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Fitting Mikuni carbs

john998

Well Known and Active Forum Website User
VOC Member
Hello,
Excellent carbs, I went for the 28mms, these have to be 26mm bored out to 28mm as 28's are no longer made.
Can recommend Motocarb Ltd, good service and knowledgeable.
All you need to do is make up a sleeve that is shrunk on to the original stub,or you can use locktite.
That way you are not damaging any original bit's and return to standard is no prob.
Have Mk2 concentric on the other twin, these are good too but the Mukuni is better, and cheaper.

Regards John.
 

bearbung

Forum Website User
Non-VOC Member
Hi John, thanks, really appreciate that. I've dealt with Allen's who are great also, but I''ll check Motocarb. Brian
 

Vince Farrell

Well Known and Active Forum Website User
VOC Member
I'm thinking of fitting Mikuni carbs to my C Rapide. Any for/against/recommendations? thanks

I have a 28mm Mikuni on my Comet, runs smoothly right through the rev range, starts easily when hot, ticks over great and is easy to tune.

The downside.

1/ The 'choke' adds more petrol rather than restricts the air, as we are used to on old bikes. As it comes from Mikuni, putting the lever down adds far too much petrol for a Vincent. Stu Spalding got round this by putting a piece of wire in the feed hole to cut down the flow; I tried this but the wire wasn't thick enough as it still flooded. I will take it apart again when I get the chance and try something a bit thicker. In the meantime I have taken the old fashioned route, a rubber sink plug with a hole in it rammed into the carb mouth to start from cold, works a charm.

2/ As the carb is fed from the top, it starts to gasp for petrol just before the tank is completely empty. This is not normally a problem, but one day Murphy's Law will make sure I REALLY NEED that last drop to save a push.

3/ Mikuni's look like they should be fitted on a lawn mower.

If you intend to use the bike, fit Mikunis. If it's mainly for show - fit a prettier carb.

Lastly, if you want to use our facilities, get information and pick our collective brain - why not join the club and help fund the system?
 

Robert Watson

Well Known and Active Forum Website User
VOC Member
Plasticbeer -- there is a jet in the bottom of the fuel enrichening circuit. You can get various sizes of them. Fit a smaller one. The Woolly has 34 mm flat slide Mikunis and I had to put very small jets in there. Just starts up on a high idle like a choke normally makes it do. If you are too cheap (I know you Yorkshire types - I was born there) to buy a smaller jet, get a very fine stainless wire (like take a throttle cable apart) and put it in the jet, then solder up the hole, then pull the wire out -- Voila -- a smaller jet.
 

john998

Well Known and Active Forum Website User
VOC Member
Hello, As a fellow Yorkshire-man, and having a careful streak, I have to say that my Mikunis start fine on full enrichment.
Not sure what size jet though. One small problem is the the enrichment appears to be on or off, but it starts better than on the old monobocs. The main differance is that it is more tractable at low engine speed, make it even more fun to ride.

Regards John.
 

Vince Farrell

Well Known and Active Forum Website User
VOC Member
Plasticbeer -- there is a jet in the bottom of the fuel enrichening circuit. You can get various sizes of them. Fit a smaller one. The Woolly has 34 mm flat slide Mikunis and I had to put very small jets in there. Just starts up on a high idle like a choke normally makes it do. If you are too cheap (I know you Yorkshire types - I was born there) to buy a smaller jet, get a very fine stainless wire (like take a throttle cable apart) and put it in the jet, then solder up the hole, then pull the wire out -- Voila -- a smaller jet.

Oh Robert, Robert - if only life was that simple. The 28mm version doesn't have a jet fitted, just a hole drilled in the casting.
If you can tell me where I can buy a smaller hole (very cheap) to replace the one that's too big I'd be pleased, or what about a part exchange deal?
 
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