Mikuni Round Slide vs. Flat Slide carbs

[Koncretekid]

I have to buy a carburetor for my BSA B50 for the new build.  For the last two years I used a 40mm Amal mark II, which is similar in construction to the Mikuni Round Slide carbs, with 36mm port size.  My new cylinder head will have a larger intake valve (1-7/8" vs.1-25/32") and larger port size (40mm).  My engine builder recommends the 44mm Mikuni round slide.  I was thinking that a 42mm flat slide might be a better choice to  make sure the fuel(gas) stays in suspension with the relatively small port size.

Can anybody shed some more light on this choice?

Tom

[ol38y]

IMO, the flat side is a better carb, with an accelerater pump and parts are more readily available. A number of years ago I was looking for some 38 round slides and found good prices at Sudco. The 42 flat slide is used on Sportster conversions so they can be had on ebay sometimes cheap. FWIW

[Koncretekid]

IMO, the flat side is a better carb, with an accelerater pump and parts are more readily available. A number of years ago I was looking for some 38 round slides and found good prices at Sudco. The 42 flat slide is used on Sportster conversions so they can be had on ebay sometimes cheap. FWIW

Thanks for the recommendation.  I bit the bullet and ordered a new HSR42, mainly because I have never bought a carburetor off eBay that I didn't have to completely rebuild.  I believe the 42mm will be better at keeping the fuel atomized than a 44mm round slide, especially since I can't get the intake port opened up beyond 38mm. Intake and exhaust will have to wait until June since I'm in Colorado until then.

Tom

[beerbellykelly]

the HSR is a superb carb-many adjustable circuits,well made and some good upgrades available-only down side is- there so big.
great on the turbo bikes too.

[you can tell im an aircooled electronics free type a rider]

good luck and see you on salt next year.

p.j.

[Koncretekid]

the HSR is a superb carb-many adjustable circuits,well made and some good upgrades available-only down side is- there so big.
great on the turbo bikes too.

[you can tell im an aircooled electronics free type a rider]

good luck and see you on salt next year.

p.j.

Thanks beerbelly,
Glad to hear that they work good on Turbo bikes too.  But I don't know if the BSA will like a Turbo.  Interesting food for thought.
Tom