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High fuel consumption on a single Mikuni?

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I am using a 1971 750 Commando with a single VMMikuni carb. Bike starts and runs great with no smoke or misfire, but the petrol consumption is 30mpg and the plugs are sooty. I am assuming I should drop the needle one notch for starters? Thanks Rob

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Sounds like you are running with the choke on Robert.

My 1976 Mk 3 Commando runs on a single 32mm Mk 1 Amal and since the conversion 5 years ago, fuel consumption has gone up from 45 mpg average to 68 mpg average. The Champion spark plugs are a nice light brown too.

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Previously robert_james1 wrote:

I am using a 1971 750 Commando with a single VMMikuni carb. Bike starts and runs great with no smoke or misfire, but the petrol consumption is 30mpg and the plugs are sooty. I am assuming I should drop the needle one notch for starters? Thanks Rob

Perhaps an obvious point, but is your air filter ok?

Mark 72 commando with vm carb.

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Previously robert_james1 wrote:

I am using a 1971 750 Commando with a single VMMikuni carb. Bike starts and runs great with no smoke or misfire, but the petrol consumption is 30mpg and the plugs are sooty. I am assuming I should drop the needle one notch for starters? Thanks Rob

well it sound like you need a US carb kit from Burlen LTD carburettors then you get 80 mpg, as they claim , yours anna j

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Previously anna jeannette Dixon wrote:

Previously robert_james1 wrote:

I am using a 1971 750 Commando with a single VMMikuni carb. Bike starts and runs great with no smoke or misfire, but the petrol consumption is 30mpg and the plugs are sooty. I am assuming I should drop the needle one notch for starters? Thanks Rob

well it sound like you need a US carb kit from Burlen LTD carburettors then you get 80 mpg, as they claim , yours anna j

Rubbish, the Mikuni will work superb when properly set up. I get 50-60mpg with the standard twin Amals ridden normally and over 60mpg when ridden steady on my 850 Commando.

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Previously robert_james1 wrote:

I am using a 1971 750 Commando with a single VMMikuni carb. Bike starts and runs great with no smoke or misfire, but the petrol consumption is 30mpg and the plugs are sooty. I am assuming I should drop the needle one notch for starters? Thanks Rob

Robert i'm using a vm 36 mikuni on my 850,I was put wise to the carb jetting by Micheal Sullivan he pointed me to the Ohio Cafe Racers web site

failing that give Motocarb a phone call, uk based and extremely helpful

Steve Elston

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Why anyone would want to put a Japanese carb on a British bike is beyond me? Still, it's your bike. But while you can buy a new Amal or dare I say SU, if you are into shoe horning, there must be more street cred and pride in supporting something closer to home, especially when they work so well.

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In 39 years of Commando ownership I have tried just about every combination of carb on mine. The SU was good but too difficult to start, single Mk1 Amal runs out of puff above 75MPH, Single Mk2 Amal good but freezes up at high throttle settings, Single Mikuni by far the best for general running and performance. Twin Amal Mk1 ok for top end but annoying hesitation coming off the pilot jet and crappy pilot jet design. Currently running a pair of JS Motorsport PWK flatslides, probably made in Taiwan. Best yet. Do I care that they are not British? nope. not as such.

Robert, sounds like your jetting is completely wrong for a Commando. If you can give me a day or so I'll come back with the correct jets sizes for a 34mm VM Mikuni if that is what you have.

Neil, bet your innertubes are made in India and your battery in China.

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Previously david_evans wrote:

In 39 years of Commando ownership I have tried just about every combination of carb on mine. The SU was good but too difficult to start, single Mk1 Amal runs out of puff above 75MPH, Single Mk2 Amal good but freezes up at high throttle settings, Single Mikuni by far the best for general running and performance. Twin Amal Mk1 ok for top end but annoying hesitation coming off the pilot jet and crappy pilot jet design. Currently running a pair of JS Motorsport PWK flatslides, probably made in Taiwan. Best yet. Do I care that they are not British? nope. not as such.

Robert, sounds like your jetting is completely wrong for a Commando. If you can give me a day or so I'll come back with the correct jets sizes for a 34mm VM Mikuni if that is what you have.

Neil, bet your innertubes are made in India and your battery in China.

Hi David, You are right about the Inner tubes and the battery's but if there were a UK made alternative I'd take it, that's the point.

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It's interesting that Commando owners using Mikunis seem to fall into two distinct groups. The first just fits and forgets, the second spends its life buying an ever increasing number of jets/slides/whatever and never gets it exactly right.

I have no idea why this is and equally no idea what's inside my Mikuni as I have never needed to look, falling into the first group as I do.

I agree with Dave on the main point that it's the best option I have found for the Commando although I have never looked at the fancy Gardner or Keihin options.

The ultimate of course is the fuel injection route; it transforms the bike but also transforms the bank balance in the process.

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Hi Peter, I'm here and today and still ridingthe flag!

I think the Italian Job frames were made around 1972 andstoppedbecause they had to be rectified before assembly in a jig called 'The Donkeys Dick.' The dick part had to go through the head stockandin so many, did not. My Commando is a1976 Mk3..

However, before you remind me, I'll have to replace the originalFrench instruments for a pair of Smith's.

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Previously neil_wyatt wrote:

I think the Italian Job frames were made around 1972 andstoppedbecause they had to be rectified before assembly in a jig called 'The Donkeys Dick.' The dick part had to go through the head stockandin so many, did not. My Commando is a1976 Mk3..

My Mk3 frame was out every which way. Upon getting every thing parallel rear wheel c/l was approx. 1/4" away from frame center line. So much for British craftsmanship.

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To try & answer Robâs original question, first off you need to work out where, or at what throttle position, the engine is running rich. The needle will only affect the mixture in the mid range, roughly ? to ? throttle. If the richness is all through the throttle range, I would suggest first trying a smaller main jet as this affects the mixture through the entire throttle range & is the first thing you need to get right, as changes here will affect everything else. In the absence of a rolling road, find a nice quiet stretch of road or go for a track day, hold the bike at full throttle for a few seconds then pull the clutch & kill the engine. Do this where there is somewhere safe to stop, then remove the plugs & see what theyâre like. (If youâre on a track, kill the motor at the pit entrance & you can usually coast into the pit) If theyâre very black, then you know the main jet is too large & itâs time to start experimenting with smaller jets. If, on the other hand they are ok, go through the same procedure but hold the bike at ? throttle instead of full & see what results you get, then try at ? & 1/4 throttle. You should then have a reasonable idea as to what your mixture is throughout the rev range & from there you should be able to narrow down where your problem is. Pilot jets & throttle cut away only affect the lower end of the range, up to about ? throttle, the pilot controlling the lower half & the cut away controlling the upper half of that range. The other thing to check is that the choke, or enrichment device, is shutting off properly, it wouldnât be the first time I had found this to not be sealing correctly when closed, thus meaning you would be running with choke on all the time.

Properly set up the Mikuni is a good carb, far better than anything Amal has to offer, & with the possible exception of an SU is indeed probably the best readily available & reasonably priced option for a Commando. For a 750 I would recommend a VM34 unless you are after maximum top end. The 34 will give you better bottom end, mid range & economy at the slight expense of top end BHP.

Hope this will be of some help to you,

Regards, Tim

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Hello there,

I would very much second the suggestions mentioned by Tim but in addition I would strongly recommend that you should remove the carb and check that the float needle valve is seating correctly and also check the float height. Dirt in the needle valve or too high a float level are common reasons for rich running and poor mpg with Mikunis or Keihins. The carb is simply flooding and giving too rich a mixture.

This is assuming that the carb is correctly st up in the first place and there is no other obvious reason.

Patrick

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Patrick, thanks for adding that, I should, of course, have included your suggestions in my reply, this should be checked first!

My only excuse for my omission is that my tea was rapidly approaching the table & my mind was drifting in that direction.blush

Regards, Tim

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Hi, thanks for posts. I dropped the needle one notch (i.e. in position 2nd from bottom of 5 notches) and noticed that the rubber manifold has cracks. Rearward of the carb it has a round K&N filter fitted. Now it won't start.

I don't want to spend much more time or money on this loan bike and may just use my 1956 Matchless till I get my own Commando being built from spares. I will spend a few more hours fiddling though, so posts are informative and much appreciated. The old boy who will be setting up my bike after building the engine is a bit of a purist, and wants dual Amals, so I will go with that.

In case of interest I am in Invercargill NZ, but grew up in rural UKwith Commandos everywhere, and decided I wanty a shiny Jap bike instead. I recently had a Buell Ullyses for 2 years but the Commando has better torque, character and balance, plus a rear brake that actually works. Funny how life goes full circle...

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As a digression [ off topic! ], Robert just makes it to being the NOC's most southerly Member as we have another Noccer living a couple of miles North of Invercargill. For those who have not been there, it's about the last thing that happens before you fall off the bottom of South Island.

Webmaster

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The correct jetting for the VM34 Mikuni for a 750 is as follows

Main Jet 220,

Needle Jet 159 PO

Needle 6DH3 (clip in middle groove)

Idle jet 35

Slide 3

Idle air jet 2

You can download a good manual for tuning Mikuni VM carbs free and it explains the finer points of the pilot air circuit (Just google it) The slide and Needle jet are quite expensive compared with an Amal but they are much more complex components and the slide, as I'm sure you are aware, is chrome plated brass. Yes it is Japanese but if you prefer riding to fettling, (or dare I say it, looking at it) it's the way ahead. With the above jets it's fit and forget.

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Thanks for informative posts. Carb is a 34 with a 240 main jet. Floats fell out of the bowl on disassembly as there are no retainers on the pins. Is this standard? Needle back in mid position. Bike still won't start despite good spark at plug. Limited mechanic skills waning...

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I have been using the original twin Amals, and set up as per the manual I'm getting over 50mpg. From what I have seen about the Burlen carbs, I would go down this route before fitting a Mikuni or SU etc.

The result of the combustion process doesn't lie - you just need to understand it to be able to rectify it, with a four stroke it's easy, with a two stroke the result could direct you in the wrong direction as many will have experienced as the petrol / oil ratio also plays a big part.

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Rob, the float arm hinge pin should be a push in fit in the carb body, not really tight, but tight enough not to fall out, there is nothing else to retain it. The floats slide up & down on guide pins in the float bowl & engage with the arm, pushing it up to close the needle valve. There is nothing but gravity to stop them jumping out when you remove the float bowl. If the bowl is full of petrol, they will float up & can fall out.

Here is a link to a tuning guide, which also shows an exploded view of the carb, it may help. http://www.mikuni.com/pdf/vmmanual.pdf

If the bike was starting & running ok, just a bit rich, & now wont start, it would suggest something has changed, go back & re-check anything you have touched, itâs not difficult to reassemble the float bowl with a float jamming the float arm & holding the needle jet closed, therefore no petrol, no start.

Ashley, could you explain what you mean by âFrom what I have seen about the Burlen carbs, I would go down this route before fitting a Mikuni or SU etc.â Burlen supply Amal, SU & Zenith, but are nothing to do with Mikuni?

Regards, Tim

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From other forums it seems that that the Amals they supply with many improvements in materials and tolerance have had a good reception. I fully understand that in past the quality of Amals has been very hit or miss with lot of owners loosing confidence with them, and the alternative was Mikuni, Flat slide, SU, single Amal etc. For the price of two new Burlen Amals, I would imagine the cost of other carbs is more. In my opinion I reckon it now makes sense to replace like for like.

I also meet many who have returned back to Amals having had problems in the past with other carbs that have been unable to resolve.

I also can not remeber the last time I was out and about and met another Commando fitted with a carb other than Amal.

And No, I do not work for Burlen Fuel Sytems!

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Ashley, if you haven't seen another Commando with anything other than Amals then you probably don't go very far. The single mikuni conversion is very popular at NOC events. Amals have improved their pilot circuit and the new slide is better but the body is still made out of a poor zinc aluminium alloy.

Robert has Mikuni on his borrowed bike and is I suppose, just trying to get it to run better. I doubt he is going to shell out for a new pair of carbs for the owner but he may improve his ride with a few new jets and a little time

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Previously john_mcnicoll wrote:

Previously anna jeannette Dixon wrote:

Previously robert_james1 wrote:

I am using a 1971 750 Commando with a single VMMikuni carb. Bike starts and runs great with no smoke or misfire, but the petrol consumption is 30mpg and the plugs are sooty. I am assuming I should drop the needle one notch for starters? Thanks Rob

well it sound like you need a US carb kit from Burlen LTD carburettors then you get 80 mpg, as they claim , yours anna j

Rubbish, the Mikuni will work superb when properly set up. I get 50-60mpg with the standard twin Amals ridden normally and over 60mpg when ridden steady on my 850 Commando.

yes but a US Carburettor set up right gives you a good top end of 110mph and at 70mph a mpg of around 80 mpg fact , my friend set up on his 900cc custom Honda with a single US carburettor does just this, so you need too say rubbish too this, and why are we all running on petrol in the first place when we can happily run on HHo clean and green technology and cost very little at all the technology is out there for all to explore . if you put your brain in gear . But by putting you brain in gear is then off topic and the web-master will merrily jump all over you, so there are on winners on this web page yours anna j

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I have to agree with Ashley on this one. I am in fact a fan of the single Amal on twins. It is true that the Mk 1 bodies are made of poor material, insisted by our bike industry to cut the cost. And I don't think we have considered the single Mk2 Amal carb on this thread yet?

Today there are low wearing slides available, stay up floats and Martin Bratby can reline your carb body when wornso job sorted and street cred maintained.

I don't do a lot of milage on my Commando, but once I was told many years agothat a260 main jet was where it needed to be, it has never ran better since. This has been for the last 2,000 miles coming up and no fettling required since.

Maybe we should start pushing Amal carbs for olderJap bikes and see how they like it? Robert's loaned Command doesn't likethe Jap carb and thank goodness that Amal appears to be in the majority, that must say something?

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Previously anna jeannette Dixon wrote:

Previously john_mcnicoll wrote:

Previously anna jeannette Dixon wrote:

Previously robert_james1 wrote:

I am using a 1971 750 Commando with a single VMMikuni carb. Bike starts and runs great with no smoke or misfire, but the petrol consumption is 30mpg and the plugs are sooty. I am assuming I should drop the needle one notch for starters? Thanks Rob

well it sound like you need a US carb kit from Burlen LTD carburettors then you get 80 mpg, as they claim , yours anna j

Rubbish, the Mikuni will work superb when properly set up. I get 50-60mpg with the standard twin Amals ridden normally and over 60mpg when ridden steady on my 850 Commando.

yes but a US Carburettor set up right gives you a good top end of 110mph and at 70mph a mpg of around 80 mpg fact , my friend set up on his 900cc custom Honda with a single US carburettor does just this, so you need too say rubbish too this, and why are we all running on petrol in the first place when we can happily run on HHo clean and green technology and cost very little at all the technology is out there for all to explore . if you put your brain in gear . But by putting you brain in gear is then off topic and the web-master will merrily jump all over you, so there are on winners on this web page yours anna j

As usual this is no help and does not answer the original question. Not surprising that you have problems with the web-master !

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Ashley, David has pretty much said it all in his reply, Amal bodies are still made of poor quality metal & there are probably as many Commandoâs running around on alternative carbs as there are on Amals. As for price, two new concentrics are going to cost you £264 or thereabouts, (£131.99 each) Iâve recently fitted a Mikuni VM36 conversion to a customers MK3 Commando, (his choice & request) & it came in at a shade under £240 for the complete kit. A single 36mm MK2 Amal conversion kit would have been a similar price although I notice Norvil no longer sell MK2 Amals as they reckon MK1âs are better (not that their opinion carries much weight with me).

Neil states 2000 miles without fettling, which is ok, but I know of at least two commandoâs with Mikuniâs that have done in excess of 20,000 with nothing more than occasional air & fuel filter maintenance & my own SU supplied Commando has done over 30,000 miles with nothing more than the occasional squirt of oil in the dashpot & air filter maintenance, there are not many Amal concentrics that manage that mileage without replacement slides & rebored or sleeved bodies. & let's not forget that had Norton survived a little longer, they were about to ditch the Amals, Commando's would have been fitted with the SU as standard.

None of this is relevant, however, as the original question from Rob was what should he do to address poor fuel consumption & rich running on his borrowed machine. Nowhere has he asked for recommendations as to what carb he should fit, but he has been bombarded with suggestions & opinions telling him he needs to spend a small fortune changing the carb to someone elseâs preference.

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Thanks Tim, as I said if Rob checks his jetting and other settings he might just need to play with the settings if the carb is correct. From my experience with Mikunis you will find it impossible to start if the slide is right at the bottom of the body, bring it up on the throttle stop until you can just see daylight under it and go from there. In addition ensure that the enrichment circuit is closed off properly once started. That is the plunger that acts as a choke should be fully down. ( the lever that operates it should be up unless it is fitted with a handlebar control) The plunger has a rubber face to seal off the fuel flow when not required. This could be missing.

If I hadn't gone to twin flatslides out of a sense of curiosity, (and surplus cash) I would still be running a single VM34.

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Now Tim, I think it a bit unfair to compare my almost 2,000 miles since conversion to single Amal in 2004 with no issues once I got the jetting right, with other examples that have done higher mileage. I would expect this to last more than 20,000 miles though I know from experience that by 30,000 miles the Amal'(s) will be well worn and either replaced or refurbished.

As for replacement cost, RGM sell a newR/H Amal Mk1, set upto your requirement for £109.00 + VAT = 130.80. You could buy a Wassell for £30 less but Ican't comment on that.The 2-1 Mk 1 Manifold is £54.90+ VAT.

I couldn't find anything Mi*uni on the RGM site! If you have a Pre black box air filter then all you need is a front plate: £21 + VAT or £34 in stainless + VAT. You can make up the fuel line and throttle cable yourself.

As for answering the question, my first observation was to check if the choke was left on in part or full. What it sounded like. That is as far as I could go with not having one of these Oriental, unnecessary contraptions. So, like others, my next advice to solve the problem was to use the single Mk 1 Amal as I know this conversion works, unlike Robert's Mi*uni in its current state! I thought offering a solution was the end game?

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Previously david_evans wrote:

Ashley, if you haven't seen another Commando with anything other than Amals then you probably don't go very far. The single mikuni conversion is very popular at NOC events. Amals have improved their pilot circuit and the new slide is better but the body is still made out of a poor zinc aluminium alloy.

Robert has Mikuni on his borrowed bike and is I suppose, just trying to get it to run better. I doubt he is going to shell out for a new pair of carbs for the owner but he may improve his ride with a few new jets and a little time

Although I have no personal experience of the Premier Amals yet, I have not heard one single bad report. The slides now have a hard anodized coating and I would imagine provide a low coefficient of friction between the slide and body. Where do you get your information that the new bodies are "poor zinc aluminium alloy"?

Your comment; "Twin Amal Mk1 ok for top end but annoying hesitation coming off the pilot jet and crappy pilot jet design." is based on your personal experience I assume. With the carbs set up properly my old pair of Amals display none of these symptoms.

I take it you've now sorted the lack of top end power due to fuel flow on your Keihins?

Ahsley's advice on a new pair of Amals is sound in my opinion.They would provide an instant fix with good performance and save Robert the time and expense of attempting to fix the Mikuni. If the Mikuni was so good, as you claim, how come you haven't got one?

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Previously neil_wyatt wrote:

Now Tim, I think it a bit unfair to compare my almost 2,000 miles since conversion to single Amal in 2004 with no issues once I got the jetting right, with other examples that have done higher mileage. I would expect this to last more than 20,000 miles though I know from experience that by 30,000 miles the Amal'(s) will be well worn and either replaced or refurbished.

As for replacement cost, RGM sell a newR/H Amal Mk1, set upto your requirement for £109.00 + VAT = 130.80. You could buy a Wassell for £30 less but Ican't comment on that.The 2-1 Mk 1 Manifold is £54.90+ VAT.

I couldn't find anything Mi*uni on the RGM site! If you have a Pre black box air filter then all you need is a front plate: £21 + VAT or £34 in stainless + VAT. You can make up the fuel line and throttle cable yourself.

As for answering the question, my first observation was to check if the choke was left on in part or full. What it sounded like. That is as far as I could go with not having one of these Oriental, unnecessary contraptions. So, like others, my next advice to solve the problem was to use the single Mk 1 Amal as I know this conversion works, unlike Robert's Mi*uni in its current state! I thought offering a solution was the end game?

Neil

Is your keyboard made by Amal?, its displaying the letter k as an *

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Neil, the point I was trying to make is that 2000 miles is not really enough to make an accurate judgement, it will be interesting to hear your views when you have done 20,000 miles on your Amal, I genuinely hope youâre as happy then as you are now. You also state that you have had no issues ONCE YOU GOT THE JETTING RIGHT, this is the most important point here, what ever carb you fit, it must be jetted & set up correctly for the particular engine it is bolted to! Two engines that on the surface appear identical, can have quite a variation in their carburation requirements, a carb that runs perfectly on one engine may not perform well at all if transposed to another, it will need tuning & setting up to itâs particular application. It seems perfectly acceptable to have to re-jet & set up Amals to work properly, yet itâs expected that alternatives should work straight out of the box?

With regard to replacement cost, I was answering Ashleyâs statement that âFor the price of two new Burlen Amals, I would imagine the cost of other carbs is more.â

I will confess my experience with Amal premierâs is not huge, I have helped out with a couple in so far as jetting & basic setting up, the pilot system is a vast improvement, in that you can gain access to clean & the float is an improvement over the original, with a bendable tab for adjusting float levels, but I have had to helicoil the threads for the float bowl screws on one after the owner tried to tighten them a little to stop a fuel weep, he was able to strip them quite easily, suggesting the material is quite soft.

My experience of Mikuniâs goes back to 1987 when I had a 750 Commando. An American friend said they had been fitting them to Commandoâs for some time & offered to get a kit sent over for me to try, at the time it cost me next to nothing so was a no brainer. Once fitted & set up (it came with a selection of jets & two different slides) it transformed the bike, much better grunt & more mpg. I done a good few thousand miles on it before I moved the bike on with no issues.

It may sound like Iâm anti Amal, which is not true, all of my british bikes except my Commandoâs are fitted with Amals, although theyâre all Monoblockâs apart from the unmentionable from meriden which has itâs original Concentric still in place. Having said that, itâs probably done less than 2000 miles since 2002, after all, whoâs going to take a T****** out when you have a Norton or two to choose from? The fact is, whilst it was quite happy on them when they were new, my Commando wore out two sets of Concentrics in under 10,000 miles (admittedly the first set werenât new when I got the bike, but were in good condition) & I struggled to get more than 40mpg, & when you have a Roadster tank, that doesnât give you much range. I fitted the SU, instantly doubled my mpg &, as previously stated, in over 30,000 miles have not had to touch it. I accept there are a lot of folk out there happy with their Amals, but for me, at least on the Commando, thereâs no competition.

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Fair enough Tim, and you are right when you say that no two engines are the same. However, from the experience of Commando carb setting, luck or not, when setting up the 30mm Mk 1 single Amal on my 650SS it was perfect all the way through from the outset. Shame the motor has to be taken down.

For the 850 Commando, RGM suggest 270 /260 main jet. Mine came with the 270. I spoke to the Club's Commando expert who has the same set up as me and he said his bike runs perfectly (Say no more) and uses a 260 main jet. After that it was magic! There was actually a slight flat spot at just below 3K rpm. (I have used Mk3 Boyer since 1989) A new battery, would you believe it cured that.

At the end of the day I believe both carbs can be set up to work well, so what are the issues?

1) I'll bet Amal parts are cheaper and more easily obtainable.

2) I remember back in 1974/5 the adverts telling us to Bike British and ride the flag! Union Flag or rising Sun?

3) Who's economy would you rather support? UK or Japan?

My car BTW is a UK made MG and the KKKKKKKK works fine on this keyboard.

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Believe it or not, Neil, Iâm 100% with you on supporting British industry whenever I can, but for many years Amals were made in Spain, Iâm not even sure theyâre UK made now. That left me with the choice of supporting the Japanese economy, as you put it, or the Spanish economy. Some choice, so I went with the SUsmiley That left me with a clear conscience over patriotism, & I felt I had only carried out an upgrade/modification that Norton had developed with SU & which Norton themselves were due to introduce on the Commando in 1976. To me a win win situation.

As for my car, well, I have a 1967 Hailwood, Liverpool built Ford Corsair, which takes up daily service & a Hethel, Norfolk built Lotus +2 For a bit of fun. The modern car which the missus useâs is a Ford Mondeo, unfortunately probably built in Europe somewhere.

It saddens me no end that if you want to buy a UK built family car now, you have to buy a bl**dy foreign thing. Where did it all go wrong??

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Simon, the director of Amal was interviewed in a classic mag recently and admitted that there had been no change the the material that the bodies are made of. Your Mk1 concentrics work well Simon because you had them re-sleeved and machined to a very close tolerance. My "Keihins" are actually PWK and worse than that they are made not in Japan but Taiwan. They are working fine. If you go back to half way down the first page of this thread you will see that Rob is not in the market for a new pair of carbs because the bike is not his.

Digressing slightly, one of the Shropshire branch members and the guy in Telford that I assisted recently both had new carbs supplied by Norvil. (whether they are genuine Amal is another question) both these members have experienced problems with their new carbs and have converted to Mikunis with no further issues. These Amal carbs were both pre premier versions.

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I did like your last response Tim and found itmost encouraging. I know that Amal production did go to Spain but they were not properly finished and so assembly and finishing came backto the UK. I checked out 'Access Norton', there was a thread: Amal v Wassall (2012) and a gentleman I have dealt with at Amal explained that quality control was not good enough and so the bodies were finished in Salisbury and assembled there and as at 2012, only between 2 and 4% of bodies are sourced overseas to meet demand. (Demand suggests we are not all going Japanese...I really think so !!!)

David, I wonder if the carbs bought from Norvil were Spanish made old stock? Shouldn't be difficult to find out if the boxes are still about. Did Mr Emery do anything about it? If you want Taiwanese carbs on your Norton when there are British options (SU/Amal) then that is a matter for you but not something I would like to see. My opinion only.

We have come a long way from trying to get Robert's loaned Commando running. I hope one way or another it does run with whatever carb. I just wish there was as much enthusiasm for providing 57/58 pre Featherbed engine plates for singles.

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If there has been no change in the material the carb bodies are made from, they should last a good while. I am running a 276 which has done a genuine 45,000 miles. The only replacement part has been a float clip. Interesting to know if the concentric bodies are the same alloy. If they are not, why not?

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Gordon, I mentioned this earlier in the thread. The Mk 1 Concentrics sent to the bike industry for evaluation were found satisfactory and cheaper than the monoblock BUT the British bike industry wanted them cheaper still, hence the cheaper fast wearing material, the only place cost reduction could be made. When you get slides and bodies made from the same poormaterial you are going to have fast wear. My original Commando 932 Amals were past their best before 29,000 miles and that was with the black box air filter fitted. Running without an air filter, like bore wear can only decrease carb life. So, it was no surprise to hear of tales of faster wear rate. I believe at one stage Norton tried to lubricate the slides on the Commando to reduce wear.

Now all that said, when your carb body is worn you can simply have it relined/ sleevedwith durable material for around half the cost of a new Mk 1 and the job is sorted. (Returned better than a new one) My Commando carbs for a single (+my 16H pre monoblock) are the only carbs replaced, all others fitted new from the startand it will be interesting to see how they last, especially as only the Commando uses an air filter at the moment. Apart from the 16H, all my carbs are Mk 1 Concentric, such is my faith. However, I will be using a monoblock on the 1960 99 under construction but that is just for originality. (£149 + VAT from RGM to your spec)

Has Robert got that Commando running yet? That is what this is all about and perhaps Amal is the answer after all? Prove me wrong!

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Previously david_evans wrote:

Simon, the director of Amal was interviewed in a classic mag recently and admitted that there had been no change the the material that the bodies are made of. Your Mk1 concentrics work well Simon because you had them re-sleeved and machined to a very close tolerance.

David,

your missing the important point regarding coefficient of friction between materials. It dosen't matter if the body material is the same alloy as before as long as the slide has a suitable surface finish to provide the low C of F. I doubt if the Amal spokesperson would have stated the material was "poor".

Digressing slightly, one of the Shropshire branch members and the guy in Telford that I assisted recently both had new carbs supplied by Norvil. (whether they are genuine Amal is another question) both these members have experienced problems with their new carbs and have converted to Mikunis with no further issues.

Not true, as I know one of these people had/has problems regarding a rich mixture.

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Neil my friend, I must confess to being super impressed with your steadfastness, patriotism & brand loyalty, if only there were more like you we may still have a manufacturing industry. You should be an inspiration to us all.

And I do mean that quite sincerely

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Thank you Tim, I stopped using my local fruit and veg shop last week, I kept telling them that UK Conference pears were available, just over the road at Sainsbury's but they insistedstaying Dutch. I insisted going to Sainsbury's and also collecting Nectar points. However, I'm all for supporting small business as long as they are supporting the UK.

Just look at the profits from Jaguar Land Rover going to India, instead of helping to pay off our crippling National debt.

I stay out of the 961 threads but I have heard it first hand in the fleshthe problems with high oil consumption. I'd like to see a new range of new Norton's but if you can't do a 50 mile run to Scarborough without topping up with oil then then the future is not good. I hope it's sorted out as a priority before we lose whole bikes, never mind just the carbs and plugs to the Japs!

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Whatever I say Simon, you will probably take the contrary view. You are quite good at that. Pop in to the next branch meeting and catch up with the latest hot poop

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Interesting debate. I will be going withtwin Amals but I can see that the Mikuni has higher quality machining/materials, and therefore more durable with less maintenance.

I just had a look at the bike and it has good sparks, petrol is getting to the float bowl without overflowing, and the 'choke' lever seems to be operating the plunger appropriately. The cable pull from the twistgrip is good with no slack, and raises the slide cleanly.

No go, or even the hint of a misfire. Baffling situations like this is why I farm the bike out to high skill/low cost mechanics when I can find one. Unfortunately these paragons are always busy with other low skill owners, so I will wait till the weekend to have another look. Thanks for all the posts.

 

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