Single Mikuni or Amal Mk II

I´m going for a single carb on my 850, are there any obvious reason to choose one or the other of the above? Thinking 34mm....standard engine btw.
Tommy

Why single carb? To me, putting a single carb on a Commando is like castrating a fine bull.

The single Mikuni is lower maintenance. Correct jetting May be an issue since the as supplied isn’t quite right. For reference Ken Armani in San Jose has the perfect jet set recommendation for both 750 and 850 Commandos.
Down side to single Mikuni is you cannot use the stock air cleaner and if your 850 is pre MkIII you will need to figure out where to put the ignition switch bracket. I tried a Mikuni on my ‘72 combat for a brief time then returned to the 932 Amals. It had a really strange idle lope that sounded like a Harley idle as well as the other issues above.

the 34 mik does hava bit of a different sound at idle, but it runs just fine and the the right jetting is posted here.. just search them out what is your elevation above sea level?

You can run either single or dual Mikunis with the air cleaner backplate still on so you don't have to move the ignition key. I tried both of these setups back in the late 70s but the stock twin Amals gave a better combination of power everywhere.

If you do convert and decide to use the cable kit for the choke, remember that the choke lever will operate backwards.

I'd put the money towards fixing up the existing Amals or getting the new Premiers.

right below my post is the March 16, 2018 thread on the single Mikuni V twin Amals actual real world Cycle World magazine road test. In short, the report says the single Mikuni idles like a rock and is stronger, the bike is faster, pulls away from a well sorted out twin Amal setup form 50-80 in top gear. It is only in the quarter mile that the twin Amal set up is 4 tenths of a second quicker. The Mikuni 34 has been fitted to Commando for over 40 years now and is very well known, comes correctly jetted from just about every vender, has an excellent choke for one kick starting, and is Cycle World's preferred choice.

I ran my 850 with a single mikuni 34 for 30 years and then out of curiosity bought a new set of Amal Premiers two year ago
to try them out, had them on the bike for one year and went back to the Mikuni a year ago, believing starting, idling, and stronger motor up to 80mph is right for me, I don't ever take it up over 85-90 anymore, just don't care to.

The original question is whether to use one Mikuni or one Amal MK2. The Mikuni is an excellent carburetor. My experience with Amal MK2 is minimal and all bad. They had a problem in the enrichening circuit, some worked well I'm told) and others were awful. I fought a pair for months on a 750 Triumph for months, finally solved the problem, but switched to standard concentrics. My advice is to stay away from the MK2 carbs.

Had a mk11 Amal 34mm on for many years once jetted right never touched it again you can get a single carb front plate for the air cleaner so its looks are not to unchained . Now gone to a pair of premiers wished I had done it sooner.

Forgot to say put a madass linkage kit on. Only one throttle cable once set no tricky carb setting well worth the money

A friend bought a pair of premiers and we tried to install them a few days ago. Found out they would not tickle. The roll pin was too short. My solution was to take a piece of welding rod, turned it down and tapered it, and tapped it down the center of the roll pin and cut it to length. Now the carbs will flood in 3 seconds. But it should have been right in the first place.

JimC said:

Why single carb? To me, putting a single carb on a Commando is like castrating a fine bull.

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Well I´m not going to castrate my bike.....but it seems to me that if you don´t ride hard, but more cruise around at low to medium speed/revs the single carb does the job well enough.

850commando said:

the 34 mik does hava bit of a different sound at idle, but it runs just fine and the the right jetting is posted here.. just search them out what is your elevation above sea level?

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I´m just right down there....at sea level.

batrider said:

You can run either single or dual Mikunis with the air cleaner backplate still on so you don't have to move the ignition key. I tried both of these setups back in the late 70s but the stock twin Amals gave a better combination of power everywhere.

If you do convert and decide to use the cable kit for the choke, remember that the choke lever will operate backwards.

I'd put the money towards fixing up the existing Amals or getting the new Premiers.

Click to expand...

Unfortunatly the bike didn´t have the original Amals when I bought it back after 30+ years, it was equipped with two Mikunis which are from a snowmobile engine I´ve been told. Probably made for 2-strokes. They probably work but I´m going for a single. Maybe I was unclear at the top, my question is if there´s a big difference between a single Mic and a single Mk II Amal.

1up3down said:

right below my post is the March 16, 2018 thread on the single Mikuni V twin Amals actual real world Cycle World magazine road test. In short, the report says the single Mikuni idles like a rock and is stronger, the bike is faster, pulls away from a well sorted out twin Amal setup form 50-80 in top gear. It is only in the quarter mile that the twin Amal set up is 4 tenths of a second quicker. The Mikuni 34 has been fitted to Commando for over 40 years now and is very well known, comes correctly jetted from just about every vender, has an excellent choke for one kick starting, and is Cycle World's preferred choice.

Click to expand...

Again I was probably unclear, I was wondering about any difference between a single Mic and a single Mk II Amal. You don´t hear or read much about the Mk II.

illf8ed said:

The single Mikuni is lower maintenance. Correct jetting May be an issue since the as supplied isn’t quite right. For reference Ken Armani in San Jose has the perfect jet set recommendation for both 750 and 850 Commandos.
Down side to single Mikuni is you cannot use the stock air cleaner and if your 850 is pre MkIII you will need to figure out where to put the ignition switch bracket. I tried a Mikuni on my ‘72 combat for a brief time then returned to the 932 Amals. It had a really strange idle lope that sounded like a Harley idle as well as the other issues above.

Click to expand...

Do you have a link to Ken Armani's recommendations?

So, back to Mik vs MK2 Amal...

MK2 Amals can be made to work very well. There are thousands of late Triumphs our there, twin and single carbs, running perfectly on MK2 Amals.

But... the mistake people make (me included) is thinking they’re just MK1s with a different cold start system. They’re NOT. Read up stuff on t’internet by John Healey. He’s a Triumph man, but gives great insight into the MK2 carb.

The other difficulty is having good data for baseline for settings, especially on a non standard application like yours. It’s bad enough on standard applications...

Read the thread I posted in the Triumph pages on this forum. I just went through a real f*cking headache simply trying to get my new, stock MK2 carbs to work on a rebuilt, stock T140. I got there eventually after doing a lot of research, spending a lot of time on trial and error, and spending a lot more £ on new needles, jets and chrome brass slides. This was despite Amal selling the carbs as being jetted for a T140 in the first place!

The single Mik has the advantage of being sold by trusted Norton suppliers who should therefore provide a good baseline setting. Indeed, hopefully plug n play.

And, having worked with both carbs, IMHO the Mikuni is a better made, higher quality instrument.

So, on balance, if I was fitting a single carb (which I would never do again as it killed performance dead at 5,000rpm. It’s NOT only about performance above 80mph... it seriously reduces how quickly you can accelerate to 80mph, which for me, is a huge part of the fun of a good Cdo) I would fit the Mikuni.

All only IMHO of course.

Just to stray slightly around the topic , i have heard tell of a number of single carb setups which cause excitement on rainy days with the slide hanging up when rolling off the throttle - into corners for instance. Some have even resorted to using the kill switch to slow down for corners.
I have only ever run twin carbs so no direct experience. Perhaps they just don't like being upside down here downunder

ntst8 said:

Just to stray slightly around the topic , i have heard tell of a number of single carb setups which cause excitement on rainy days with the slide hanging up when rolling off the throttle - into corners for instance. Some have even resorted to using the kill switch to slow down for corners.
I have only ever run twin carbs so no direct experience. Perhaps they just don't like being upside down here downunder

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I'm not sure but I think part of the problem here is as you go bigger with a VM say from a 34 to a 36 or 38 the carb will be bigger/taller it forces the cable against the frame backbone and starts it snagging
Either way fitting a concentric spring inside the mikuni one sorts it out

fiatfan said:

Again I was probably unclear, I was wondering about any difference between a single Mic and a single Mk II Amal. You don´t hear or read much about the Mk II.

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No you weren't unclear it's just people misinterpreted your question
I'd have to say the main difference between the VM mic and the mk2 amal is build quality
The mikuni is by far the better carb in terms of build quality and longevity,the body and slide are by far better, the needles and needle jets are better ,the enrichiner jet in the mic dosent seem to have the problems that mk2s sometimes have
But for serious performance you need a TM 40 mic