New to VM34 carbs and not understanding something...

[pnedac]

Thank you in advance for your help. I just am wrapping up my first build by myself and it has been one looong road. I started in February with a rusty barn find and now have a pretty sweet looking bobber. I recently switched the stock carbs out with brand new VM34 carbs. The rubber connectors from the carb to the engine have a nipple on each one that points down that the stock ones did not. What is it for and what needs to happen with it? I suspect that the tube coming out of the upper side of each of the carbs needs to connect to it but I am not sure that is really what it is. I am on the right track?

Also I have pretty much straight pipes with glasspacks and then they turn 45 degrees up and are cut. Could this, or the fact that I do not have any air filters on the VMs when I am trying to get it dialed in be causing it to not idle well? It idles either not at all or very high when I start it. I am so very close with this beast but I am facing these last few hurdles. I also was not exactly sure how the idle adjusts and how the main jet screw works with the upper springed idle adjust. I have read the Mikuni VM manual but it does not really discuss how to get them dialed in. I would have thought that this would be a little easier, especially with all new parts!



77 XS650 bobber.

Pnedac is strugglin' !!!

 

[weekendrider]

http://www.amckayltd.com/VM34-36.pdf

The barb on the intakes is a vacuum line? The ones I'm familiar with stick up and out.
Could be boots be on the wrong cylinders?

 

[5twins]

The tube coming out of the upper side of each carb is a vent and doesn't get connected to anything. It just vents to atmosphere. Your manifolds are mounted upside down and maybe on the wrong sides. The nipple on them should face up and out. It is a vacuum port used to power the vacuum petcocks on the later models. If you have plain old normal petcocks, just cap the nipple off. It must be closed off or it will suck air. If you've left it open, that may be why the bike won't idle. Here's another VM guide that may help .....

http://xs650temp.proboards.com/index.cgi?board=carbfaq&action=display&thread=730

 

[pnedac]

See? I knew I would be able to get some help on these things. I thank you for the info and will surely post up again once I have these things turned the right way and get them capped off! More to follow as I am not at work, but you can beleive that I will be checking that as soon as I get home. I knew that there was a reason for those brass nipples and I guess I just thought they looked like they shoud be facing down. I will cap them and see what kind of success I have.

Thanks!!!

 

[5twins]

Vacuum caps for the nipples can be purchased at the auto parts store. The 7/32" (5.55mm) size fits nicely but you should still retain them with a spring clip of some sort. If the bike backfires, it can blow them off .....

 

[pnedac]

What would happen if I filled the holes with gasket maker? Would that be a viable alternative? It seems to be it would be a nice little way to plug those suckers for good! Thanks in advance. I have the covers but I would like to simply get rid of the thought about the chance of them doing anything.

 

[5twins]

NO, no, no, you don't want to plug them for good. That's where you hook sync gauges to sync your carbs so they are very useful and desirable to have .....

 

[pnedac]

Good looking out 5Twins, I will make sure I just plug them with something removable. Here is the thing though, I see that yours go off to the side but mine stick straight up and the vlave covers are in the way so I either need to cut the brass piece down some or somehting. I can't seem to fit them straight on. Is it okay to leave the brass nipple facing straight down? The boots came with the new VM34s.

Thanks again for all the advice.

 

[5twins]

I think now you have the manifolds right side up but mounted on the wrong cylinders, lol. Switch them between the right and left sides.

 

[JR Hammer]

LOL.... brass nipples