I've been pricing up a single carb conversion - using one of my Amal Premiers...

[Bonzo]

...and the parts (without the carb) alone wouldn't give me much change out of £300!

For instance...

Engine

Engine

www.rgmnorton.co.uk

DOUBLE MANIFOLD GASKET

1864 000581 MANIFOLD GASKET

www.rgmnorton.co.uk

CARB HEAT INSULATING WASHER NOMINAL BORE 32MM

062700 HEAT INSULATING WASHER 063458

www.rgmnorton.co.uk

COMMANDO AIR FILTER FRONT PLATE FOR ONE CARB

050001S RGM NORTON 069767

www.rgmnorton.co.uk

MK1 CONCENTRIC THROTTLE NEEDLE 4 STROKE (2 GROOVE)

991036 MK1 CONCENTRIC THROTTLE NEEDLE 4 STROKE 622/124

www.rgmnorton.co.uk

PREMIER MK1 900 SERIES THROTTLE SLIDE 3.5 CUT AWAY

PREMIER MK1 900 SERIES THROTTLE SLIDE 3.5 CUT AWAYTHE LATEST UPGRADE FOR MK1 CARBURETTORS FROM THE AMAL CARBURETTOR COMPANY ARE PRECISION MADE FORGED ALUMINIUM

www.rgmnorton.co.uk

And possibly new cables, as the carb would be centered...

THROTTLE CABLE FOR SINGLE CARB UPTO 1975, 36" OUTER

THROTTLE CABLE RGM NORTON RGM032

www.rgmnorton.co.uk

CHOKE (AIR) CABLE, SINGLE CARB

NM20276 RGM NORTON RGM-5-100

www.rgmnorton.co.uk

I'm not even sure if there's anything else I've missed off.

 

[baz]

...and the parts (without the carb) alone wouldn't give me much change out of £300!

For instance...

Engine

Engine

www.rgmnorton.co.uk

DOUBLE MANIFOLD GASKET

1864 000581 MANIFOLD GASKET

www.rgmnorton.co.uk

CARB HEAT INSULATING WASHER NOMINAL BORE 32MM

062700 HEAT INSULATING WASHER 063458

www.rgmnorton.co.uk

COMMANDO AIR FILTER FRONT PLATE FOR ONE CARB

050001S RGM NORTON 069767

www.rgmnorton.co.uk

MK1 CONCENTRIC THROTTLE NEEDLE 4 STROKE (2 GROOVE)

991036 MK1 CONCENTRIC THROTTLE NEEDLE 4 STROKE 622/124

www.rgmnorton.co.uk

PREMIER MK1 900 SERIES THROTTLE SLIDE 3.5 CUT AWAY

PREMIER MK1 900 SERIES THROTTLE SLIDE 3.5 CUT AWAYTHE LATEST UPGRADE FOR MK1 CARBURETTORS FROM THE AMAL CARBURETTOR COMPANY ARE PRECISION MADE FORGED ALUMINIUM

www.rgmnorton.co.uk

And possibly new cables, as the carb would be centered...

THROTTLE CABLE FOR SINGLE CARB UPTO 1975, 36" OUTER

THROTTLE CABLE RGM NORTON RGM032

www.rgmnorton.co.uk

CHOKE (AIR) CABLE, SINGLE CARB

NM20276 RGM NORTON RGM-5-100

www.rgmnorton.co.uk

I'm not even sure if there's anything else I've missed off.

The only thing you have left out is the reason?
There's been a huge amount of for and against twin and single carbs on here, no doubt you have read it?
There's very often single manifolds etc on eBay if you keep an eye out

 

[robs ss]

Well, if the cost of the exercise doesn't leave you asthmatic, at least your bike will be!

 

[L.A.B.]

Your Premier carbs should already have anodised 3.5 slides. Do you mean a 3.0?

The "2 ID-groove" 622/124 needle is normally used with the flat-topped 622/074 spray tube. Your '850' Premiers should have the stepped 928/107 spray tubes.

 

[Bonzo]

Your Premier carbs should already have anodised 3.5 slides.

You're quite correct Les (I have PACK136)

I went by the info from The Norman White book...



So that's a £35 saving straight away

 

[L.A.B.]

I went by the info from The Norman White book...

"850cc Machines, 1973-4
Needle 4xID grooves 068102, 928-104
Throttle valve, 3... (should be 3.5)
Spray tube 622/074" (should be 928/107).

 

[Fast Eddie]

Like Baz says, many things in life look expensive without understanding the cost / benefit …

Anyway, your list makes this look like quite remarkable value:

cNw Single 34mm Mikuni Carburetor Kit

Remove the hard to work with, original Amals, once and for all A 34mm Mikuni VM carburetor Simple set-up and great performance Easy starting and great idle Takes advantage of the low and mid range torque of the engine Easy installation Easy to dial in and adjust. Service parts are readily...

coloradonortonworks.net

 

[baz]

You're quite correct Les (I have PACK136)

I went by the info from The Norman White book...



So that's a £35 saving straight away

Back in the day I had an 850 mk2a I fitted Norton atlas manifold that I cut and rewelded to the commando angle
I stuck one of the carbs on
Can't remember what jetting I had
I used a standard Amal pancake air filter that I indented the top to clear the frame gusset
It worked really well and was very economical which was the reason at that time for the conversion
It cost me next to nothing at the time

 

[Fast Eddie]

Back in the day I had an 850 mk2a I fitted Norton atlas manifold that I cut and rewelded to the commando angle
I stuck one of the carbs on
Can't remember what jetting I had
I used a standard Amal pancake air filter that I indented the top to clear the frame gusset
It worked really well and was very economical which was the reason at that time for the conversion
It cost me next to nothing at the time

If saving money on fuel is your objective you have to do a LOT of miles annually before it makes any real difference.

I’d guess it would take many years to recoup the cost.

 

[marshg246]

...and the parts (without the carb) alone wouldn't give me much change out of £300!

For instance...

Engine

Engine

www.rgmnorton.co.uk

DOUBLE MANIFOLD GASKET

1864 000581 MANIFOLD GASKET

www.rgmnorton.co.uk

CARB HEAT INSULATING WASHER NOMINAL BORE 32MM

062700 HEAT INSULATING WASHER 063458

www.rgmnorton.co.uk

COMMANDO AIR FILTER FRONT PLATE FOR ONE CARB

050001S RGM NORTON 069767

www.rgmnorton.co.uk

MK1 CONCENTRIC THROTTLE NEEDLE 4 STROKE (2 GROOVE)

991036 MK1 CONCENTRIC THROTTLE NEEDLE 4 STROKE 622/124

www.rgmnorton.co.uk

PREMIER MK1 900 SERIES THROTTLE SLIDE 3.5 CUT AWAY

PREMIER MK1 900 SERIES THROTTLE SLIDE 3.5 CUT AWAYTHE LATEST UPGRADE FOR MK1 CARBURETTORS FROM THE AMAL CARBURETTOR COMPANY ARE PRECISION MADE FORGED ALUMINIUM

www.rgmnorton.co.uk

And possibly new cables, as the carb would be centered...

THROTTLE CABLE FOR SINGLE CARB UPTO 1975, 36" OUTER

THROTTLE CABLE RGM NORTON RGM032

www.rgmnorton.co.uk

CHOKE (AIR) CABLE, SINGLE CARB

NM20276 RGM NORTON RGM-5-100

www.rgmnorton.co.uk

I'm not even sure if there's anything else I've missed off.

There are at least three different twistgrip requirements for inner cable free lengths so you may need a different cable than you selected or a different twistgrip. Also, I hope you read the description of the manifold - sounds pretty bad!

 

[baz]

If saving money on fuel is your objective you have to do a LOT of miles annually before it makes any real difference.

I’d guess it would take many years to recoup the cost.

I'm trying to remember what it was doing to the gallon
I'm thinking it was 65+mpg and twin carb was mid 40s
I was on a meager apprentice wage at that time

 

[Fast Eddie]

I'm trying to remember what it was doing to the gallon
I'm thinking it was 65+mpg and twin carb was mid 40s
I was on a meager apprentice wage at that time

I get that mate, I was really aiming my comment at Bonzo, an older leisure rider looking at dropping a few hundred quid on the job…

 

[marshg246]

After all my years with two or three Amal Concentrics on British bikes the only impetus I would have to change to a single carb would be to get rid of the tickler. I don't mind tickling, but the smell of gasoline bothers me these days.

 

[Onder]

You don't have to tickle until it pours out all over the place. Just until you hear that slight
air escaping sound. At least that works for me.

 

[marshg246]

You don't have to tickle until it pours out all over the place. Just until you hear that slight
air escaping sound. At least that works for me.

For most of my bikes I don't let it pour out - I know the "tickle time". However, that does not stop the smell. Right now, I have 9 bikes in my shop, and it smells of gasoline much more than a gasoline station!

The Amal MkII and Mikuni equipped bikes I work on generally do not smell.

Also, at 73 I couldn't hear the air escape even without a helmet.

 

[Bonzo]

Thanks for the comments folks

I'm not going to throw £300 on a single carb conversion, but the post was more about the 'add ons' that push the cost up to make it less worthwhile option.

 

[Tornado]

My 850 came to me setup with single 932 fitted. It had the standard hamcan air cleaner with a single hole front plate. Ran the bike first couple of seasons like that and did appreciate the simplicity , but now run dual carbs and the bike just goes better. Sorting out balance and tuning took a steep learning curve for me, aided by using a carb balancer (Morgan Carbtune II).
Could not see myself going back to single (though I did fit it again briefly to help troubleshoot one carb against another).
I could be convinced to pop the single setup in a box and send it out to a new caretaker....

 

[acotrel]

Well, if the cost of the exercise doesn't leave you asthmatic, at least your bike will be!

A well-tuned single carb is often better than poorly tuned dual carbs. And with single carbs, there are only one lot of jets. However dual carbs look better - you can delude yourself into thinking you have a real racer.
When Full Auto visited me, his Commando had a single Mikuni. A Mikuni offers a much greater range of jets than an Amal. I really doubt the range of Amal needles is sufficient. I don't use them - only ever Mikuni needles. My Mk2 Amals are really good, but I do not use their needles - it takes almost nothing in that department to make the bike slow.
When you are tuning a motorcycle, you usually start rich, then lean-off. But going down in jet size is not as easy going larger. If you know the size of a hole in a jet, you can use a combination of number and metric drills to make it larger. It is more dificult to drill it smaller. And if you do not drill, how many jets do you need ?

 

[robs ss]

A well-tuned single carb is often better than poorly tuned dual carbs. And with single carbs, there are only one lot of jets. However dual carbs look better - you can delude yourself into thinking you have a real racer.
When Full Auto visited me, his Commando had a single Mikuni. A Mikuni offers a much greater range of jets than an Amal. I really doubt the range of Amal needles is sufficient. I don't use them - only ever Mikuni needles. My Mk2 Amals are really good, but I do not use their needles - it takes almost nothing in that department to make the bike slow.
When you are tuning a motorcycle, you usually start rich, then lean-off. But going down in jet size is not as easy going larger. If you know the size of a hole in a jet, you can use a combination of number and metric drills to make it larger. It is more dificult to drill it smaller. And if you do not drill, how many jets do you need ?

Bonzo's not talking about Mikunis - just a single Amal Premier (30mm?)

 

[Onder]

For a road bike a single carb may well be better all around. Cannot see much difference up to mid range and that is where you spend most of your time. How much time do you spend above 5k?
But I suppose it depends on how you ride and where.