Single carb for an 850 Commando ?

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Dec 26, 2008
Hi, has anyone had experience with a single carb on an 850 Commando e.g. a Mikuni as am thinking if changing from the twin mk 1 Amals ?.
Welcome Arctura,

If you enter the word Mikuni into the search facility, then you should find lots of information?
I have a MK 2 Amal on my 850. While I can say it ran perfectly when it was new, I find I have to fiddle with it more as it gets older (or is it me that's getting older??) If I had to do it over, I would use a Mikuni. For one thing, the Amal leaked from somewhere because it became progressively dirtier as years went by, OTOH, the Mikunis on my RD400 (1977) are cleaner than the Amal which is about 20 years younger.

Alternative single carb

Hi Arctura,
Take the time to read the carb thread at Click "Technical" then click "Commando", you have to be a member to access all the info, but, there is quite a bit of carb info available to all. The thread contains several pro and con points of view for various set ups, but, basically tells you that it make take time and carefull sorting for any type of carb to work propperly. Personally, I got a single manifold off Ebay (also available through Map Cycles) and presently run one of the original Amals. It works very good, but, I also have an old Mikuni that I will try next summer just to satisfy my curiousity. Whatever carb you end up with I have no problem recommending a single carb set up. It gives me all the carburetion I need and simplifies the tuning procedure.

single carb

I went through this carb business this year. Got a mk 2 amal and a manifold kit. The bike runs well now, starts first time and I am happy with it. The downsides were the carb quality, poor straight out of the box (spanish made Amal) but the suppliers were very helpful (RGM) even if my patience and ability were stretched! I did speak to other specialists who put me off the mikuni idea as they are very expensive and, I am told, the UK doesn't have a great supply of them.
If i were doing it again i would go for a Mk 1 as they are so easy to work on, and you have 2 already!
This site has the answers, there were replies warning of the poor quality, but as with most things, if you ask ten people there pinion, you get eleven answers so it's down to personal choice, who and where you can get spares from and the the big one for me, who gives you the best backup and support.
i spoke to mick Hemmings and Norvil (can't remember which one said it) but was advised that the way to go was an amal, as the mikuni carbs are built for lawnmowers! Anyway, searching on the internet didn't turn up the required mikuni set up and the Amal option was so much cheaper. At the time I couldn't decide whether to keep the bike or not, and the Mikuni was too expensive an option if i were to sell the bike.
I was looking for easier starting and running, not performance as my modern 955 Triumph fulfills my need for speed!

My main point was the poor quality of the Amal as supplied from the box, but I may have been unlucky, and that it took me a while to decide what to do as everyone I seemed to talk to had their own idea on what is best. Replacement twin mk 1s might have been better as the change in carb caused all sorts of disasters (all self inflicted) and I ended up rewiring the beast, and replaceing the RITA with a Pazon.
Just had a look at teh link provided by LAB and the kit price looks good. I am sure when I searched these out it was nearer £400! I would have gone for a japanese carb otherwise.
Still, live and learn.
Last point LAB, i was in Swafham last Christmas and a roadster was parked up in the high street, not yours was it?
I am in North Essex and have a mk 3 roadster n black and gold.
Mikuni single carb.

Changed from mk1 amals to single Mikuni 36mm vm carb about 3years ago and find its the best thing i have done.
The amals were always having to be kept in check , living in the uk and working Mon to Fri I only had the weekends to spend time with the bike and sort any problems out , however when I fitted the Mikuni I had to eventually change the pilot and main jet to smaller ones as the bike was running rich, easy job to sort, now the bike is fine and I have no complaint at all.

mcmarvelous said:
Last point LAB, i was in Swafham last Christmas and a roadster was parked up in the high street, not yours was it?
I am in North Essex and have a mk 3 roadster n black and gold.

I do own a Black & Gold MkIII Roadster, but no, it couldn't have been mine you saw parked in Swaffham.
I'm over on the Eastern side of Norfolk.
Ah the dark side! i have relatives there as well.

Joke for you

bloke stumbles into the Post office, covered in dust, torn shirt, bits of stick and grass in his beard and with a wild look in his eyes.

The postmaster looks up and says 'ere, you look like Bin Laden'

and the man replies

'No, bin Swafham!'

Bit of a joke for us 'locals....

Have a Happy New Year and i'll get the trusty steed out and about. PS one of my whippersnapper customers said to me the other day, 95% of Nortons are still on the road, the 5% got back home.
Should have banned him.....
Arctura said:
Hi, has anyone had experience with a single carb on an 850 Commando e.g. a Mikuni as am thinking if changing from the twin mk 1 Amals ?.

Single Mikuni is a great upgrade for the Commando. I switched my Amals out three years ago and the bike has run like a top ever since! I think the only major issue is whether or not you want you bike to remain stock and whether you want a Japanese carb on it. Such things matter to some.
I too have a MK2 Amal (Spain), no quality issues...purchased from Old Britts
Single carb for an 850 Commando ?

Here's a Pic of mine installed...Pic taken after draining gas and winterizing.

I have a Mk2 amal on my wifes Mk3 roadster, the complete 34mm kit from RGM. Whilst it generally runs well, now I have fitted a much smaller main jet than supplied, & has never leaked, the idle is far too rich, even with the smallest pilot jet available.
I've just removed the carb this afternoon to investigate the pilot air circuit for blockage etc.

What jets etc are in yours?

When I spoke to Burlen, (very helpful), they sugested the basic problem is that the 34mm carb is too large, should have gone for 32 or 30.

Any info would be very much appreciated.


Hi there, and merry New Year to you old chaps.....
Got a single amal mk2 32mm with manifold on my shelf and want to drop it on a friends 750 Cdo , has anyone got the jetting far as I had been into it had 300 main , 3 throttle slide and 2A i (L?) needle jet ...if not I will buy Panics victory book , a pity cause I had bought Mikuni's victory library book and though pretty good book it's useless for this case. No snow here but may be tomorrow (it happens once every three years........).
Yes me too, the best thing I have done on my commando

Map cycle a good way to purchase aSudco kit with pre-jetted carb
a"kid" game
broken link removed

ollbritts too
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