Mikuni Questions

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Single 34 VM or twin Amal Premiers? Blonds or redheads? Same kind of personal choice question with no real definitive answer. After my original set of Amals finally wore out at 35,000 miles I decided to try the single VM 34 Mikuni kit from CNW. Easy install and it works great. Yes, performance is a bit down on top end, but I don't own and ride a 50 year old motorcycle with modern hi performance expectations. I also was a little disappointed in my fuel mileage as it was a little less than I had hoped for. No big deal. I have since bought a set of Premiers at too good of a price to pass up but they are still in my cupboard waiting for a reason to install them. With the Mikuni I like the fact that I don't need to tickle the carbs and have raw fuel spewing onto my clean engine and garage floor, but I also miss the personal involvement with the Amals that tickling brings into play. Blonds or redheads again.
 
Blonds or redheads!!!!! ????
More like a going to a really good restaurant but only being allowed a starter!
Or a half monty breakfast
 
My comments about single carb/ twin carb were mostly tongue in cheek.
Since Mike has the other Amal carb and manifold in his stash, why not run it and see how it goes?
For my own bike I do tend to shy away from anything which reduces the original performance level of these bikes, a big part of which is the nice pull from 5 k to 6500.
I realize not everyone uses that zone. If you rarely go above 5 k, then you aren't missing much with a single carb mounted.

On the other hand, the twin Amals on my Commando have always worked perfectly from idle to red line. They aren't difficult to tune and once set stay in tune for a long time. When they wear out, a pair of Premieres will go on.
With twin carbs you can have the cake and eat it too.
About the only disadvantage is the cost of one extra carb, which in Mike's case, is a freebie sitting in a box waiting to be bolted on.

Glen
 
worntorn said:
My comments about single carb/ twin carb were mostly tongue in cheek.
Since Mike has the other Amal carb and manifold in his stash, why not run it and see how it goes?
For my own bike I do tend to shy away from anything which reduces the original performance level of these bikes, a big part of which is the nice pull from 5 k to 6500.
I realize not everyone uses that zone. If you rarely go above 5 k, then you aren't missing much with a single carb mounted.

On the other hand, the twin Amals on my Commando have always worked perfectly from idle to red line. They aren't difficult to tune and once set stay in tune for a long time. When they wear out, a pair of Premieres will go on.
With twin carbs you can have the cake and eat it too.
About the only disadvantage is the cost of one extra carb, which in Mike's case, is a freebie sitting in a box waiting to be bolted on.

Glen
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Yep I agree if you dont go over 5000rpm the single carb is much better
The mikuni vm34 is slightly better than a single 32 concentric but there's not a lot in it
 
I think you’ve peaked Baz.

“Sweet but slow” and “having the half monty” were your pinnacle !
 
worntorn said:
And my " Mikuni frontal Lobotomy" never even got honourable mention.

Glen
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Well I liked it!!!
Eddie spoils everything, I was going to mention my infinate amount of monkeys and infinate amount of VM mikunis theory but I won't now
 
The reality is , esksteve got it right ... what the point of thrashing a 50 year old bike ..... we all all been on character full modern bikes that out perform our old bikes with the first 2 or 3 gears .... not in favour of put down humour unless face to face ... seems like way more hero’s online than real life .... what up with that
Craig
 
Taking a Commando above 5k can hardly be called thrashing it Craig!

Of course, as has been said, it all comes down to preferred riding style. Personally, the idea of stifling a Commando at 5k cuts it off smack bang where I want it to be taking off.

I have nothing against those who enjoy staying below 5k, and a Mik will suit them fine.

But I don’t think anyone has any right to criticise those amongst us who simply enjoy riding our Commandos as they were intended.

As to the humour, taking that away from this site would be a very sad mistake !
 
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Craig said:
The reality is , esksteve got it right ... what the point of thrashing a 50 year old bike ..... we all all been on character full modern bikes that out perform our old bikes with the first 2 or 3 gears .... not in favour of put down humour unless face to face ... seems like way more hero’s online than real life .... what up with that
Craig
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I use the above 5 k part quite often just to pass cars/ semis etc quickly. If there was a governor that shut it off at 5 k it wouldn't be a bike I would want to ride.
They handle a bit of 6500 now and then just fine
 
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The argument for single verses twin carb verses amal etc will rumble on forever and I hope it does
Personally I prefer the single TM 40 mikuni
My second choice would be twin 32 mm concentrics
Third would be a single VM 36
Fourth choice a single CV 32 mikuni
And in joint fith place would be a single 32 concentric or a 34 VM mikuni
These are all the carb set ups that I have personally tried
I regularly ride above 6000rpm but rarely go above 7000 I'd really hate to blow this one up !! But having said that I'd make dam sure I built it better next time,
Each to their own in these matters
I'm sorry if my crap sense of humour offended anyone
I welcome criticism of my bike or my treatment of it,or its long list of modifications
Above all I enjoy my Norton and hope others to enjoy there's
 
To imply that a single carb totally runs out of steam at 5000 rpm is false. True, it doesn't quite pull like a twin carb, but the limitation comes from the manifold not the carb size. Only one cylinder is on the intake stroke at a time so in actuality a 34mm is going to pass more air than a 32mm. It's that wicked little bend that the manifold makes that that screws things up at higher RPMs. I too prefer the all out performance of the twin Amals but I also like the simplicity of the single carb set up. Triumph said that there was a 3hp difference between the Tiger and the Bonneville so my guess is that with the Norton it would be about the same. If I really wanted to wring out the most performance from my Norton I'd loose 40lbs but that's no fun. Hey, that just brought to mind Baz' great statement statement about the half monty breakfast.
 
Jim Comstock posted some dyno numbers on the single Mikuni 34, if memory serves it was 36 or 38 max on his dyno.
That sounds like about ten horses missing.
I'll see if I can find the number.

Glen
 
Looks like the 850 with single Mikuni 34 made 40 at rear wheel on that day.
The other bikes on that graph are bored out to 880, both making a lot more bhp, but not a good comparison.
As a guesstimate, a good standard 850 might be around 46-47 on that dyno on that day.

Glen
 
So if I understand correctly, riding with a single 32 Amal MKI is like a half Monty but dual Amals gives me a Full Monty Commando that I can ride "commando" style for even more fun?
 
I am also of the mind that it is the ‘unkind’ manifold that’s the bottle neck on a Cdo. On a Triumph it is less of an issue. So the lost BHP will be more on a Cdo.

Of course the power does not ‘stop’ at 5k. But it certainly stops increasing, making any further revs just pointless.

It will be a bigger issue for anyone wanting to ‘hop up’ their Cdo with cams or porting etc as, basically, it won’t yield the potential results and the ‘bottleneck’ remains unchanged.

I had a 36mm Mik on a stock 850 and it definitely ran out of steam at around 5k.

It was nice below 5k, but I have also ridden a friends stock Cdo, and that was just as nice, complete with its new Amals.
 
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