Kawasaki Vulcan Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
Have some trouble with a fuel leak.
I bought a 2000 Vulcan 500 last summer and had a great time riding it. There was about a one week period in the fall where it was a bit too cold so I did not ride. When I started the bike after that week I noticed a small fuel leak. I decided to not ride and figured I would tinker with it over the winter, which of course didn't happen.
When I started the bike in the spring it started up pretty easy and the small leak started pretty quick. But after about 30 seconds of the bike running the fuel leak got very big. Dumping a pretty large amount of fuel out of the back of the airbox.
After a little internet searching it seemed the problem might be the floats. So I took the carb off but had trouble getting it open. I decided to buy a used carb off of eBay (said to be working fine). While I was waiting for the replacement carb I had a handy friend look at the original carb. He was able to open it up and his opinion was the floats were fine. Unfortunately he decided to take the jets out and mangled up the screw head. Since I already had the replacement carb I decided to put it on. When I started the bike it was the exact same problem. Small leak at first followed about 30 seconds later by a really big leak out of the airbox.
It seems odd that both carbs would have the exact same problem so I continued to search around on the internet. I found some people mentioning problems with the petcock. So I found a petcock on eBay (said to be working fine) and replaced my old one. Started the bike up and the exact same outcome as before.
At this point I am not sure what to do next. I do not want to take it to a shop because I know the repair will probably cost more than I paid for the bike! I also hate to keep buying parts that don't fix the bike.
My thought is to take the replacement carb off and open it up to see if it is a float problem. But the fact that both carbs showed the exact same thing and the original didn't have a float problem makes me have doubt in this. And some of you know how hard it is to get a carb off and on this bike!
So does anyone have any other ideas on what I what I should check/replace next? Any and all ideas are welcome!
Thanks for the help!
 

·
Registered
Joined
·
239 Posts
A bench test ....for testing carb internals, in your case float valves for their ability to seal seems to be called for, testing each one of your carb sets. I use a board and hang them on a metal tang device for EX/EN carbs on one end. Flip the board over and I have holding devices for 250 Ninja carbs. So my test board is doing double duty.

A remote, gravity fed fuel source and clear tubes (in my case translucent) enable you to test for basic leaks and, beyond that, working fuel levels in the bowls. Service manuals contain "float level" specs. This is set for accurate tuning.

The same fuel source and vacuum source could be used to "bench test" your petcock as well.

As I frequently work on carburetors, bench testing is a necessity for me....finding faults and enabling tuning tweaks prior to carb installation on the bike....saving many carb R & R (removal and replacement). As you've noted, carb R&R can be tricky....having to do it repeatedly, its frustrating. Much more efficient to find a fault on the bench, prior to re installation.

I bench test every set of carbs I work on...whether 250 ninja, 500....heck, I'm doing a set of 1974 CB550 Honda carbs later this week..the bike is not even in my possession.

Anyways my crummy pic will show the clear tubes....they will show the fuel level. The first pic is a good float level, in this case for EX500. The 2nd pic is clearly too high, needing both readjustment and a new float valve.

I consider float valves as consumables...never meant to last forever, I automatically replace with every refurb I do, as well as all orings and gaskets....items commonly contained in carb kits.

I think you'll find your float valves unable to seal...allowing full flow (when they should be closed) Hence your massive leaks.

Also note in this scenario...fuel can find its way into your crankcase, diluting your engine oil. This can cause bearing failure.

Closely keep track of your oil level during diagnostic period, until you get the problem repaired.

Sorry for run-on post.
 

Attachments

·
Registered
Joined
·
189 Posts
This sounds like the issue I had, where gas was flowing out by the air filter. You can see my thread here:

http://www.vulcanforums.com/forums/50-vulcan-500/229882-gas-overflow.html#post2480090

Basically, I tried all sorts of things, including working on the carb, but eventually I mailed my Carb to Ducatiman and he did a great job working on it and when I got it back, I didn't have sync it or anything, and it's been running great since.
 

·
Registered
Joined
·
697 Posts
Fuel flows from the tank through the petcock to the carbs, floats controlling if the carb bowls need more gas or not.
When not running there should be gas in the carb bowls.

IF floats not working you would have a leak with bike not running and the carb bowls would leak, empty.
Of course the carb bowls could leak into the engine, but then you would have starting problems, gas in the oil.

Having gas flowing OUT of airbox is not normal and the post about the tank not venting seems like a good idea.
Open the gas tank and run it and see what happens.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #6
Okay I finally had some time to work on the bike again. The good news is getting the carb on and off the seconds time around is much easier. Such is life. But the bad news is nothing has changed at all.
What I have done since the last update:
Tried running the bike with the gas tank open - same result.
Somewhere someone gave me the idea it might be the petcock so I changed that out - same result
Went ahead and took the carb off. It looked really good inside, like a recent rebuild had been done on it. Went ahead and took the floats off and checked them. No leaks. The pins looked new but I put in my new ones anyway. Put in new gaskets even though they looked fine. Check the float levels. One seemed to be a bit 'low' but not by much. Went ahead and adjusted it. Put the carb back on - same result.

When I stated it this time it started right up and ran smoothly for about a minute, maybe more. It then started dying out (probably the fuel building up in the airbox). After the first time it stopped there was still no fuel leak. I then restarted it but pretty much had to give it a little throttle to keep it going. After a couple times of that I had to give it a lot of throttle to keep it going. And then came the big fuel leak out of the back of the airbox.

So I feel like I am back to square one. Any thoughts or ideas on what I should try?
Thanks!
 

·
Registered
Joined
·
11 Posts
Discussion Starter #8
The carb vent line seems clear. Oddly I don't think I have ever seen gas flow out of it even when it is dumping out of the back of the airbox.

Couple of other updates and details:
The gas that came out appears to have some oil in it. I could be wrong be that is what it looked like to me.

I took the carb off (again) and opened it up. I do not know if this is a good diagnosis (or a good idea) but when I blew into the fuel line that comes from the petcock air would flow through when the floats were in the position they would be non floating. I then just turned the carb over and the floats went where they would be when floating I could not blow air through.
 

·
Premium Member
Joined
·
258 Posts
I took the carb off (again) and opened it up. I do not know if this is a good diagnosis (or a good idea) but when I blew into the fuel line that comes from the petcock air would flow through when the floats were in the position they would be non floating. I then just turned the carb over and the floats went where they would be when floating I could not blow air through.
By "non-floating" position, do you mean down as if the bowls were empty or all the way up like they were full? If they're up and air is getting in, you've got float needle problems. Being you said by flipping them over and you don't have air coming in, I take that as if the bowls were full. If that's the case and you get air coming in when they're down, that's how it should be :)

Down=needle open=fuel flows in

Just by what I've been reading, it sounds like maybe sunk floats? Too much fuel coming in and it overflows out
 

·
Registered
Joined
·
697 Posts
OK if you have fuel in the airbox, that would be before the carb.
Fuel doesn't get to that area.

IF a float isnt working -
A bad float would give the obvious problems of fuel flowing when engine off,
not starting,
bad idle / boggy throttle.

The question is how is it getting into the air filter?
 

·
Registered
Joined
·
11 Posts
Discussion Starter #11
By "non-floating" position, do you mean down as if the bowls were empty or all the way up like they were full? If they're up and air is getting in, you've got float needle problems. Being you said by flipping them over and you don't have air coming in, I take that as if the bowls were full. If that's the case and you get air coming in when they're down, that's how it should be :)

Down=needle open=fuel flows in

Just by what I've been reading, it sounds like maybe sunk floats? Too much fuel coming in and it overflows out
Yeah, its hard to find the right directional language here. To try and be clear, when I hold the carb upside down to its working position (so the floats are on top) and gravity pushes the floats down into the bowl (like we hope gas would push it up in the other position) I can not get air to flow through. When I flip the carb over to it 'correct' position and gravity pulls the floats downs, I can easily push air through.

So it seems to me the float pins can stop flow. And I do know the floats float when off and tested in a bowl of water (and show no leaks).
My next plan is to seal the carb back up and maybe use a squeeze bottle to force water or fuel in the fuel line and see if the floats and pins are working to stop the flow in that case.
Then if that works I might put the carb back on and hook it up to the tank and put it in prime to see if the floats stop that flow. I might try that clear tube trick on the drain nipple just to check the float heights that way too.

Assuming that all works, is there some way the pressure is building up so high that the gas can still get past a properly working float or find another way around? If so, what would cause that?
 

·
Registered
Joined
·
697 Posts
The gas tank and the carb floats only have the weight of the gas to deal with.
Dont use excessive pressure to check the floats.
And yes in any position of the petcock if the carb bowls are full and the floats are working the gas flow would be stopped.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #13 (Edited)
Another quick update:
I put the bowls back on the carb and put water down the tube that would normally bring gas from the petcock. With a little water I could still blow air through the tube. After a certain point I could no longer put water in and could not blow any air in. There was no water leaking out at that point. So unless this method is invalid for some reason it seems to indicate to me that the floats are floating and the float needles are sealing.
And yet gas still seems to be getting through to the air box in large amounts. When I take the carb off after one of the gas overflows you can clearly see that the parts of the carb that attach to the airbox are wet with fuel. So it is clearly getting through.
Is there any way that fuel could be getting through before the floats get high enough to stop it? Should I just crank the floats in a way so they cut off the fuel very earlier? In that case the bike would be 'lean' but should not leak, correct?

Edit: I just put attached the carb to the gas tank and put it on prime and tested the fuel height in a clear tube. It seems to come to about the right height, just below where the bottom bowl seals to the carb. It shows no signs of leakage when doing this.
 

·
Premium Member
Joined
·
258 Posts
Water is heavier and "thicker" than water, so fuel might still get through. Best to test with actual gas
 

·
Registered
Joined
·
697 Posts
Gas / water It"s all liquid you seem to describe it as all is working.

Try as you mentioned.
Set the float level so that the carb bowls fill to a lower level. re-install the carbs and see what happens.

The problem I see is the air is rushing into the carbs, so how does the fuel get out that way?
Are your carb boots, and especially the carb to engine ones, sealing good to the engine?????
 

·
Registered
Joined
·
11 Posts
Discussion Starter #16
Gas / water It"s all liquid you seem to describe it as all is working.

Try as you mentioned.
Set the float level so that the carb bowls fill to a lower level. re-install the carbs and see what happens.

The problem I see is the air is rushing into the carbs, so how does the fuel get out that way?
Are your carb boots, and especially the carb to engine ones, sealing good to the engine?????
The boots that connect the carb to the engine appear to be very good. One of the boots that connects the airbox the carb never seems to pull perfectly in place but I would still estimate it to be a pretty good seal.

Yesterday I hooked everything back up but did not connect the boots to the airbox. I wanted to see if I could see fuel coming out of that side trying to get into the airbox. The bike started but ran very weak and I had to keep the throttle down to keep it running (I am guessing this is because those boots were not connected) so it was hard for me to get a close inspecting while running. I managed to keep it running for 40-60 seconds and could not see any signs of fuel coming out that way. Things appeared to be dry on inspection. I went ahead and hooked those boots up and started the bike again and I was surprised how quickly it went to 'full leak mode'. Either a lot of fuel quickly went into the airbox on the second start up or fuel got into the airbox on the first start up. On the first startup the boots did overlap the carb quite a bit (it would be pretty hard for this not to be the case) so maybe some fuel was flying in there and just not dripping out? I don't know if there is any other way for fuel to get into the airbox. Is it even possible?
 

·
Registered
Joined
·
697 Posts
First - is the airbox empty - NO fuel in it? No corner, knook, where it could hide?
Second - and I dont know if there is such a thing, do you have a diagram of where each hose should connect to?

As your last post says it seems without the boots on no fuel was going the wrong direction, by that I mean all gas should go into the engine, so if a hose was one the wrong location and a vacuum happened to pull fuel into the airbox....

That's what is puzzling to me.
When the boots on and sealing you have a vacuum happening and no fuel should flow the "wrong" direction into the air filter.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #18
First - is the airbox empty - NO fuel in it? No corner, knook, where it could hide?
Second - and I dont know if there is such a thing, do you have a diagram of where each hose should connect to?

As your last post says it seems without the boots on no fuel was going the wrong direction, by that I mean all gas should go into the engine, so if a hose was one the wrong location and a vacuum happened to pull fuel into the airbox....

That's what is puzzling to me.
When the boots on and sealing you have a vacuum happening and no fuel should flow the "wrong" direction into the air filter.
I am not sure if there is fuel in the airbox at any moment until it starts to leak out the back. I am not sure how to check.

I have certainly wondered if I have put the hoses on in some wrong way to cause this. I do know I never had touched anything the first time this happened. I have looked up where the hoses are supposed to go and 'think' I have it right but just in case: I have the larger hose from the side of the petcock (fuel I think) going to the bottom 'bar' on the carb. I have the smaller line from the petcock going to the nipple on the left side (as you sit on the bike) of the carb. I have the smaller line that come from the front of the bike (vacuum switch or something like that) going to the nipple on the right side of the carb. I have the larger tube that just dumps out on the left side of the bike going to the top bar. I think that is all of them. See any errors in there?
 

·
Registered
Joined
·
697 Posts
Not sure what you're getting at with this -
"I am not sure if there is fuel in the airbox at any moment until it starts to leak out the back"

IF its leaking out the back, which I'm guessing is the airbox how is it not getting into the airbox??
If the airbox drain tube has fuel in it then it IS getting into the airbox.

No fuel should ever get into the airbox or drain tube. That is my statement of the wrong way.
The drain tube is for excessive oil and maybe water/condensation to drain from the air filter "airbox" area.
 
1 - 20 of 26 Posts
Top