vm34 overflow pouring out

alright. I am running vm34s. I used them all last summer with no problem. yet as soon as I try them after my rebuild, i am having trouble.

first of all, i changed my fuel line routing. the line goes from the petcock to the right carb with the left carb tieing into the line at about midpoint. that make sense? i just got back from a bar....

On my right carb, I am getting a very heavy fuel stream out of the overflow port on the bottom of the carb. But, it only starts flowing when the fuel is about half way up to my tee in the fuel line. (between the carb and the tee)

the floats arnt sticking as the are pretty mich new carbs andf are clean and dont stick when i open the carb up.

is the added pressure of the straIGHT line to the caRBS forcing it to overflow?
Can that happen?
Why would a carb overflow if the floats are working properly?

The floats may be hanging up somehow, maybe against the bowl. Sounds like it's time to do a bench check...

TwoMany, a VM34 carbie uses a pair of separate floats that ride up and down on posts in the float bowl. The floats get nowhere near the sides of the bowls, and won't hang on the posts unless things are very nasty indeed. Pat, your carburetors would not overflow if the float system was in order. That can happen in earlier BS38's and similar carbs that vent through a pipe set in the float bowls if the seal at the bottom of the pipe fails, but your carburetors don't vent that way.

It's most likely that one of three simple things has happened, and none has anything to do with fuel line pressure. Either one of your floats has lost buoyancy and turned into a sink, or your float lever arms have been tweaked due to mishandling so that float level is too low (fuel level too high), or you have debris or varnish in the float valve that prevents the needle from seating.

I had exact same issue. I have vm34 carbs. I placed a water bottle to catch overflow overnight and it was just a little. My carbs are clean. Floats are fine. Set float level to spec. Still would overflow a bit. I had a leaky petcock. I placed an inline valve between petcock and carbs. Closed valve at night . No more overflow issues. Replaced petcock and have not had an issue.

Well I think I may have figured it out. I took the bowl off and when I blow into the fuel intake port and close the needle seat with my finger, air can still flow. Shouldnt happen correct? Same happens if I pour a small amount into the fuel intake using the sink faucet. So I believe my needle seat is clogged up.

Now, how the hell do I get that bugger out of there???
or is there a way to clean out the seat without having to take it out of the carb?

that is another way to find out is float plunger is working. Blast it with some carb cleaner. And retry. If it still let's air/fuel through when you push on it with your finger. You will probably need to get a new float valve.

use toothpaste and a qtip to lap the need seat and clean up the tip of the needle as well

Running any filters ?

No filters on mine...

RatyXS said:

Running any filters ?

Click to expand...

Thats what it was. I didnt have a fuel filter and something must have been clogging the needle seat. I ran the needle seat under a faucet with it still in the carb and it must have knocked the little piece of whatever out of there. It seals great now.

And I now have an inline fuel filter to keep it from happening again.

Thanks for the help everyone, this goes to show I am still an idiot haha

Glad you got it. The tiniest piece of dirt can do it..