Which carb[s]?

I have read somewhere the SU is a tight fit

The cap on the top of the body is hard to unscrew which is needed to top up the dashpot

and Amal do not do a model for the Commando.

As they were the original fitment they do still make them including the cut flange so they fit properly.

On your current Amals what are you having done to make them compatible with current fuels, the jets are no different but the floats can be changed to suit the fuel better, but they do not even need removing for that change. My old floats are currently fine, fingers crossed.

When doing a rebuild I send mine away for resleeving, the biggest fault with amals is the slide and body wearing themselves out being of the same metal (an engineering no no, what were they thinking).

The SU really suits both the 750 & 850 Nortons. You get easy starting, loads of bottom end grunt and amzing fuel consumption figures. 70mpg plus!!!

The drawbacks that hit me with the SU, on my 750 Commando, were.....having to top up the dashpot every 1000 miles plus it succumbed to both Ethanol and old age. The estimated bill to bring it back to life was a wallet burning £170.

I considered a Mikuni as an alternative but this is £250 for the basic model. All the owners I have met who use this carb on their Nortons recommend buying the choke conversion which adds another £40 to the bill.

I am about to purchase one of the new 32mm Premier Concentrics and see what it is like.

I have the single Mk 1 32mm Amal on my Mk3 850 Commando and it works very well. Fuel consumption increased from a twin Amal 45 mpg to 68 mpg. 3 1/2 slide and 260 main jet. Easy starting too, especially since I changed back to 20/50 oil. I love the lighter throttle action. All discussed in previous threads.

As for Ethanol, best not to use it. Outside of Devon and Cornwall, officially the South West, BP Ultimate is currently E0 but I have a feeling it might go E5 when E 10 is introduced, thanks to the FBHVC.

Sorry read you original question wrong and assumed Amal just make Amals but of course Burlen the owners also make SU's, they will make the SU but not the manifold which is the important bit.

Unconfirmed I have the spec as

CarbHIF6

Needle BFD SUNZX8052, the spring as red SUAUC4387

Previously phil_hannam wrote:

The SU really suits both the 750 & 850 Nortons. You get easy starting, loads of bottom end grunt and amzing fuel consumption figures. 70mpg plus!!!

The drawbacks that hit me with the SU, on my 750 Commando, were.....having to top up the dashpot every 1000 miles plus it succumbed to both Ethanol and old age. The estimated bill to bring it back to life was a wallet burning £170.

I considered a Mikuni as an alternative but this is £250 for the basic model. All the owners I have met who use this carb on their Nortons recommend buying the choke conversion which adds another £40 to the bill.

I am about to purchase one of the new 32mm Premier Concentrics and see what it is like.

phil...i agree with you about the su..i,ve used a su on my 850 for 15yrs and its been fine.even filling the dashpot i found not a problem with the black cap unscrewed i could just bend a plastic wesco type oil can nossle and squirt in the oil...the only trouble i had in 15yrs was replacing the original air filter foam which had fell apart for a [k and n] type filter ..this gave me trouble as it starved the engine of air it would run fine for a while then suddenly dies.i made a replacement from foam then all was ok//i,ve now fitted a mikuni[bought from the states about 10yrs ago when the pound worth $193 it worked out at £140.so i,ve just fitted it.getting about 65per gal slightly less than the su /i also think the mikuni looks better /allens recommend a 30 pilot jet but the bike is sometimes hesitant to pick up when at small throttle openings.// i may go for a bigger pilot jet...i,ve also opted for the handlebar choke setup so i can adjust it as it warms up...the standard choke setup is a lever on the carb [70s jap style]and the engine hunts on full choke and sometimes dies on the overrun if turned off before warm.so i changed it..its nearly always starts first kick.the su was second or third kick. a know some owners have gone for the rgm mk2 setup and its a cheaper option and they say its not to bad..

i hope this imput is of some help to someone..

There was a picture on the carousel at the top of the home page in recent months. It was a close -up of a Commando fitted with what looked like a Weber or Del-orto twin choke carb. Not heard of anyone making any observations on this, but it did look very neat I thought.

Perhaps the owner can enlighten us.

John Holmes, I phoned Amal and they say they do not do an SU for the Commando.

Burlen make SU carbs, they do not list one for Commando's but use theinformation (but confirm it first)I have posted and order one to the spec, throat size should be 1.5". All you need then is the manifold. Alternatively buy a second hand one off ebay and jet to suit.

Phoenix engineering at Halfpenny green developed the single SU carb conversion for the Commando. Bernard Hooper was at the very start of Commando develpment and had his own company developing stepped piston 2 stroke engines as per the Norton Wulf. These engines are made in various configurations for the drone industry, but that as they say, is another story. Bernard Hooper passed away a few years ago and the company is run by his Son Peter now.

The manifold is very short and the carb works well though I thought mine was bigger than 1.5" I got rid of mine due to poor starting. (the carb works on a Constant Vacuum principal which is great if you have an electric start but a kickstart without a head of fuel is frustrating. I've subsequently heard of a priming device for SUs used by the Harley Davidson fraternity.

It is worth taking a look at Jim Schmidts flatslide carb kit from the States, works out cheaper than a new pair of Amals and includes manifolds and filters but, and here's the rub, you have to pay import duty unless you just happen to be in the States on holiday and a pair should just find their way into your baggage. You know the score, one manifold in your wifes handbag, carb in her suitcase, another manifold in your suitcase and the other carb in your carry on baggage, (tell them it's an inhaler for your asthma!.........well it is isn't it?)

Further to my last, a twin choke weber will fit but you will have to cut away the frame web and there are some single Kehein pumper flatslide cabs up to 40mm getting rave reviews on the Access Norton website. Again chopping the frame is in order here.

With 60% of the 60,000 Commandos made, going to the States, that's where a lot of good gen is available.

My 1971 750 came back from Norman White a few weeks ago with a single Mikuni to replace the worn original Amals, which weren't fixed by my fitting new slides and springs a while ago. Is not for me to question Norman's judgement.

Previously david_evans wrote:

Phoenix engineering at Halfpenny green developed the single SU carb conversion for the Commando. Bernard Hooper was at the very start of Commando develpment and had his own company developing stepped piston 2 stroke engines as per the Norton Wulf. These engines are made in various configurations for the drone industry, but that as they say, is another story. Bernard Hooper passed away a few years ago and the company is run by his Son Peter now.

The manifold is very short and the carb works well though I thought mine was bigger than 1.5" I got rid of mine due to poor starting. (the carb works on a Constant Vacuum principal which is great if you have an electric start but a kickstart without a head of fuel is frustrating. I've subsequently heard of a priming device for SUs used by the Harley Davidson fraternity.

It is worth taking a look at Jim Schmidts flatslide carb kit from the States, works out cheaper than a new pair of Amals and includes manifolds and filters but, and here's the rub, you have to pay import duty unless you just happen to be in the States on holiday and a pair should just find their way into your baggage. You know the score, one manifold in your wifes handbag, carb in her suitcase, another manifold in your suitcase and the other carb in your carry on baggage, (tell them it's an inhaler for your asthma!.........well it is isn't it?)

I recently had a phoenix SU kit reconditioned by Burlen.... NOT cheap, but returned maybe better than new? Starts well (by foot!), progressive choke action, no priming......

Tried the Mikuni but couldn't live with the choke on/choke off setup. Might be fine if you've plenty of time to warm up, but it did lead to frustration and embarassment in stop/start traffic when not fully warm. The SU handles it all no problem.

just fitted single Mikuni conversion to my 850 and can honestly say it has transformed the bike (may be my carbs where worn) kicks first time hot or cold!.

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So does my Mk3 850 with a single 932 Mk 1 Amal, since I changed oil from SAE 40 to 20/50.