Carb/flooding issue

[sportpsyc]

This is the newer of the two GZ250's I have--an '06. I just got it running after it sat at the previous owner's for 7 months. It fired right up after I primed it, and ran fine for about 5 minutes, but now it is very sick. Gas is literally pouring out of the drainage hose (the one routed down behind the engine between the arms of the swing arm). It won't run, and is flooded. I took the carb off thinking the float was sticking, but it was clean and seemed to be working fine (he had drained all the gas from the carb when he stored it), and the needle was free and moving up and down with the float. I cleaned it all out good with carb/choke cleaner, reassembled it, and got the exact same thing. Is the gas coming form somewhere else in the carb? Is there maybe some trash I missed in the needle valve seat, or could it be something else from sitting so long? The gaskets looked good--not dry or rotted, and the diaphragm looks good--no holes and still soft. There wasn't any discernible gunk or build-up anywhere I looked, and the jets were great.

Any suggestions? I guess the good news is, I can take that dang carb off and re-install it in under 5 minutes now! :-)

[Easy Rider]

Gas is literally pouring out of the drainage hose (the one routed down behind the engine between the arms of the swing arm). It won't run, and is flooded.

Pretty much has to be a float problem of some kind.......since the function of that hose is to drain the excess when the bowl becomes over-filled. The other function is to drain the gas from the BOTTOM of the bowl when you open the screw on purpose. Any chance the PO drained it, forgot to close the screw again and you are really running out of gas instead of being flooded ??

If that's not the case, then there has to be something amiss with the float or needle valve. Could it be that the float is not "floating" anymore ?? WAY long shot is that the body of the carb itself is cracked and fuel is getting in without going through the needle valve.

[sportpsyc]

I'll take it apart and make sure there is no trash or gunk in the seat and on the needle. How the heck does that drain at the bottom know when there is too much fuel in the bowl? since the carb is gravity fed, I can't imagine it being pressure regulated. Maybe I'll check that out as well. The only other thing I can figure is that maybe the gas is coming from some where else in the carb and running down one of the jets. I'll check it out. THX!

[Easy Rider]

How the heck does that drain at the bottom know when there is too much fuel in the bowl?

If you've had it apart and still ask THAT question, then it's likely that you could have overlooked something else too !! :roll:

That outlet at the bottom has TWO inlets. It connects to an open tube that rises ABOVE the normal level of gas in the bowl. If the level gets above normal, the the excess gas spills into the tube and runs out. The OTHER inlet to the drain is slightly off to the side, drains from the bottom but is only open when the drain screw is loose.

This should be clear when you look at the inside of the bowl. :tup:

You didn't mention it so I will ask again: Is that drain screw closed ??
Please check that before you take it all apart again.

[sportpsyc]

Yeah, when I had it apart before, I just sat the bowl aside and focused on the float and needle, so I didn't remember exactly how it worked. I just went and took all the hoses off except the supply line, and saw where the problem is. I turned the gas on, and it is running out of the UPPER hose, listed in the manual as the "Air Vent Hose"" which is larger in diameter and comes off the upper right side up by the piston/diaphragm. So apparently, it isn't the float or the bowl. Got any ideas what the heck might be causing THIS issue? I am guessing something has trash in it, but where would it be to cause gas to come out of the air vent hose? I guess I really need to break it completely down and clean it, I just wasn't looking forward to having to buy any new gaskets or o-rings or a diaphragm.....
This reminds me how much I like direct fuel injection... ;)

[Easy Rider]

Got any ideas what the heck might be causing THIS issue?

Sorry. Don't know where that goes or how it could be leaking. :??:

Hopefully it will be obvious once you get it apart.
Please let us know what you find.

FI is nice but if/when it stops working, you can't usually take it apart and SEE what's wrong. :)

[jonathan180iq]

Are you talking about the vent line that runs from the top of the carb and looks like it hooks up under the gas tank/petcock?

When I was installing a fuel filter, I had the petcock set to PRI and the vent line disconnected. Until I plugges that line, the gas wouldn't stop flowing. It might be possible that the vent line has a flaw which allows air to seap in and is causing the constant running. Maybe you can replace that or at least inspect it.

It is a vaccum line which causes the fuel to be pulled into the system. If that vaccum isn't sealed, the result might be what you are experiencing.

[sportpsyc]

Now that you mention it, that might have something to do with it. The line I am talking about is the really large line that comes off the top and is pointed directly to the right side of the bike, BUT, the opposite side of that line IS where the gas comes in, and I noticed that it only pours gas out whe nin the PRIME position on the petcock. It still won't run even in the ON position, so perhaps it is a vacuum leak. Interesting thing, that vacuum line to the petcock--I thought it was gravity that got the fuel there, but I am really curious what role that vacuum line plays in the operation of the petcock and carb. I'll check that. Will the bike run with that petcock vacuum line plugged? Curious...

[Easy Rider]

I noticed that it only pours gas out whe nin the PRIME position on the petcock. It still won't run even in the ON position, so perhaps it is a vacuum leak. Interesting thing, that vacuum line to the petcock--I thought it was gravity that got the fuel there, but I am really curious what role that vacuum line plays in the operation of the petcock and carb. I'll check that. Will the bike run with that petcock vacuum line plugged? Curious...

We've been over this before.....at least the vacume part of it........Jonathan....... :roll:

The vacume line does NOT pull fuel anywhere....or push it for that matter.
Gas goes from the tank to the carb by the force of gravity........only.

What the vacume line DOES do is open a little valve inside the petcock and allow gas to flow in the ON and RES positions .......only when the engine is running and vacume is present. Or to put it another way, when vacume is absent, the fuel is shut off.

The PRI setting defeats this safety shut off and allows gas to flow even when the engine is not running.

After looking at the service manual, it appears that what I said before about the tube coming off the bottom was wrong. It is only a drain and not a vent/overflow.

Looks like the tube you are referring to IS, in fact, the vent and overflow so we are back to something wrong with the floats or needle valve. Can't be much of anything else. Although the inlet and vent hoses are right across from each other, I don't think there is any direct path for fuel between the two.......unless the body of the carb is physically damaged.

[sportpsyc]

Okay--good news. The problem is solved (at least mostly), and in the process I have discovered the greatest substance ever to find its way to a carbureted engine. I called an old man that lives not far from me, who is one of these guys who has ridden motorcycles for 50 years-literally. He confirmed that if there is gas running out of any part of a carb, into the engine or onto the ground, it can only be a float issue. So I cleaned the heck out of the needle and seat and bowl, and it fired up, but still ran like crap--wouldn't idle and was still flooding like it is running rich. But no more gas out the hose. So then the old man said--"wait and I'll be there and fix your problem." He had some stuff in a steel can called "Sea Foam". Siad you can get it just about anywhere (although I've never seen it!) We poured 4 ounces into 1.5 gallons in the tank. He said "go ride the hell out of it, because the problem is you have junk in the idle jet, and the Sea Foam will take care of any gunk or trash anywhere in the carb." I was a bit nervous about riding it since it sounded like hell and didn't want to idle, or to restart for that matter if it did die, but I rode it down the highway for about 10 minutes and came back, and kiss my butt, the thing is running like a dream. I have never seen anything like it. He said "yeah, I used to go through a lot of cans of carb cleaner, but I started using this stuff about 10 years ago and I don't think I have taken a carb apart since." Crazy. So, apparently, despite my best efforts to clean it out with carb cleaner, there was still some kind of issue with junk in the gas/carb.

Easy, thanks for the explanation of the vacuum line to the petcock. You are going to laugh, but I went and tried it--I put the long drain hose on the petcock vacuum line spur, took the main fuel line off, and turned on the gas. A little gas still did come out, but it was not a stream like when I turned it to PRIME. Then I sucked on the vacuum line I had put on it, and low and behold, the gas flowed free JUST like it was on PRIME. Good to know.

Thanks for all of you help and commentary. We'll see how it does after I ride it a while. I still need to see if it will idle worth a flip when it is cold.

[Easy Rider]

Then I sucked on the vacuum line I had put on it, and low and behold, the gas flowed free JUST like it was on PRIME. Good to know.


A grin maybe but not laughing.
That is actually the "standard" method of testing the thing but I NEVER suggest it by remote control because it can be dangerous to your health if you suck on the wrong tube at the wrong time !!! :cry:

Now, one more thing......maybe 2 !
Seafoam is good stuff for routine cleaning, when everything is OK or just slightly off. I use cleaner in one tank every spring just to keep ahead of any acumulating gunk. You might want to continue it for the next tankful or two since you have had a problem already. Seafoam is not, however, the best product on the market for heavy duty carb. cleaning.....but that's a subject for a different thread.

Without the engine running, there should be NO continuous flow in the tube going to the carb. NONE (except on PRI, of course). If there is, then the safety in the petcock isn't working right and you should get that fixed. If the bike is parked indoors and the needle valve ever sticks again AND the petcock isn't working right, you could have a very dangerous condition (house go boom)!

Glad to hear you are back on the road! :tup:

[sportpsyc]

Thanks--yeah, I am very happy I didn't have to take that damndable carb off again. And color me educated, becasue I had never seen Seafoam before, but It worked majic on this little Mikuni. I can't believe how much it affected it. It was explined that the problem was probably not grit or something visible like old gas turned to varnish, but rather scale that turns invisible when dry, but goes into suspension in the gas when it is wet, and blocks the tiny jet openings. I don't know, but I am glad it is healthy again. The more I ride it, the better it seems to get. I can see how if you used this stuff once or twice a year, you would never get enough build-up to NEED perchloroethylene or ethylbenzene (carb/choke cleaner). Again, thanks for all the help getting it going!