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General Category >> Rubber Side Down! >> Gas leaking out of the carb Help please
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Message started by beanprofit on 07/01/09 at 18:24:33

Title: Gas leaking out of the carb Help please
Post by beanprofit on 07/01/09 at 18:24:33

Hello all,
I have a 87 LS650 that I am trying to get going. It occasionally dumps a bunch of gas out of the carb vent tubes. I figured it might be a problem with the float valve so I took the carb apart and replaced the valve, valve seat, and O-ring. In general it looked in pretty good shape. After putting it back together it still does the same thing. What else is there that would cause this problem? Is the vacuum petcock actually supposed to let different amounts of gas through depending on RPM? Or, is it strictly a on off thing? When I have tank off the bike it does not leak a drop in the on position but when I run the bike too much as is getting in the carb.
Any ideas would be greatly appreciated.

Title: Re: Gas leaking out of the carb Help please
Post by serowbot on 07/01/09 at 18:33:38

If the vacuum diaphragm in the petcock tears, gas will enter the carb and engine through the vacuum line, bypassing the float bowl...
You need to check the vacuum line for the presence of gas... There should be absolutely none... ZERO!...
That is the line going from the back of the petcock down to the right side of the carb, usually covered with a spring.
You find any gas at all in there, and you found the problem...

Chances are 100% there's gas in there.

Options are to replace with new, convert to manual, or replace with alternative (Yamaha Raptor 660 manual petcock. Convert is cheapest but most difficult, Raptor is easiest, stock replacement is easy but expensive.
http://www.ronayers.com/browseparts.cfm?SearchString=5LP-24500-01-00&adv=5&kw...
The Raptor is an easy bolt on fix. You will have to cap off the vac line at the carb. I put a screw in it.... rubber caps will rot away every couple of months and cause a vacuum leak.
As a bonus,... going to the Raptor makes tank removal much easier too. No more wiggle jiggle... ;D

Title: Re: Gas leaking out of the carb Help please
Post by beanprofit on 07/01/09 at 18:38:27

There is no gas in the vacuume line. None at all. Do you think the float could be sticking open? if so what would it stick on?

Title: Re: Gas leaking out of the carb Help please
Post by beanprofit on 07/01/09 at 18:42:09

When it leaks gas it leaks in a big way. It will be ideling worse and worse so i'll rev it a bit and a half cup or so of gas will spray out the vent hoses in a matter of seconds.

Title: Re: Gas leaking out of the carb Help please
Post by tcreeley on 07/01/09 at 18:48:03

I had a similar problem on a suzuki GN400. There was rust in the tank that was getting through. Everything was fine, then some rust would enter the float chamber and keep the float from closing and the vents would overflow. I couldn't believe how little it took. I added an inline gas filter that picked up the rest of the rust and fixed the problem.

I don't really know this carb/petcock yet- my manual says leave the petcock in the on position when the bike is turned off. If it is in the off position gas can flow into the carb and into the crankcase. I had to break my habit of switching the gas off.

Good luck TC

Title: Re: Gas leaking out of the carb Help please
Post by beanprofit on 07/01/09 at 19:10:24

The tank is pretty clean but i'll try throwing a filter in there. Just to make sure what way does the float go in? It is possible to put the float in upsidedown and get the float bowl on. If i have only the bowl off I can see the solder joints holding the floats on. The tang is bent twards the valve.

Title: Re: Gas leaking out of the carb Help please
Post by verslagen1 on 07/01/09 at 19:27:26

I think someone had this problem when their jet was loose

Title: Re: Gas leaking out of the carb Help please
Post by serowbot on 07/01/09 at 22:56:16

Unusual,....
If it's not the petcock, it is something loose, or blocked up in the carb.
Just spraying or soaking the carb may not get it,... if passages are blocked up, use a small wire, (009, 010, 011" guitar strings work great),... to clear blockages...
Also make sure that your float will actually float,.... if it is leaky.... (pardon the pun).... You're sunk.....
Best of luck...
Keep us informed.
We'll all do our best to advise...

PS,... make sure that there is a brass washer under the main jet... and that your needle jet slide moves smoothly up and down...

Title: Re: Gas leaking out of the carb Help please
Post by beanprofit on 07/02/09 at 05:16:55

I think i may have figured it out but i have not tested it yet. Last night i was thinking about it and came to the conclusion that if the tank was not venting properly, the pressure in the tank may become great enough to blow gas past the float valve as the engine heated the gas. This explains all of my symptoms or randomly dumping large amounts of gas when the pressure builds up enough. So, i got up early before work this morning and took apart the gas cap. There is a little check valve under a welch plug in there that had a bunch of corrosion in it. The actual vent passageways are very small as well. So, I think it was in fact clogged. I give an update when I get it all back together tomorrow.

Title: Re: Gas leaking out of the carb Help please
Post by serowbot on 07/02/09 at 07:51:36

Hmmm,... never thought of that. I've heard of it causing fuel starvation, but not the flood. But when the gas expands, it's gotta' go somewhere...
Hope you got it.
Let us know...

Title: Re: Gas leaking out of the carb Help please
Post by beanprofit on 07/03/09 at 08:41:28

Well, It was not the vent. I tried running it without the gas cap on with the same results. I tried flipping the float over just for a sanity check and sure enough it did not work when it was in wrong (big surprise). I know the float valve seals because with even slight pressure on the float while blowing in the gas line no air gets through. Is there any part of the carb that could be missing of failed that would pull a vacuum on bowl and pull gas through the float valve? It only leaks when it is running even if I set the tank to prime. When I started it today without the gas cap on, it started right up, idled for a couple minuets, started to run rough, so I revved it up a bit and gas came spraying out of the vent hoses.

Title: Re: Gas leaking out of the carb Help please
Post by T Mack 1 on 07/03/09 at 09:03:27

Hmmm sounds like you looked at most of the common issues.

Me.... I would take the carb off and do a close look at the float travel to make sure it's not bent and rubbing something.

Title: Re: Gas leaking out of the carb Help please
Post by serowbot on 07/03/09 at 09:11:06

3136323D23213C353A27530 wrote:

Is there any part of the carb that could be missing of failed that would pull a vacuum on bowl and pull gas through the float valve?

Nope,... that's what the vent tubes are for.... to prevent vacuum in the float bowl.... and they aren't plugged because they are leaking like a mother...

Here's a thought,... set your petcock to prime, pull the vacuum line entirely, and cap the nipples at the petcock and the carb. Then run it and see how it goes....
You can just use an 1" of line with a screw in the end as a temporary plug,.... you must plug both ends...
Try it, for me....

Title: Re: Gas leaking out of the carb Help please
Post by beanprofit on 07/03/09 at 10:21:50

Ok, I think I fixed it (for real this time). I took the carb completely apart and cleaned everything and blew every thing out with the air compressor. I found a big lump of fine rust goo in that brass tube that the main jet screws into after I pushed it out. After reassembling I put a inline fuel filter in and took it for a ride. It ran great, backfired every once in a while (I think I have to mess around with the pilot screw now). I am still not sure why this solved my problem because float valve still should have stopped the flow of gas when the bowl filled up, but it seems to work now and the crap in the carb was definitely a problem. So, I think this is a classic case of rusty tank and junk in the carb. I plan to do a bunch of riding to day to confirm :).

Title: Re: Gas leaking out of the carb Help please
Post by beanprofit on 07/03/09 at 12:57:17

I took a 100 mile ride and it ran perfect!!! Thanks for all your help.

Title: Re: Gas leaking out of the carb Help please
Post by photojoe on 07/03/09 at 13:30:05

Feels good not paying a shop to do your work doesn't it?

When I first got the Savage, I had a serious belt chirp. My previous bikes had chain drives, so I really wasn't familiar with belts at all. Someone suggested a local shop, so I took the bike in. They looked at it for a couple of minutes and said "It's the original belt. It's shot and needs to be replaced." Cost? Around $300. Yikes. Point of information; The bike only had a little over 12,000 miles on it.

I read the forums and adjusted it myself. She's just shy of 20,000 miles, and the belt hasn't made a sound since I fixed it for free, with the help of a Clymer and members on this forum.