Mikuni VM 33 Carbs

Please explain the choke function of a VM33, compared with the BS34?

It's an enriching circuit not a choke. A choke is a flap that "chokes" the carbs thus forcing more fuel than air.
Steve

Got my new vacume port adapters (AKA nipples) yesterday. They're for Yamaha fours. Two long and two short. They will work for the two inside being they are long enough to get to easily. I need to get two set screws to plug the holes the PO munged in, drill and tap new ones at the 5:00 and 7:00 position respectively. Carbs will have to come off again and will JB weld them in When I'm ready, could have made my own but $10 delivered I can do other things like my new cush drive rubbers I just got. That will be done today. I've been wanting these things for years. One thing at a time. :whistle:
Steve


Motion pro :ohmy:

swest wrote: One thing at a time. :whistle:

Will you install them to be accessible by reaching underneath the carbs? I was thinking about that, where the best location would be, and also that you could tap the holes and thread them in with a coat of sealant on the threads, skipping the nuts and o-rings.

If you didn't have a provision to vacuum synch the VM33's, how would you be able to get them adjusted properly?

The holes are already drilled and tapped. at 5:00 and 7:00 on the inside two. I'll unscrew them and JB Weld the new "nipples" in their places. The nut will act as a stop so I don't go in too far. The outside ones I will have to drill and tap myself at the same positions. I'll glue set screws into the old holes. They say setting them on the bench is good enough. HORSE PUCKEY. I put them on my carb styx and stumbling goes away at low idle. Raised my needles one notch so I have to do it again if I'm satisfied in how it runs.
Steve

Reference BS34, VM33-A14 Mikuni carburetors. When tediously tuned to attain the best possible operation, which carburetor will render the best performance, overall and otherwise? Please elaborate...

That I don't know. Are the BS carbs CV style? Here's a clip on the 33's. My slides don't have the cut outs.
Steve

swest wrote: That I don't know. Are the BS carbs CV style? Here's a clip on the 33's. My slides don't have the cut outs.
Steve

Thanks Steve, nice clip. The BS34 are the CV style. Vacuum lifts the slides/needles, and the throttle control cable mechanically operates the butterfly valve opening in front of the slides.
Kind of curious, since the time and expense swapping carbs will cost an unfair amount of both, and if the gain isn't worth the effort I'd rather put it somewhere else. :whistle:

Wonder if you outta write Larry Cavanaugh or APE etc (someone that really knows) and ask ...... modern carbs might be the way to go or maybe its not gonna be "like you say" not enough to make it worth while.

As I said before, a set of CV carbs might be better suited for my riding style. I go up and over the mountains to visit or on business. My 33's don't like high elevations and I'll be damned if I will stop and rejet each time.
Steve

swest wrote: As I said before, a set of CV carbs might be better suited for my riding style. I go up and over the mountains to visit or on business. My 33's don't like high elevations and I'll be damned if I will stop and rejet each time.
Steve

So the 33's are finicky things that work great in a consistent environment, when specifically tuned to it. But otherwise, they give grief?

CV carbs are more tolerant of altitude changes. You lose power at higher elevations and VM carbs become rich. That's one reason I've been trying to lean mine out. Besides, "lean is mean." :woohoo:
Steve