GS850 Petcock/Gas/Firing Problems

[Anonymous]

This is a fantastic website, and I have dug thru the old Q&A to try and resolve my bike's problem, unfortunately to no avail. Here's what's up:

1980 GS850G, bought three summers ago, ran fine. Last summer, started finding gas under the bike when parked overnight, problem got worse as summer went on. Old Q&A said fix petcock, I rebuilt... worked for awhile but crapped out in the fall. #2 cylinder wouldn't fire until around 4000rpm. According to old Q&A, this related to petcock problem of gas going down vacuum tube attached to #2 and flooding the cylinder.

This spring, I changed plugs, oil, etc., as usual. Gas leak still there, but bike ran great with the exception of the #2 cylinder which wouldn't fire below about 4000rpm. At suggestion of old Q&A, I put an in-line shut off valve between petcock and carbs to stop the leaking and flooding #2. Petcock, by the way, is always set to "on", versus prime or reserve.

Now... I have no gas leaking on the floor when shut-off valve is closed... good. But when I open it, within about 10 seconds (motor not running), gas just pours out of the airbox, waaaay more than when I just had the leaky petcock, AND out of a small rust hole on the bottom of the #1/2 exhaust pipe. When I try to start it, there's so much in there that it blows gas out the back of the pipe.

Also, the bike won't start and run, just start and idle for 5-10 seconds, then die. I assume this is burning off the gas sitting in the carbs. When I open the shut-off valve to let more gas into carbs, it immediately kills the engine.

Cylinders #1 and #2 exhausts are warm after it tries to run, so #2 is now firing... good. But, #3/#4 exhaust pipes are cold. I checked plugs, all four are firing, so I'm guessing #3/#4 are not getting any gas. Don't know why...

So, I fixed two problems (gas leak and no #2 below 4000rpm), but now have a bike that pours gas when shut-off value is open, and #3 and #4 aren't working. I love this old bike, it runs fantastic above 4,000rpm when everything's firing, and I take good care of it. Can anyone offer advice to keep this old girl on the road?

Many thanks,

Jon

[frosty5011]

Sounds like floats might be stuck, or float valves stuck in open position if its getting that much gas. Also, what do the #3/#4 plugs look like when you pull them......wet?

It sounds like you should take carbs off and give them a good cleaning. Use the "carb cleanup" pages, they'll show step by step how to do your CV carbs.

Also, you should not be leaving the petcock in the "on" position. Make it a habit to only turn to "on" when riding. When you turn engine off, also close petcock.

They'll be people along shortly with better advice. Hopefully you'll be back on the road in no time.

[Anonymous]

Frosty,

Thanks for the input... I will hopefully take a look at carbs this weekend. Just to confirm the point on the petcock being "open" all the time for others who may wish to help out, I only have three options, "open", "prime", and "res"... I don't see where I can close it. Please let me know if I'm missing something.

The #3/#4 plugs... I put new plugs in about a week ago... when I took them out, after the starting and gas leakage problems, they were dark and damp, wiped them with shop cloth and they cleaned up fine. I just can't figure out how putting that shut-off value in the fuel line caused #3/#4 to stop running. Unless its just one heck of a coincidence. Prior to that, the bike ran great, above 4000rpm. Below that, it still idled, but #2 wasn't firing. So, I'd like to believe the carbs fairly clean, but will check 'em out.

Thanks again for the input... I appreciate it. Anyone else feel free to jump in!

Jon

[Anonymous]

If you have a stuck float you may be able to fix it without much trouble. What you'll need to do is turn off the gas and then drain the float bowls. Then take a metal bar and rap on the float bowls. I don't recall wether the float hinges are to the front or rear so tap both ends.

Cheers, Steve

[frosty5011]

Hey Jon,

You're right! You can't turn the original vacuum-operated petcock valve to "off".

I misunderstood your first post where you said you installed an additional in-line fuel valve between the petcock and carbs. I thought you meant you always left that additional one on "on".

Also, since you say the #3 and #4 plugs were dark/damp, then it's not a case of them not getting any fuel, but a case of them having gotten too much fuel and fouling.

I'm kind of new at this too - compared to some of the old-timers here on the site. So, bearing that in mind, my answer may not be the correct one; it's just where I, with my limited knowledge in this area would start. There's quite a few guys out there that, once they read this, will correct any wrong suggestions I make and help you on your way. Just have patience

[Anonymous]

Got' er fixed, guys. Many thanks, she runs like a dream.

Okay... I admit it. I put the *%&$(*$ shut off valve on the vacuum line instead of the gas, causing gas to simply pour into 2, over into one (bike tilted on kickstand), and 3 and 4 got no gas. Yes... I could now qualify as a special guest on the next Beavis and Butthead Moron-a-thon...

Anyway, I put the shut-off on the fuel line, closed off vacuum line with another shut-off since its not needed. I did clean the carbs... on number 2 cylinder, the pin out the bottom of the needle was stuck, wouldn't "bounce" in and out. So I cleaned and it works fine now. So it was worth climbing into the carbs even though the big mistake was my own.