YACQ (Yet Another Carb Question), GS650G

[Anonymous]

Just bought my first bike, an '81 GS650G and am having carb issues.

Bike ran like a champ when I bought it and the only problem was some light tank rust. I rode it home about 75 miles and it ran perfectly.

Next day it wouldn't start. I checked checked the fuel valve and the gas that came out was red. I emptied the tank and the gas was quite red. I figured the carbs were clogged and so it wouldn't start.

I removed the carbs and had them "cleaned" at a local shop. Kreemed the tank. Put the carbs back on and went out for a long ride. It ran well, but my girlfriend said she could smell gas coming from the bike. On our way home the bike the bike stalled and simply wouldn't restart.

I took the carbs off again and noticed that the #2 float pin was "stuck" in farther than the others. Took the carbs back to have the guy check them out and he set the #2 float. He left them on a tank for a couple days and they didn't leak under gravity pressure.

Today I put them back on and it wouldn't start. I primed #1 and #4 and got it to start. Turned it off and it now it won't start again. I checked the plugs and #2 is completely wet with gas. Put in a new plug and got it to start. Shut it off, won't start. #2 plug is wet again. The other plugs are a nice light brown and appear to be burning correctly.

So after all that my question is, what would cause #2 to dump tons of gas into the cylinder, how can I figure out the problem and what's the best plan of action to fix it?

Thanks in advance for any help!

Chris

p.s. I should mention that when I brought it home the #2 plug was very rich, so the problem with #2 may have preceeded the rust problem.

[earlfor]

Although the carbs being hooked to a test fuel tank for a day without leaking shows the float needle valves to be working properly, it does not relate to whether the feul level height in the bowl is correct. Did your mechanic set float levels to specifications? Float level has a big impact on fuel flow.
Also, have the carbs been vacuum balanced? If balance is really far out of sync, you can get some strange quirks in startup and running.

Earl

[Anonymous]

Thanks Earl.

I am unsure about whether he set the float levels to spec, but I'm doubting he did. I'm positive they haven't been balanced since I bought the bike.

I'll bring up both things when I bring them back in.

Thanks!
Chris

[Detman101]

Re: YACQ (Yet Another Carb Question), GS650G

So after all that my question is, what would cause #2 to dump tons of gas into the cylinder, how can I figure out the problem and what's the best plan of action to fix it?

Chris

p.s. I should mention that when I brought it home the #2 plug was very rich, so the problem with #2 may have preceeded the rust problem.

Simple answer. Your Petcock diaphragm has died/gotten a hole in it.

My bike did the same thing when the petcock diaphragm holed itself. The bike was sucking in fuel through the vacuum tube that runs from the petcock to the #2 carb vacuum fitting.

Since switching to a simple on/off "Pingle" petcock I haven't had that problem ever again.

Good luck,

Dm of mD

[Anonymous]

Good advice. That is something even I can probably check!

If I apply a vacuum to the vacuum tube and get gas coming through the vacuum tube, then that would indicate the problem you describe?

Thanks
Chris

[Detman101]

Yes, just make sure you're not sucking on the tube with your mouth like I was. :roll:

Gas tastes real nasty...

:?
Dm of mD

[earlfor]

Its an acquired taste Damien. :-)

Earl

Yes, just make sure you're not sucking on the tube with your mouth like I was. :roll:

Gas tastes real nasty...

:?
Dm of mD

[Anonymous]

Did you buy it a couple weeks ago from a guy in Morgan Hill, CA? A guy, I might add, that knew of no problems or issues with the motorcycle, and sold it with good conscience and honesty? If so, that's me. If not, please disregard.

[Anonymous]

Yeah that's me. Don't sweat it as I knew the tank rust was a potential problem. I just hope that I can get it running again without too much of a hassle.

With the amount of gas that is in cylinder #2, I'm leaning (and hoping) that it is coming in via the pet-cock vacuum line.

If the floats are working correctly, is there any major drawback to capping the vacuum at the carb and the pet-cock, then running it from the prime position?

Thanks
Chris

[Detman101]

There shouldn't be any I don't think as long as the bike is running.
Someone else may chime in with more info on that.
I tried it for a short period before my Pingle Fuel-Valve came in. I didn't feel safe doing it though.

:?
Dm of mD

[Anonymous]

I have the old petcock from the old tank. The vacuum and fuel outlets are in different places, and prime doesn't work, but you might be able to use the diaphragm.
What's really strange is the red gas. I thought it didn't have that much rust in it. I had used 2 gallons of vinegar and 100 steel nuts to get the crap out. I rode it probably 300 miles total after putting that tank on. Of course I had no idea the petcock was messed up. If you want the old petcock, let me know, and I'll drop it in the mail to you. Cheaper than you coming down from Palo Alto.
In the meantime, you can cap the vacuum port on the petcock, and the line to #2, and use prime to ride it, but make sure you put it back to run or reserve anytime you stop, so fuel won't continue to flow with the bike off.
You're not trying to twist the throttle when starting it on choke, right?

BTW: Welcome to GSR.

[earlfor]

Its "if" the float needle valves are working properly that is the killer.
IF they seal 100% for 100% of the time, then no problem. Unfortunately, they dont. Even new ones can seep slightly. With a petcock, there is a vacuum shutoff and that is backed up with the float needle shut off. Prime position allows gas to gravity feed, engine of or on makes no difference.
A constant weeping of gas into the crankcase oil is not a good thing. I have had clutch linings become useless because of it and running engine bearings in gas rich crankcase oil isnt something you want to do. I advise against using the prime selection for normal running. I would resign myself to spending the bucks and buying a Pingel and the problem is solved forever. :-)

Earl

If the floats are working correctly, is there any major drawback to capping the vacuum at the carb and the pet-cock, then running it from the prime position?

Thanks
Chris

[Detman101]

I would resign myself to spending the bucks and buying a Pingel and the problem is solved forever. :-)

Earl

Quoted for truth!


Dm of mD

[Anonymous]

I have the old petcock from the old tank. The vacuum and fuel outlets are in different places, and prime doesn't work, but you might be able to use the diaphragm.
What's really strange is the red gas.

I think the big difference may be Summer in Morgan Hill (Hot and Dry) versus "Summer" in San Francisco (Cold and Foggy). When I arrived in SF, the tank was about a 1/3 full, leaving lots of exposed metal that would get tons of surface rust in a wet environment.

I would like the old pet-cock just in case. I'll PM you with my address.

Also, I thought I ran across "rebuild kits" for the pet-cock, but can't remember where. If they're available, are they recommended?

[Anonymous]

Thanks to everyone!

It is definitely the petcock. I capped the vacuum at the carbs and at the petcock and the bike starts right up! Time to change the oil and plugs and take it out for a ride

I didn't even have to suck on the vacuum tube. I removed the tank and gas was dripping from the gas side of the petcock. Once I capped the vacuum side, it stopped immediately.

I'll see how the old petcock works, or just splurge for a pingel.

Thanks again for all the help.
Chris