Gas blowing out of exhaust.

[Guest]

So I've a '81 GS650L. Cleaned and put new O-rings in carbs and bench synced. Put new O-rings in intake boots. Gapped valves to 0.05-0.09 all the way around. Before I put tank and seat back on I filled carbs with gas with funnel. She started right up after five turns and ran great. I cept filling thru funnel and let it run for about 15 minutes as I adjusted rpm's to about 1100. Everything look and sounded great, so I put on tank and seat. Put new gas in, and started back up. Right away white smoke and gas started pouring out of exhaust. So much that gas (yes gas) was dripping off my hand. I moved petcock to all positions, with same result. So pulled tank to inspect of maybe I connected something wrong, but looked good. Without tank I restarted, there was no smoke and no gas out of exhaust. Put tank back on, white smoke and gas out again. Carb floats ate at about 22mm without gasket and specked to right hight. Petcock seems to function properly, at prime gas flows, run and res need vacuumed to get gas thru. I'm really confused, and have a wicked head ache form gas fumes. Has anyone had this happen, and most of all fixed it? Please point me in the right direction. Thanks for the look.

[chuck hahn]

Funnel nothing and tank is overflowing doesnt make much sense. seems it would do it regardless of the fuel supply. One thing thats for sure is a carb..or a few are over lfowing. Are the pilot jet rubber plugs in place and sealing good? This would allow a lot of extra fuel to be sucked up. That or stuck down floats are the 2 that immediately come to my mind.

[mljbone]

Thanks for the response Chuck. I put new plugs in pilots. Before I put the carb rack back in to air box and intake boots ( what a major pain in the you know what) I turned the carbs upside down and tried to blow air in thru fill tube, and couldn't. I figured that the floats were working. But it makes sence that gas is dumping into cylinders with wide open needles. Also I just noticed that the tank over fill is spewing gas. I guess I've one more day at this.

[derwood]

It sounds like the petcock has failed, fuel is getting directly into the carburetor through the vacuum line.
to prove this take the vacuum line off and plug it,( twice, from the petcock and to the carburetor) it should then run fine on "prime"

[tkent02]

Also I just noticed that the tank over fill is spewing gas.

Huh ?

[tom203]

Huh ?

Hopefully he's refering to tank sending unit drain hose.

[mljbone]

Yes the overfill hose from the tank. I pulled the carbs and going to double check the float height. And make sure the gaskets which I made aren't interfering with floats. But I did just turn the carburetors upside down and blew in to fuel input and no air when in. I'll plug vacuum line after everything is put back together I'll let everybody know how went. Thanks so much for the input it's greatly appreciated. I'll post a picture of the beast as soon as I figure out how.

[chuck hahn]

22.4 on the floats according to the chart. And get the tank sealed before it ever goes back on the bike. Often the gaskets start getting hard and shrink away from the sending units base. I have taken sending units out and found a bead of Ultra Black RTV around the gaskets. It does work but ideally you need the new gaskets.

And another thing that makes the sending unit leak is the wrong length bolts holding the catch cover on over the sending unit itself. Too long on the bolts and they poke holes in the tank.

http://members.dslextreme.com/users/bikecliff/images/carbspec_float_height.html

[tkent02]

Yes the overfill hose from the tank.

There is no such overfill hose. WTF are you talking about?

[mljbone]

It's an"overflow" hose. At least on Bikecliffs site undes "where do these hoses go". That what he calles it. I guess I miss called it an overfill hose. Anyway with less then a gallon in tank gas comes out of it. Thanks.

[mljbone]

So I pulled the carbs and replaced the new gaskets I made and with old ones. Just to make sure floats cant hang up on gasket. Readjusted floats to 22.1-22.4mm's. Plugs are perfect in bowl. Plugged vacumme line from tank, out of carb port and set petcock on prime. Guess what? No gas blowing out of exhaust. Filled tank, ran at idle for 20 minutes with mild smoke. But she ran great. Also no gas out of the "overflow" line from tank. I'll register and have her back on the road after setting for 12 years. Thanks for all the help. This is a work in progress, but it's been an nice adventure. Will post a pic when I figure out how. Mark.

[chuck hahn]

That smoke is a lot of gas and oil laying in then pipes thats gonna take a while to burn off. After a few days rirding a decent distance ( not 3 trips across town stuff ) like for a good 20 minutes or so a few times it should start clearing up.


IF after, say a week, and its still making oil type blueish white smoke, youre probably in need of valve stem seals . If it clear and reappears afteras few days sitting, thats also a tell tale sign of bad valve stem seals.