33mm smooth bore carbs

each carb has that boss but #1 does not have a nipple drilled and fitted. #2and 4 have a vent hose and #3 is capped off. All 3 would serve the same purpose(vents). they must lead to the same place, common to each pare of carbs , so u only need 1 vent per 2 carbs. So #3 is capped. That’s the way it looks to me anyways, without taking them apart. And they ran good for me.
Describe your build and i may be able to suggest jetting.

beleave it or not I have them on a fresh stock 900 with a 4-1 header,a dyna s, I took it around the block last weekend and it road great except for the popping brought it home and tore carbs, boots off , resealed the boots with some honda bond from shnitz racing and capped that middle port off and it seems to run fine need to put new plugs in again and do some more adjust ments but when I road it last it sure seem to run like a bat out of hell, I don't know why every say's they're to big .

Sudco manual 4th edition (page 28 exploded view; page 29 parts) shows Mikuni VM33 Smoothbore carb part #63 002-646 N148.013 Vacuum Cap on #3 carb.

Am thinking this part #63 is a rubber vacuum cap that plugs a vacuum nipple, and is in the area in question underneath the return spring.

Will try to post a link from my pic file.
[see following posts]


But if my link fails, just Google an image search Mikuni 33 smoothbore which should return the following link. Then click on the first exploded view. This shows the same parts numbers and diagram shown in the Sudco manual.

Click > [url=http://images.google.com/images?gbv=2&ndsp=20&hl=en&q=Mikuni+33mm+smoothbores&start=0&sa=N
eit faisl]Mik33sb[/url]

Perhaps the nipple in question is intended to supply vacuum for a vacuum operated petcock.

Good Luck!

This is a double post.

Please continue to next post.

thanks that helps alot

I'm sure that is just the common name they use for that cap. it should be a vent though.
to find out . take the cap off while running . if it is a vacuum, the bike should run dif when removed.
it just doesnt make sence to have a vacuum on 1 carb only,in the same location as the vent on the others.
The float level should be 22mm to 24 mm. I would sugest running them at 22mm.. this higher fuel level will help with fuel responce at low rpm's(more fuel presure on jets). it will cause it to run richer, so u may meed to reduce the pilot screw.

when I road the bike with that unpluged it would not idle right, needed the choke to run now I have it pluged and it runs good.just a little tweeking it should be fine. thanks all

that would lead me to believe that it is a vacuum.
it seems odd to have only 1, but as long as its runnig well that the main thing.

BigBlockT wrote:

beleave it or not I have them on a fresh stock 900 with a 4-1 header,a dyna s, I took it around the block last weekend and it road great except for the popping brought it home and tore carbs, boots off , resealed the boots with some honda bond from shnitz racing and capped that middle port off and it seems to run fine need to put new plugs in again and do some more adjust ments but when I road it last it sure seem to run like a bat out of hell, I don't know why every say's they're to big .

:huh: Hi!
I also have a set of 33 smoothbore which I intend to put on a nearly stock Z1-R. Stock today, but plans are 1075 or 1105 Wiseco (10,25:1), pod air filters (KN?) and a Kerker or an old Yoshimura 4 in 1 I have. Any suggestion on jetting this combination? What jetting do you have on your 33's when riding stock 900?:huh:

I know its old but glad I found this