Mystery fuel leak... - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 11 (permalink) Old 08-10-2007, 09:12 PM Thread Starter
 
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Mystery fuel leak...

I have been riding since I got the carbs done, and everything has been great...Until last Sunday. I rode to church (15 miles) and when I got there, steam was rising all around me. As it turns out, I broke a hose clamp under the tank. Rode over to a buddy of mine's, lifted the tank, replaced the clamp, and rode home.

That night, the garage filled with the odor of gas (which permeated the house, thereby annoying my wife and daughter). I thought I had partially pulled one of hte fuel lines off of one of the carbs, but that was not the case. Monday night, I tried to find the source of the gas leak. It appears to be in the rear carb, and it initially looked to be coming from the coasting richener valve, as the drips seemed to primarily be from the lower screw on the cover. I figured that the lip on the rubber diaphragm had come out of the groove on the carb face when I reassembled it. So I pulled the cover, cleaned up the gas, and reseated the diaphragm. Note that it felt kind of tacky when I was placing it, but no more gas seemed to be leaking...Until that night. Again, the garage and house filled with the scent of gasoline. I went out and sure as shooting, the carb was still leaking.

Tonight, I had a chance to look into it, and the coasting richener area was more or less dry, but there were signs of dampness in the pilot air mix screw hole, down toward the throttle cable attachment, basically all of the areas circled in yellow on the attached picture. (Please forgive the blurriness)

Does anyone have an idea where the gas may be leaking from? I haven't seen any problems with the front carb. I would like to get this fixed fairly quickly, because this weekend promises riding weather, plus I really don't like keeping the bike outside. I already intend to replace the coasting richener diaphragms next week.

Thanks,
--Storm
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post #2 of 11 (permalink) Old 08-11-2007, 12:52 PM
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Any problems at all with performance? My first thought was that the whole carb is flooded, but if the bike's riding ok, then that's not it. Check the connections to the cylinder - sometimes you can get a leak there that'll "spread out" from that one spot.

Also, check your fuel line going from the petcock to the rear carb - it's possible it's got a crack in it from being moved around, and, again, you've got a single source leak from above all of your circled areas.

C
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post #3 of 11 (permalink) Old 08-11-2007, 08:39 PM Thread Starter
 
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Any problems at all with performance? My first thought was that the whole carb is flooded, but if the bike's riding ok, then that's not it. Check the connections to the cylinder - sometimes you can get a leak there that'll "spread out" from that one spot.
Thanks Cindy,

Its entirely possible that the carb is flooded. When I rode home from my buddy's (my wife drove her car), she was talking to our neighbor at the end of the driveway. I stopped and talked to her husband. I shut the bike off and we talked about 15 minutes. When I tried to restart it, it would not start. I wound up running the battery down and could not get it to start. (I think I need to buy an MF battery...) So maybe I did flood it. But why only one carb?

Quote:
Also, check your fuel line going from the petcock to the rear carb - it's possible it's got a crack in it from being moved around, and, again, you've got a single source leak from above all of your circled areas.
The fuel lines are new, I replaced them while I had the carbs off.

So assuming I have a flooded carb, what do I do now? Just try to crank it until it turns over?

--Storm
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post #4 of 11 (permalink) Old 08-12-2007, 09:51 AM
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Hopefully someone else can jump in here, but I'd start by draining the float bowl. I'm not sure what the next steps would be, or if that might be enough.

C
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post #5 of 11 (permalink) Old 08-13-2007, 09:50 PM Thread Starter
 
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Update: Mystery Fuel Leak...

Okay, I had a friend come over tonight with considerably more wrenching experience than I on motorcycles. We started by pulling the tank off, and I immediately noticed that the fuel level in the tank was about reserve. When I got her home last sunday, she had about half a tank. So, just about everything leaked out in the last week except the reserve.

We did a function check on the petcock (which was definitely on ON and not on PRI, and no fuel flowed. So what I don't understand is since there was no vacuum without the engine running, how did the entire remaining tank get sucked out into the rear carb? The front carb is showing no signs of gas leaks. If I understand the fuel system, and I think I have a basic grasp, even if the float on that carb got stuck, the only thing that could have leaked was the contents of bowl. The carb could not get any more gasoline from the tank if the petcock was in the ON position. Am I right in my understanding of this?

Unless someone has some idea, it looks like I'm going to be pulling the carbs again...And right before the heat breaks and the fall riding season...Sigh.

--Storm
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post #6 of 11 (permalink) Old 08-13-2007, 09:58 PM
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You are correct, without vacume a proper petcock will not flow gas.
You may be looking a 2 problems, 1 a sticking flote in teh rear carb, 2 a leaking petcock.

Chad Falstad "Hawk"
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post #7 of 11 (permalink) Old 08-14-2007, 07:10 AM
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Quote:
Originally Posted by storm16 View Post

Unless someone has some idea, it looks like I'm going to be pulling the carbs again...And right before the heat breaks and the fall riding season...Sigh.
Take heart in the fact that the more frequently you pull the carbs, the easier it gets. You can probably have them out, inspected, and back in in a day or so.

Oh, and I don't have any other ideas, sorry. Chad's probably right on target...although you checked the petcock?

C
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post #8 of 11 (permalink) Old 08-14-2007, 02:14 PM Thread Starter
 
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Take heart in the fact that the more frequently you pull the carbs, the easier it gets. You can probably have them out, inspected, and back in in a day or so.
I guess so...Of course, I'm going to have to re-drain the radiator and all that...On the plus side, I guess since I am pulling it apart again anyway, I will relocate the R/R...

Quote:
Oh, and I don't have any other ideas, sorry. Chad's probably right on target...although you checked the petcock?
I checked it last night, but I think it was at the reserve level based on the weight. I'm going to put more gas in it and see if it leaks tonight. Part of me hopes that it does, so I can rebuild it and get riding...I'd much rather rebuild a petcock than to pull the carbs again...

--Storm
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post #9 of 11 (permalink) Old 08-23-2007, 03:58 PM Thread Starter
 
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I thought I had an idea of what was going on with this fuel leak, but reading Cardinal Fang and jaytango's threads, I have to wonder now. But I wanted to bounce it off you guys anyway, since the cumulative amount of Vulcan wrenching is staggering.

The conclusion I have come to is that my petcock has been leaking for a while. This would explain the hard starting (mixture too rich) and some of the other things I have seen, like when I rev the bike, it takes its time coming back down to idle revs.

Okay, so I have a leaking carb, and it just so happened that I had a fuel float stick open, so fuel continued to flow, causing the leak that I started this thread over. So to fix, I need to buy gaskets or a new petcock.

Does this make sense?

Now I have taken the tank off and pulled the petcock off of the tank, but I have not disassembled it (after jaytango's thread, I'm almost leery to do so). However, I have been shopping around for the parts to rebuild. In talking to one of the parts guys at a Kawi shop, he really confused my basic understanding of the petcock.

What he said was that if the diaphragm (part 43028) was bad, fuel would actually leak from the petcock, and that since it was leaking through the fuel lines, that it had to be the fuel tap gasket (11009) or the O ring (92055A) that were worn...

Now my read of the diagram is that since the vacuum line plugs into the bottom of the diaphragm cover (16146), the spring (92081) keeps the diaphragm closed except when there is vacuum to hold it open, and a weak gasket or o-ring on the front side could cause leaks through the petcock.

Am I off base here or does the parts guy have it wrong?

Thanks,
--Storm
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post #10 of 11 (permalink) Old 08-23-2007, 06:27 PM
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Well, I just pulled up the diagram on Bike Bandit and...I dunno! It sounds like a reasonable explanation - nailed the first set of issues, but there was something else going on as well. Sure wouldn't be the first time. I do know that if you're gonna rip in to the petcock and replace gaskets, you can get a rebuild kit (complete with all the gaskets, o-rings, etc.) for about (I think) $15 off of eBay. I cleaned up Orleans' petcock taking that route - I musta missed jaytango's thread, but don't be afraid of the petcock!! A clean workspace and a place to put all those little tiny screws as they come out helps. Also, since you'll be replacing gaskets, you can shoot the whole thing with PB Blaster and that may help with the screw removal.

C
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