[Tbot]

My sister's 2005 750 has been sitting and rotting away in the garage for the last ten years or so. Long story short, it ran today. I rebuilt the Carbs (they were seized/frozen), new petcock..etc etc. I've read some of the posts on fuel issues but haven't resolved the issue yet. The vent line on the right side that attaches to the back of the right air filter ear thingee that comes from the tee is pissing fuel. At first I thought that line went some where and I didn't reassemble it correctly. Nope, that where it goes. The harder you hit the throttle, the more fuel pours out. I am so sorry I volunteered to get this bike running. Now all I want is thing out of my life. The vent line to the tank is not clogged ( I checked that after reading a post). Fuel cap checks out just fine (read that in another post). Beyond that, what causes the vent line to blow fuel? What will happen if I plug it? Will the engine starve and eventually shut down?

Next I'm going to install a longer hose and elevate it way above the tank and collect any $5/gallon fuel that tries to escape.

Suggestions, thoughts?

Note: Fuel gauge is not working. I'm assuming the float switch rotted away just like the petcock and has nothing to do with this issue.

 

[Spockster]

That's a vent for the carbs, it has to be open but not exposed to wind.

I would say one or both of the carbs has a stuck float or the float setting is too high.

Edit... Most likely a stuck float.

 

[Green1]

What type of petcock did you use? I honestly don't know how the "stock" system could get so much pressure, even with the float valve stuck completely (or even the float completely missing for that matter) to both run and pump fuel out that hose to the extent you describe. The vent hose attaches above the float chamber (and the carburetor fuel inlet) for fuel to be gushing out like you describe I am not sure the stock float valve could stop it.

The stock system is barely a step above a gravity feed and it sounds like your tank is pressurized. Since I have only recently began working on my carburetor and am trying to figure out it's quirks I am very interested in what it will take to get your's sorted. Keep us informed and good luck.

 

[Spockster]

There was a previous post about fuel gushing out of the right side air filter housing, but I'm not sure it would be easy to find.

Found one...

Gas coming out of air filter

Hello everyone I have an 85 vn750 and i have gas coming out of left side air filter I have drained the carbs put in some carb cleaner and let it sit for a few days then drained them again put in new gas it started right away (and it has never done that before)took it for a ride started out good...

www.vn750.com

Two ..

Gas streaming out of air filter!

hey all, I just replaced the seals in float bowls and jet housings on the carbs because their old and I noticed a gas leak coming from the bottom of the carbs. After I mounted them and put the petcok on PRI, after about 5 min, my air filter to the front cylinder (left side) was soaked and gas...

www.vn750.com

So far there's no conclusion, but in addition to the stuck float, there's a bad float valve or float that fills with gas.

 

[Green1]

Spockster, those are good posts to reference. If there is so much fuel it is filling the bowl completely and forcing its way out the vent I would expect problems with the filter(s) getting soaked as well. Plus I would be worried about fuel dripping down on the GB. Good memory.

 

[Spockster]

Spockster, those are good posts to reference. If there is so much fuel it is filling the bowl completely and forcing its way out the vent I would expect problems with the filter(s) getting soaked as well. Plus I would be worried about fuel dripping down on the GB. Good memory.

I'm finally recalling a post with fuel in the airbox, and a wet filter.

I would check for gas in the oil also.

 

[mmart]

I left my petcock open while in storage the first year, fuel filled the engine and came out anyplace it could. I thought I ruined the bike. Is there any chance yours is leaking and flooding the bike?

 

[Tbot]

Finally got back to this issue. Started bike and it wouldn't idle in addition to pissing fuel out the vent. I ran the vent line back the fuel tank just to see if I could figure this problem out without pulling the carbs again. No go, so I yanked the carbs and tore them down again. So far I've noticed that one of the floats is full of fuel. Hard to be a float when you can't float. I also found the jets clogged. Since the bike ran less than 20 minutes tops on those new jets, I'm sure the fuel tank has issue internally from being dry for so long and left to its own devices. So here's today question: In the carb bowl where the two jets are, there is a third brass stem with a hole in the center. It doesn't appear to be removable and the hole down the shaft doesn't appear to go anywhere. It looks similar to a jet. What's it for??? If a picture would help, say so.

 

[mmart]

I’ve never pulled these, but this guy goes through all the parts pretty well here:

 

[Spockster]

That might be the jet for the enrichment circuit (choke).

It's easy for the jets to clog in just about a month, due to the float chamber and jet chamber being separate. Jet chamber dries out quickly.

 

[Tbot]

That might be the jet for the enrichment circuit (choke).

It's easy for the jets to clog in just about a month, due to the float chamber and jet chamber being separate. Jet chamber dries out quickly.

Main Jet, Pilot Jet are on the left. What is the third brass fitting on the top right and do I need to worry about it? It is not removable and the passageway down the center is blocked. The carb cleaning vid doesn't mention it. Thanks in advance.

 

[Spockster]

View attachment 54585
Main Jet, Pilot Jet are on the left. What is the third brass fitting on the top right and do I need to worry about it? It is not removable and the passageway down the center is blocked. The carb cleaning vid doesn't mention it. Thanks in advance.

It's the jet for the choke.

 

[Green1]

I know that when I serviced my carbs I soaked them overnight in cleaner and hit every hole with both compressed air and canned carb cleaner to make sure no passages were blocked. There are passages that make turns in the carb body so that you cannot run a wire through them but air will clear out most obstructions. You can trace those passages by looking on the carb body where you will see raised portions that have been plugged by the factory "usually" with lead shot.

Professionals will sometimes open up these passages on rare carburetors while "restoring" them. I do not suggest this if you do not have a backup carburetor laying around. Rather just make sure the carb is clean and unless a small piece of sand or rubber is wedged in there, soaking in carburetor cleaner will do that. Hopefully a small piece of rust from the tank found its way into the passages and did not dissolve. Try and visualize the path the fuel follows from the tank all the way through until the vaporized mixture is drawn into the cylinder. When you blow out the passages push everything backwards toward the fuel inlet passages. Sometimes the small stuff cannot be pushed through the passage and needs to go out the way it came in.

(Sometimes I will filter the air coming out of the passages through a piece of white cotton when rebuilding carburetors so I can see if a plugged passageway is caused by rust, sand or perhaps a bit of rubber from something that is deteriorating elsewhere in the fuel system.)

You may want to add filters to the fuel lines after you replace the float(s*). *If one is shot the other may not be in great shape either. There are several threads about current methods guys are using to get rust out of their tanks and don't forget to dose a few ounces of Seafoam with every tank until you get a few hundred miles on it. Then add some just before you let her set for a bit. The Seafoam helps with the drying out issues.

 

[Tbot]

I know that when I serviced my carbs I soaked them overnight in cleaner and hit every hole with both compressed air and canned carb cleaner to make sure no passages were blocked. There are passages that make turns in the carb body so that you cannot run a wire through them but air will clear out most obstructions. You can trace those passages by looking on the carb body where you will see raised portions that have been plugged by the factory "usually" with lead shot.

Professionals will sometimes open up these passages on rare carburetors while "restoring" them. I do not suggest this if you do not have a backup carburetor laying around. Rather just make sure the carb is clean and unless a small piece of sand or rubber is wedged in there, soaking in carburetor cleaner will do that. Hopefully a small piece of rust from the tank found its way into the passages and did not dissolve. Try and visualize the path the fuel follows from the tank all the way through until the vaporized mixture is drawn into the cylinder. When you blow out the passages push everything backwards toward the fuel inlet passages. Sometimes the small stuff cannot be pushed through the passage and needs to go out the way it came in.

(Sometimes I will filter the air coming out of the passages through a piece of white cotton when rebuilding carburetors so I can see if a plugged passageway is caused by rust, sand or perhaps a bit of rubber from something that is deteriorating elsewhere in the fuel system.)

You may want to add filters to the fuel lines after you replace the float(s*). *If one is shot the other may not be in great shape either. There are several threads about current methods guys are using to get rust out of their tanks and don't forget to dose a few ounces of Seafoam with every tank until you get a few hundred miles on it. Then add some just before you let her set for a bit. The Seafoam helps with the drying out issues.

These are all good words and thoughts. I plan to purchase fuel filters to install on the lines to ensure clean gas gets to the carbs when I'm done playing with them. If I remember correctly, there's a screen on the petcock as well. With regard to my question about the third brass post ( Choke jet?); I hit the thing with carb cleaner daily for the last week. I can not trace where it goes. Is there a way to remove it without damaging the carb? When I initially ran the bike, the choke worked fine and this jet blocked even then. Since I failed to do this carb rebuild right the first time, I want to make sure I don't overlook anything this time. Taking these on and off the bike is a huge headache. Thanks.

 

[Spockster]

These are all good words and thoughts. I plan to purchase fuel filters to install on the lines to ensure clean gas gets to the carbs when I'm done playing with them. If I remember correctly, there's a screen on the petcock as well. With regard to my question about the third brass post ( Choke jet?); I hit the thing with carb cleaner daily for the last week. I can not trace where it goes. Is there a way to remove it without damaging the carb? When I initially ran the bike, the choke worked fine and this jet blocked even then. Since I failed to do this carb rebuild right the first time, I want to make sure I don't overlook anything this time. Taking these on and off the bike is a huge headache. Thanks.

I wouldn't attempt removing that orifice, it's probably staked in place and isn't part of a normal rebuild.

Try holding the choke plunger up while hitting the orifice with air and/or carb cleaner. If you don't lift the plunger, that passage will be blocked.