Topic: can't get fuel to float bowls

[cbcoker]

my '72 cb350f doesn't get fuel to the bowls. i've cleaned the tank, petcock, put new fuel lines and cleaned out the carbs. still nothing in the bowls. i've adjusted the floats to within specs but need fuel in the bowls to run. is it likely there is a vapor lock issue? i did kreem kit the tank so its possible i coated over the vent tube. what else could i try? is there anyway to force fuel down into the bowls? i have cleaned the carbs very throughly and don't believe that there is any gunk clogging up the passageways within the carbs but i'm not getting any fuel in any bowls. i don't know what to so and any advise will be considered . thanks

[nickjtc]

Possibly a silly question, but did you dis-assemble the petcock from the tank before you kreemed it?

[KB02]

If you pull the hose off the petcock and the open the petcock up, does fuel flow out?

[750goes]

Start from the top and work your way down...
KB02 comments , take off fuel line from tank turn on petcock - fuel out ... yes or no???
if yes move to next logical place that fuel should flow to....
if no .... clean out the petcock
if still no flow....
clean out the tank it must be full of crud...or kreem...

[cbcoker]

First, yes i removed the petcock before kreeming the tank.

Second, I'll try blowing compressed air through the fuel lines and into the carbs. I've tried setting the float bowl height but it doesn't seem like the adjustments do much. By that I mean, the tang can only be moved so much. I have replaced the fuel needle within each carb that contacts the top of the float bowls.

Third, yes if I remove the fuel line fuel does flow out of the tank.

Fourth, everything has been cleaned and reinstalled from the tank on down. I'm going to try using the compressed air through the carbs, reinspecting float bowl height and then opening up the float bowl drain plug and turning the petcock on. Hopefully, after some fierce kickstart action some fuel will flow out of the bowls. Hopefully...

[TwoTired]

It is a gravity feed fuel system, kicking the bike won't matter, either with the kick starter, or elsewhere on the bike.

I don't know what your floats are made of.  But, I've seen compressed air damage the brass ones.

Can you install the floats upside down on the 350?

[Bob Wessner]

Another thought, when you replaced the fuel lines, did you install in-line filters? Are they pointing (flow direction) the right way? Sorry if this seems insulting, certianly not meant to be.

[cbcoker]

Yes, I put the inline filter in the right direction and its not insulting because I've probably made that mistake before. I would kick-start the bike thinking that turning the engine over would create a vacuum that might draw fuel into the bowls. I agree that brass could easily be damaged by compressed air and will remove the floats before shooting. So I take it that the fuel travels into the carbs and then simply drains into the bowls via the small holes directly above the floats. You could install the floats upside down but doubt that is an issue. I will double check.

[TwoTired]

Turning the engine over will create a partial vacuum on the carb throats to draw fuel from the jets, which are fed from the float bowls.  The float bowls are vented.  So, the kick start will not make suction on the fuel line.

Since you installed a fuel filter make sure that gravity can make a constant fall for the fluid.  Long lines with loops in them can trap an air bubble in them and stop flow.

The float bowls fill from the float valves when they fall away from their seat.

Um...did you install the fuel feed lines to the bowl vent nipples? Just checking...

[cbcoker]

I believe that the fuel lines are a direct as possible. As for installing the fuel lines to the nipples well no that isn't a problem as then I would need for separate fuel lines instead of two. Maybe the problem is in the float bowls because none of the cylinder are getting fuel. At least its consistant. The floats are installed so that their rounded edge is facing down into the bowls, correct? The bowls rest atop that tee shaped piece of metal that is attached to the main jet. Everything, I believe, is attached correctly it is simply a matter of the bowls being not adjusted or the valve needle not metering fuel properly. Something is not allowing the fuel to pass into the bowls. Before, I had a problem with fuel leaking from the connection between carb one and two, but I fixed that and not it is as if no fuel is reaching the carbs. argh.

[Bodi]

The floats go in curved side up, flat towards the bowl. How did you check the float height to the curved side?

[KB02]

The floats go in curved side up, flat towards the bowl.

Are you sure on that?

[Bodi]

Yes.
I scanned a picture from the Honda shop manual showing setting the float height - clearly showing the flat side facing "out". I tried to post it, didn't realize I have to host the image and provide a link.

[Zip]

As far as kicking goes, I turn on the fuel, do two kicks with the key off, and then she usually fires on the next kick.  This is only necessary after she has been sitting overnight.

Zip