Carburetor models doubt on MK3

javifoto70

javifoto70

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Oct 20, 2022
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Hello,

I have just starting to analize where to start from to restore my 1975 Commando MK3. The bike is not in OEM condition and it also lacks several parts like calipers, head and taillight, seat, wiring and battery...
I pretend to keep it as original as possible but as 70s cafe racer, as a 70s guy would have accomplish a cafe racer with it.
The seller told me the frame and engine were totally restored, and it looks like.

Revising what I need to work on and what parts I need to find/buy I have an important doubt:
The carburetors are written AMAL 930 and from the OEM specs they should be 932.
Both carburetors look like being Right side!! And only the right one includes the choke lever.

Are they ok and compatible with my bike or should I replace them with 932 ones?
Do I have to find some special part to link both carburetors choke into the same choke lever?

Find here the pictures I made
 

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javifoto70 said:
Revising what I need to work on and what parts I need to find/buy I have an important doubt:
The carburetors are written AMAL 930 and from the OEM specs they should be 932.
Both carburetors look like being Right side!! And only the right one includes the choke lever.
Click to expand...

The carbs are not the correct items. They should be right and left hand (32mm) 932/33 and 932/34.

Those carbs are actually the 1900 series, known as Concentric Mk1.5 or "Spanish" Amals with enrichment plungers instead of slide chokes and never fitted to any standard Commando.

Shop our 1900 Series Range | AMAL Carburetters

Explore our 1900 Series top automotive parts at AMAL Carburetters UK. Upgrade today with quality products for superior performance.
amalcarb.co.uk amalcarb.co.uk
javifoto70 said:
Are they ok and compatible with my bike or should I replace them with 932 ones?
Click to expand...

They're not the correct carbs but it doesn't mean you cannot use them. I assume the previous owner must have done so.
javifoto70 said:
Do I have to find some special part to link both carburetors choke into the same choke lever?
Click to expand...

No, as such a linkage was never fitted as those carbs were never fitted as standard to any Commando.
 
Those carbs are Concentric MK 1.5 & probably came from a Harris Bonneville built between 1985 &1987. The cold start plungers should be fitted with a lever the same as MK 2 Concentrics. Alternatively they can be fitted with a cable kit. If you want to keep these they can be bored out to 32mm. It's easy if you know what you're doing.

Martyn.
 
Thank you for your quick answers!
I would just like to make my bike run well without spending a fortune. The carburetors look in good shape and look like being rebuild.
If I find the "the same as MK 2 Concentrics" to operate the Choke do you think the bike would run ok without boring out to 32mm? (in fact what does it bore out mean?, do I have to machine them or just replace some jets or parts?
And do I have to replace one of them into the LEFT side one?
 
Matchless said:
Those carbs are Concentric MK 1.5 & probably came from a Harris Bonneville built between 1985 &1987.
Click to expand...

Also used on various Spanish trials and other motorcycles such as Montesa, Ossa, Bultaco, Moto-Trans Ducati, etc., etc.

Montesa Ossa Bultaco Sanglas de segunda mano por 240 EUR en Llívia en WALLAPOP

¡Gran oportunidad! Montesa Ossa Bultaco Sanglas de segunda mano por 240 EUR en Llívia. Carburador Amal 930 con starter. Nuevo a estrenar Montesa Ossa Bultaco Ducati Sanglas Derbi Ducson Gimson Vespa
es.wallapop.com es.wallapop.com
 
javifoto70 said:
If I find the "the same as MK 2 Concentrics" to operate the Choke do you think the bike would run ok without boring out to 32mm? (in fact what does it bore out mean?, do I have to machine them or just replace some jets or parts?
Click to expand...

Basically, it means to enlarge the carb bores from 30mm to 32mm.
It is likely they were 2-stroke carbs originally so could have already had changes made to jetting etc. so I suggest you do nothing at this time as the difference in performance between 30mm and 32mm isn't going to be all that much.

javifoto70 said:
And do I have to replace one of them into the LEFT side one?
Click to expand...

You wouldn't necessarily "have to" if the bike runs well enough as it is but it depends on how much money you want to spend.
 
Alright I understand now. I think I will start restoring the complete bike and when the moment will arrive I will make it run and see how these carburetors behave.
Then my only doubt is if I do need to find some part or solution to close the choke on both carburetors because now only the right one can be choked.
 
javifoto70 said:
I think I will start restoring the complete bike...
Click to expand...

In that case, I recommend that you start a thread in the Norton Motorcycle Restorations section..:
www.accessnorton.com

Norton Motorcycle Restorations

Post your Norton Motorcycle Restoration stories here. Post photos and advice. We want to hear how your Norton Restoration is going.
www.accessnorton.com www.accessnorton.com

...and add further posts as you make progress so it's all in one place although, of course, you can also continue to ask any technical questions etc. on the Classic Commando forum.
 
As LAB says it would be best to run the bike with these carbs & see if it suits you. As for boring the out to 32mm, if you decided to go down that route it would mean making a fixture to mount the carbs in the lathe. Then after removing the spray tubes boring the throat of each carb to the desired size, in this case 32mm dia. The 1900 series bodies are common to 28, 30, & 32mm sizes.
 
Those carbs are great, the cold start device works well when set up.

As already suggested, your best way of getting the cold start set up to work would be by converting to cable operation. Last time I looked, Burlen fuel systems had these parts in stock.

They‘re not off of a late T140 though BTW, those versions were the rubber mounted type, rather than the flange fitting type that you have.
 
Matchless said:
Those carbs are Concentric MK 1.5 & probably came from a Harris Bonneville built between 1985 &1987. The cold start plungers should be fitted with a lever the same as MK 2 Concentrics. Alternatively they can be fitted with a cable kit. If you want to keep these they can be bored out to 32mm. It's easy if you know what you're doing.

Martyn.
Click to expand...
Just as easy to bore them to 33mm We are talking cafe racer here right! :p
 
Matchless said:
As LAB says it would be best to run the bike with these carbs & see if it suits you. As for boring the out to 32mm, if you decided to go down that route it would mean making a fixture to mount the carbs in the lathe. Then after removing the spray tubes boring the throat of each carb to the desired size, in this case 32mm dia. The 1900 series bodies are common to 28, 30, & 32mm sizes.
Click to expand...
...or 33mmm, like the works Nortons and most production racers did!
 
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L.A.B. said:
Also used on various Spanish trials and other motorcycles such as Montesa, Ossa, Bultaco, Moto-Trans Ducati, etc., etc.

Montesa Ossa Bultaco Sanglas de segunda mano por 240 EUR en Llívia en WALLAPOP

¡Gran oportunidad! Montesa Ossa Bultaco Sanglas de segunda mano por 240 EUR en Llívia. Carburador Amal 930 con starter. Nuevo a estrenar Montesa Ossa Bultaco Ducati Sanglas Derbi Ducson Gimson Vespa
es.wallapop.com es.wallapop.com
Click to expand...
correct , and this is exactly what my Sherpa 250 has fitted, as FE says starting the engine with it is a dream
 
Though I always save a dollar when I can I know from much experience that old Amals can give you much trouble and aggravation.
I would try to make these work but not try too hard. If they run well consider that you've dodged a bullet. If you try everything and they still won't work then buy a new set of premiers....costly but often times the only solution. Don't bother boring your carbs out. Limit the amount of time and money you spend on your existing carbs.

Very little difference between 30mm and 32mm.

I admit to extreme bias against old Amal carbs.
 
Since I am new on Norton I better follow seattle##gs suggestion. I will try to find the parts to operate cold start through cable (although initially I have no clue where to start looking for them...), then I will start the engine and if the engine works ok I will not mess around. But if I face carburetion troubles then I will just buy the new AMAL 932 Premier set.
My first objective is being able to make the bike run properly and get a good looking and reliable bike. Think that I have start only ordering a kit of Imperial spanners and sockets from UK and I realize that since Brexit the shipping cost is become ridiculous. Once I will get some knowledge and skills on Norton I will be able to follow more advanced cafe racer suggestions... I am looking forward to do it!!
 
javifoto70 said:
Think that I have start only ordering a kit of Imperial spanners and sockets from UK
Click to expand...

You will need various Whitworth/BS and fractional 'AF' (across-flats) size tools.
To do any work on the clutch you will need a clutch spring compressor tool.
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk
Also, a cut-down Allen key/wrench is useful for removing the carb manifolds (with carbs attached).
Carburetor models doubt on MK3
Note that the original manifold cap head screws were 5/16" Whitworth with 7/32" sockets, however, these are often replaced with 5/16" UNC cap heads that have 1/4" sockets.
Carburetor models doubt on MK3

Carburetor models doubt on MK3

Edit: Your carb pictures also show the rectifier (not the standard Mk3 type) and starter solenoid fitted between the engine cradle plates as both would normally be in the battery compartment area.
It also looks like the gearbox spacer washer (43) could be at the wrong (R/H) end of the upper mounting.
andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
 
Last edited:
seattle##gs said:
Though I always save a dollar when I can I know from much experience that old Amals can give you much trouble and aggravation.
I would try to make these work but not try too hard. If they run well consider that you've dodged a bullet. If you try everything and they still won't work then buy a new set of premiers....costly but often times the only solution. Don't bother boring your carbs out. Limit the amount of time and money you spend on your existing carbs.

Very little difference between 30mm and 32mm.

I admit to extreme bias against old Amal carbs.
Click to expand...
I'm not fond of Amals of any age!
 
L.A.B. said:
You will need various Whitworth/BS and fractional 'AF' (across-flats) size tools.
To do any work on the clutch you will need a clutch spring compressor tool.
andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk
Also, a cut-down Allen key/wrench is useful for removing the carb manifolds (with carbs attached).
Carburetor models doubt on MK3
Note that the original manifold cap head screws were 5/16" Whitworth with 7/32" sockets, however, these are often replaced with 5/16" UNC cap heads that have 1/4" sockets.
Carburetor models doubt on MK3

Carburetor models doubt on MK3

Edit: Your carb pictures also show the rectifier (not the standard Mk3 type) and starter solenoid fitted between the engine cradle plates as both would normally be in the battery compartment area.
It also looks like the gearbox spacer washer (43) could be at the wrong (R/H) end of the upper mounting.
andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
Click to expand...
I actually have 2 of each retaining my fabricated steel manifold for twin Mikunis!! (Rickman Frame, vertical mount engine)

Arranged, larger ones inner, smaller ones outer! The manifold tubes splay outward! I use a T bar Allen wrench on the inners, but have to use a cut-down key as shown on the outers!

Whilst technically different thread angles and depth, both screw in easily with fingers and with the same amount of resistance!


Oh! Whilst we are pointing out picky stuff, we should also note that the inlet rocker in the pictures is retained by a bolt.

Whereas, to give the alloy head threading an easier life, it should be the correct stud and a nice special domed nut that fits the correct copper washer!! :eek:
 
Last edited:
My MK1.5 930 carburetors do not have the Tickler pin but only a little open pipe that I do not know whats it is made for, does it mean I do not need to ticker to fuel feed them on cold start?
 
Fast Eddie said:
Those carbs are great, the cold start device works well when set up.

As already suggested, your best way of getting the cold start set up to work would be by converting to cable operation. Last time I looked, Burlen fuel systems had these parts in stock.

They‘re not off of a late T140 though BTW, those versions were the rubber mounted type, rather than the flange fitting type that you have.
Click to expand...
Hi Eddie,

I have not being able to find the cold start kit or parts I need in order to operate both carburators. As you see on my pictures the right hand carburator does include the lever which works properly but, how can I get a similar lever to operate the other carburetor (which unfortunately it is exactly the same right hand model)?
I am considering just buying and installing the very same lever on the left mounted carburator and see if I am able to put my hand between the carburetors to push/pull the new lever.
 
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