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Joined: Mar 05, 2007 Posts: 32 Location: Bells, Texas
Posted: Tue May 11, 2010 4:10 pm Post subject: 1980 GS750L Fuel
Any and All,
It's been a while since I've posted, but I have a question about the fuel delivery, ie., petcock, on an '80 GS750L. The fuel ports coming from the petcock, top and bottom, can someone tell me which is for vac and which is for fuel delivery to the carbs? I'm not getting very much fuel to the carbs, and was wondering if someone has a picture or on-line reference I can check, to make sure mine are in the right place? I'm ready to ride, but can't.
Joined: Oct 03, 2005 Posts: 1595 Location: Marshall, MI
Posted: Wed May 12, 2010 10:06 am Post subject:
Pretty simple really. The smaller tube goes to the vacuum on #2 carb and the larger ferrule goes to the fuel line. That is the way it is on my 81 GS850L anyway. _________________ You only go around once in life, but if you do it right, once is enough!
Joined: Mar 05, 2007 Posts: 32 Location: Bells, Texas
Posted: Wed May 12, 2010 12:27 pm Post subject:
Thanks Steve. By what you said, I do have them in the right place. Now, looking at it further, I now have fuel coming from the vac hose, out of the petcock. Would this be indication that the petcock diaphragm is worse than originally thought. Also, noticed that the fuel flow thru the filter is not adequate enough to put fuel to the carbs. I'm gradually looking at one thing at a time, and hopefully this is closer to why the bike won't start and run.
Joined: Oct 03, 2005 Posts: 1595 Location: Marshall, MI
Posted: Wed May 12, 2010 12:38 pm Post subject:
Yes, it sounds like the diaghram in the petcock is shot. Now, this petcock does have PRI if it is the same as mine. You can run the bike on PRI which is prime or gravity feed. Try that but sounds like a new petcock may be in order. You may have to buy the whole thing as a unit. _________________ You only go around once in life, but if you do it right, once is enough!
Joined: Mar 05, 2007 Posts: 32 Location: Bells, Texas
Posted: Wed May 12, 2010 5:12 pm Post subject:
I plan to either buy a new one or try to rebuild this one. Hopefully can get one or the other done sometime in the next week. Thanks for the help. I'll keep posting until I get it running.
you could try plugging the vacuum line off the carb and capping the vacuum portion of the petcock, set it to prime and see how it runs
if you have gas leaking into the vacuum line youll need to stop that first thing, even a small vise grip mid line to test it
also, have you pulled the petcock off the tank? theres a filter inside there, check that for flow issues, its a rubber gasket so it should reseal easy enough
Joined: Mar 05, 2007 Posts: 32 Location: Bells, Texas
Posted: Thu May 13, 2010 8:35 am Post subject:
I haven't tried plugging off the vac line. I took the petcock off and checked the filter and it was pretty clear. I did notice some grime around the seal where the petcock seals to the tank. It cleaned up pretty good. I'll have to do some more checking on the petcock later this week.
Joined: Mar 05, 2007 Posts: 32 Location: Bells, Texas
Posted: Thu May 27, 2010 4:09 pm Post subject:
Just updating. Put a new petcock in, got fuel to carbs and need to have them sync'd. Anyone know of a good way to do this with minimal effort? I don't have any sync tools or a way for fuel supply with the tank off. Also, anyone know of a good supplier for original or aftermarket seats? Doing some sprucing up now and need to get a new seat or have mine recovered. Also, gonna try and clean the engine with a steam machine to get into the hard places on the motor. All is looking better so far!!!
Joined: Feb 01, 2010 Posts: 45 Location: West Kelowna, BC
Posted: Fri May 28, 2010 9:19 am Post subject:
"or a way for fuel supply with the tank off"......
Buy a couple of feet of fuel line and vacuum line, plus straight connectors for each line size. Set your fuel tank (removed from bike) on a bench on blocks to raise it up so that the petcock is not resting on the bench, or, as I use, a Black and Decker-type work mate. Connect the fuel line and vacuum line from your engine to the petcock using your new handy-dandy fuel and vacuum lines. There yah go, remote fuel source.
If you doubt the integrity if the petcock vacuum, plug the engine vacuum line with a small bolt, and test run the bike on Prime.
Do all this kind of work outside or in a well-ventilated area...you will spill a bit of gas, even being reeeeel careful.
Regarding carb syncing, check out this link, which comes via the very excellent GSResources site, which I'm sure you're already familiar with, if you have a GS...if not, check it out!!! The link to that site is on the bottom of this link....
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