single vs dual mikunis

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I'm just curious about something. I've noticed everyone seems to prefer the single mikuni setup not the duals. I put a single mikuni on my old bike when the amals wore out and wasn't very happy with it, bike felt strangled on the top end.

It seems to me the dual mikunis would give much better performance so I was wondering why nobody seems to run them. Keeping them in sync can't be that difficult compared to a four cyl bike (I have an old UJM with four carbs. What a nightmare, wish I could put a single carb on that bike!)

As for me and my new Norton, I think I'll stick with the amals. I guess I've become a traditionalist in my old age :)

Debby
 
Single carb

There are some ways around the govener effect of a single carb but like anything it requires a lot of fussing around. As long as your Amals have free idle curcuits and sleeved slides they will serve you well. If you still have your Mic and would like to make it work and have lots of time I could tell you what I have done to mine.
 
One reason not many people run dual Mikunis is their width. They must be splayed to clear the wide float bowl and this creates a problem with trying to fit proper air filters.
I managed to solve that with a couple of K&N tapered units, but they still come well back into the battery box area.
I'm running a pair of 34 mm on a much modified 850 and they breathe pretty well. For my other 850 and my 750, sleeved Amals and new Amals are less hassle.

Ron L
 
Single Mikuni vs Dual

Debby,

You've defined the reason for using dual carbs very well..."doesn't feel right at the top end". Those using single carbs and satisfied are not using the top end much. This goes back to knowing what kind of performance is expected of the engine and using the best setup.

I used a dual 32mm Mikuni setup 15 years ago on a '73 750 Mk5 high compression (RH6 head). The fit was difficult and there are many variables setting up Mikunis including the air filters. Eventually I went back to sleeved original Amals and the stock air box. Look and fit were my choice.

My current '72 roadster has sleeved orginal 932 concentric Amals and with new needles and needle jets runs excellent and returns 55-60mpg economy...also idles fine with the Lucas RITA ignition.
 
Oh hey, that brings up another question. I saw a pair of NOS 932 amals for sale on ebay. Am interested because they have the newer style float bowls with the drain plug, they come with the choke assemby (PO removed that from mine and threw it all away) plus I'd have nice fresh new carbies. But they're 932 not 930 as originally fitted to my 750. Didn't know if they would work on bike...

Debby
 
Debby,
932's will work. However, you will need to use the manifolds from a '74 850. These will blend the port sizes from the 32mm of the carb to the 30 mm of the cylinder head. Alternatively, you will need have the port of the cylinder head opened up to 32mm and use the 32mm X 32mm manifolds from the Combat, any '73 750 or 850 or '75 850.

Jetting and needle settings for a Combat or '73 750 MkIV is a good starting point.

Ron L
 
Sleeved Amals

Debby,

It's my opinion that a sleeved Amal is better than a new Amal. The new body will wear out in less than 10,000 miles where the sleeved instrument will last much longer.

If you want the later parts such as the carb bowls with access to the main jet and the covered tickler pins, these are available and can be added to your original carbs.
 
Guess I'll just keep my original carbs and maybe upgrade a few things and get them resleeved when they need it. I like those new tickler buttons. Maybe they'd keep the gas off my fingers! The price went up too high on those ebay carbs anyway. Thanks for the info guys!

Debby
 
MK 11's

You could always use Amal MK11's. You'll need to change the manifolds.

I use 34MM MK11's and have had great success, with top end, overall performance and idle.

I upgraded the chokes so I have a handle bar control - That works well too.
:lol:

Jerry

single vs dual mikunis
 
Hi Jerry,

I continue to be awed by the quality of your bike!!! :shock:

Do you have any other closeups? I'm using your pics as reference for mine. It's nice to see what it's supposed to look like :)

(Got the goods! Thanks!)
 
dual mikunis

I ran dual 34mm mikunis on my 750 commando. Lots of power, especially up top. Also idled well. You need the splayed manifolds as the carbs are wide, as has been pointed out. I could only get those sock-kind of slip-on filters to fit. I am no longer using these carbs, so if anyone is interested....

I am now using a pair of Amal MkII 34mm, for vintage racing. These have straight manifolds, however I had to do a lot of port matching to get them setup nicely.

I also have a set of 36mm Amal MkII smoothbores if anyone's interested... :wink:

Dave
 
Wow Jerry, those Mark IIs on your bike look really nice! Maybe I'll have to start saving up for a set...

Dana - yes, I've been watching that ebay listing. Lots of good parts I could use. Will just have to wait for the end of the auction to see how high the bidding goes.

Debby
 
Hey JerryDoe, can you email me the model # for the K&N's you are using on this set up of yours? Some one was asking me about them. It seems to be a stumbling block for many trying to use this set up. Thanks in advance. norbsa
 
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