Gas in Airbox from Engine Breather Tube 82 1100EZ

[away_man]

I'm getting gas in my airbox, and after

1) removing carbs, examining all parts (which were clean, almost no cleanup required), and putting it back together

2) replacing carbs, firing it up, experience the same problem, cursing,

3) pulling carbs & airbox, re-installing carbs with no airbox, and firing with (fortunately- this time) a small amount of gas in a "test tank" (clean plastic bottle),

I found out that the gas is basically flowing as fast as the engine can pull it through the carbs, and right back out the top of the engine, through the breather tube that connects to the top of the airbox. We're not talking about a dribble here; I can have a quarter tank through the system and running all over my buddy's driveway in no time flat.

This is on a 1982 GS1100E, which ran fine when I purchased it late last summer. I let it sit for too long with a weak battery, and after I got a new battery in it, this problem showed up (had been sitting (sidestand) maybe a month/month & a half).

It fires up just fine, even after sitting all winter (no gas in the tank becuase it dumped it all on the ground the last time I started it). Even when I ran my last trial, with a simple bottle > fuel tube > nipple between carbs 2 & 3, and NO airbox, it fired right up and ran happily for a few seconds until it started dumping gas all over everything, from the aforementioned breather tube that comes out the top of the engine. Once the fuel starts gushing through that tube, the engine chokes out and dies.

This is my first bike, and my troubleshooting thus far has been helped through conversations with a fellow GS owner (he has 3 or 4 now, I think), and many informative posts here. Initially, I thought (mistakenly?) that gas in the airbox was typically because gas was flowing directly back through the air intake on the carbs. Question 1: Is it "normal" to have gas coming out of the breather tube, due to a carb or some other problem?

-I'm pretty sure my petcock is okay, it seems to function properly with the standard tests of prime vs. "on" vs. reserve when off the tank. I also don't suspect a petcock problem, because I got the exact same symptoms with my "test tank" (see above).

-When I went through the carbs (first time I've ever gone through carbs, although I'm very used to taking things apart & re-assembling them), everything looked clean & happy. I *did* replace the o-rings on the needle valve seats; the old ones were a bit brittle & flat-looking. My needle valve seats had small screens on the bottoms, which were clean, but I don't see them in the pictures in the excellent carb dissasembly guide from this site. Question 2: Anyone know why that is?

-The floats we intact (no cracks), and nothing seemed to be stuck or clogged.

What I did *not* do when I went through the carbs was fully dissasemble and dip, and did not go through all the air channels with cleaner. I ran a wire through all holes in jets & needle valve seats for good measure, but I didn't find anything that warranted this.

The plugs on the air adjustment screws are still in place, which would lead me to believe these screws have never been removed/adjusted. (right?)

Okay! Question #3: What's Next? I'm ready to pull the carbs again and fully dissasemble & dip if necessary, but I'm not sure what I'm looking for.

One more question, and I'll quit typing, and go to bed. I called a local bike shop (whose mechanics strike my as knowledgeable, with lots of real-world experience, and who appreciated that my 1100EZ was fully stock when I got my safety inspection), and the first thing they suggested was a compression problem. Does this sound like a possibility, or were they grasping at straws, because it's a Yamaha shop, and I have an 82 Suzuki?

(sorry for the very long post, but I'm hoping that if I give y'all lots of background, I'll get lots of help. 8-[

[mcycle-nut]

Sounds like you have a serious needle and seat or float problem. Did you check the float hight? Do the floats still float?
When I bought my EZ, the guy said #1 cylinder will fill with gas if you left it on the sidestand. "How long is long?" I asked. "A couple of weeks," he said. Try overnight. :? A new needle and seat cured the problem. :-D Yes, I know you should replace all four, but hey, only one was leaking. If it ain't broke, don't fix it.8)

[SqDancerLynn1]

The tiny screens are fine. MAKE SURE YOU CHANGE THE OIL. Make sure their is no fuel in the vacuum hose for the petcock. Check the float level. The needles will probably need to be replaced

[dietcokeking]

Try this: Locate the vacuum line that goes to the petcock. Use a $2 hose pincher (available at any discount tool store) or similar to pinch shut that line. Put the petcock on PRIME and start 'er up. Any change in behavior? Mine was acting like yours. My petcock had a bad diaphram, which caused fuel to leak (or be pulled by engine vacuum when running) into the carbs/airbox thru' the vacuum line. I changed the petcock. That was five years ago, and the bike continues to run well!

Anyway, a carb float/needle would have to be stuck wide open to flow the amount of excess fuel you describe. A typical leaky float valve problem will usually seep, and not flood a running engine.

[away_man]

On the petcock operation:

When I tested the petcock (tank off the bike), fuel flowed freely in the Prime (3-o'clock) AND Reserve (9-o'clock) positions. Oddly enough, I couldn't get any fuel by applying vacuum when the petcock was in the "On" position (6-o'clock). Am I missing something here? At no point was I able to get any fuel into the vacuum line when I was testing the petcock.

(I'm assuming the nipple & line on the opposite side of the tank is just a tank vent, and has nothing to do with this problem.)

Another thought:
The "test tank" I used was something my buddy had, essentially a plastic funnel with a cap. When we filled it (maybe 20 fluid ounces?), it slowly drained down into the carbs, until it was pretty much empty before we started the bike. I don't recall if the cap was screwed on the bottle/funnel when we started the bike (I think it was), but the vacuum hose to #2 carb was open. Regardless, all the gas that we gave it ended up on the ground, after exiting the top breather tube. #-o Does this tell anyone anything?

I'm wondering if I re-created the issue in a different way, or created another issue when I used my test tank, although the amount of fuel that dumped out was similar to what happens when the real tank is hooked up.

I really appreciate all the help and advice here; I'm not experienced with these things, but thanks to y'all here at GSR, I'm learning quickly!

-Aaron

Oh, and I will DEFINITELY change the oil & filter before I ever put the bike in gear; I just want to get this resolved so I don't waste four cases of oil by dumping gas into it. :???:

[smithbm]

Does the fuel come out of the airbox with the engine not running?

[away_man]

I'm pretty certain no gas comes out when the bike is just sitting / engine not running.

[away_man]

After re-reading these suggestions, and thinking a bit, the issue is clearly not that the gas is being pulled through the petcock vacuum tube. I guess that leaves only a carb problem, then?

Can anyone else confirm the post by Dietcokeking, that a float problem in the carb would *not* result in the amount of overflow I'm seeing? I don't have a problem pulling the carbs again at this point, because the airbox is still off, but I'd really like to know what I'm looking for when I open them up again.

Any other thoughts from the experts? If so, THANKS in advance!

(bump)

[dietcokeking]

Can anyone else confirm the post by Dietcokeking, that a float problem in the carb would *not* result in the amount of overflow I'm seeing?

Just to clarify: It would not be the typical seeping problem past a float needle that is not seating properly due to wear or dirt. It sounds like it would have to be a major maladjustment of float height or a stuck float/needle. If you can eliminate the petcock as the problem (your temporary fuel tank seems the ideal way to eliminate the petcock while troubleshooting), you're gonna have to ask the carb experts here to offer advice. Still, make sure to pinch that vacuum line while you test with your temporary fuel tank.

By the way, have you tried leaving the bike on PRIME for a few minutes while the engine is NOT running to see if it overflows fuel (when it would not do so with petcock ON)? That would certainly point to a problem with the carb (whether the petcock was working properly or not). Remember to turn the petcock back to ON.

[kalessin]

On the petcock operation:

When I tested the petcock (tank off the bike), fuel flowed freely in the Prime (3-o'clock) AND Reserve (9-o'clock) positions. Oddly enough, I couldn't get any fuel by applying vacuum when the petcock was in the "On" position (6-o'clock). Am I missing something here? At no point was I able to get any fuel into the vacuum line when I was testing the petcock.

The proper operation of the petcock is:

PRIME: fuel flows freely even with the engine off (vacuum not needed)

ON: fuel flows only when the engine is on (vacuum is needed), except for the last gallon or so in the tank (the intake for this position is a little higher than the bottom of the tank)

RES: fuel flows only when the engine is on (vacuum is needed), all the way down until the tank is empty (the intake for this position is at the bottom of the tank)

Going by your description above, something's not right with the petcock, probably with the diaphragm. The vacuum part of the petcock can be disassembled without removing it from the tank. I'd suggest buying a petcock rebuild kit, drain the tank, work slowly and figure it out (and take notes as you go), it's not a difficult repair. On my old GS650GL, the petcock diaphragm failed while the bike was stored, and would flow gas without vacuum in both ON and RES positions (all over my friend's garage floor...), but it worked perfectly once i got the rebuild kit in.

(I'm assuming the nipple & line on the opposite side of the tank is just a tank vent, and has nothing to do with this problem.)

Suzuki put a drain on the side of the tank opposite the petcock in case the seal around the fuel sensor fails (which would be very rare, I think).

[BadBillyB]

After re-reading these suggestions, and thinking a bit, the issue is clearly not that the gas is being pulled through the petcock vacuum tube. I guess that leaves only a carb problem, then?

I don't have a problem pulling the carbs again at this point, because the airbox is still off, but I'd really like to know what I'm looking for when I open them up again.

Pull the carbs off the motor, stand them straight up on the bench and reconnect your test tank. Now you can see where the fuel is coming from, unless the problem is with the petcock.......BadBillyB

[rgierer]

Your carbs are clearly doing very weird things. Any new news?

[away_man]

Update:

No love. Put the carbs on the bench with no bowls, held the floats by placing the proper diameter rope between them & the lneedle valve seat clamp, and put some gas in the inlet tube via my test tank.

Results: Nothing. Not a miniscule little drip. Went to each carb (they're still assembled as a unit of four), removed the bit of rope that held the float up, and--Gas! Raised the floats again, No Gas! Almost as if it were designed to work like that. (Instert "sarcasm" smiley here)

Drained the gas from the carbs, then pulled each of the floats and checked to make sure they were floating. Yep. Sure enough, drop 'em in gas, push 'em under, and they pop back up, just the way they should.

Considering my bike ran fine before it sat for a month or so (although maybe a bit thirsty?), and I never opened up the carbs before it started dumping gas everywhere, here are the possibilities that I have narrowed it down to:

1. My floats magically adjusted themselves way, way off, to allow gas to flow freely when the engine is running. I haven't measured the float heights, but barring magic or miniature bike gremlins, there is no way they should be any different than the last time I started the bike when it didn't puke everywhere.

2. This issue is caused by something other than the carbs. The Yamaha shop I talked to suggested a compression problem. I have no clue what else it might be.

Can anyone help? I'm really out of ideas at this point, and I'm pretty sure my buddy is tired of having my dissasembled, gas-covered bike parts all over is garage.

[dietcokeking]

I can't imagine any circumstances where a compression problem could cause gasoline to run out of the airbox when the bike had been running well a month earlier! Make sure the petcock is not the problem. Pinch that vacuum line thoroughly, then run the bike on PRIME. If the problem isn't apparent on PRIME with the vacuum line pinched, then your petcock is the problem.

[Road_Clam]

Fuel is entering your airbox. If in fact you have a bad needle and seat, fuel will flow out the overflow vents. You observed no leakage bench testing your carbs. That rules out fuel leakages. How about raw fuel being "back blown" into the airbox from the venturi(s)? Does your bike currently run? I believe if you have a bad intake valve, that can cause compression backpressure, resulting in raw fuel being reversly pushed through your intake tract into your airbox.