice you report Amal say needle in the bottom clip ie fully rich position whereas both the Norton workshop manual and Norman White say use the top clip position. Ie lean.

However, Norton Service Release N3/48 recommended that the needles should be raised to the central clip position.

johnm · May 28, 2025

L.A.B. said:
However, Norton Service Release N3/48 recommended that the needles should be raised to the central clip position.

Excellent. We have a full house.

marshg246 · May 28, 2025

johnm said:
Excellent. We have a full house.

And, of course, 50+ years later, people are usually not running what a 73 850 left the factory with. IMHO, the workshop manual(s), Amal advice, and Service Release are written to a standard. The Service release does not make a distinction between MK1/MK2/MK1A or Roadster/Interstate - it just says "1973 850 c.c. Commando Model". Today, the gas is not even the same.

I start in the middle on all. Then a quick test at 1/2 throttle, twist to 3/4 throttle quickly. If it stumbles, lower the clip (raise the needle). Then a proper throttle chop at 1/2 throttle and check the plugs. Generally, I find that the middle or bottom clip position is correct on E10 gas near sea level.

johnm · May 28, 2025

marshg246 said:
And, of course, 50+ years later, people are usually not running what a 73 850 left the factory with. IMHO, the workshop manual(s), Amal advice, and Service Release are written to a standard. The Service release does not make a distinction between MK1/MK2/MK1A or Roadster/Interstate - it just says "1973 850 c.c. Commando Model". Today, the gas is not even the same.

I start in the middle on all. Then a quick test at 1/2 throttle, twist to 3/4 throttle quickly. If it stumbles, lower the clip (raise the needle). Then a proper throttle chop at 1/2 throttle and check the plugs. Generally, I find that the middle or bottom clip position is correct on E10 gas near sea level.

I use NZ 95 RON pump gas. Ethanol content may vary from nil to 10% depending on brand.

NZ 95 RON is roughly equivalent to the USA 91 index according to US motor fuels websites

Amal Premier Review

Alan L

acotrel

kommando

TRWham

Alan L

YING

Pittsboro,NC

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johnm

marshg246

nortonmargie

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