Another intake issue

[maxpower_hd]

Hello all. I am new to this forum but not new to wrenching or GS's. I no longer own a GS, in fact I haven't had one in years. However, a friend of mine has a 1979 GS750L that I have inherited the responsibility of maintaining since he is wrench illiterate.

This one is completely stock with the original pipes, airbox, etc. It was tuned up this past spring and has been running fine. It has suddenly started sputtering and running poorly, looking to me like some sort of carb issue. The first thing I did was spray the intakes with starting fluid (I know, it's all I had) and found one boot where the motor will die out when I spray it and it has the original crappy philips screws that look like they haven't been removed in a long time. So far it just sounds like o-rings to me but I have one other issue to add to the mix. I also have fuel coming out the petcock. I was told this started at the same time. I'm thinking it needs a rebuild or a new petcock as well. Since it's very hard to turn and I've already had it apart once a couple of years ago, I'm thinking I should just go with a new one.

Does this sound reasonable to you folks? Any comments or suggestions on other things I should check? I was looking at the universal petcock and adapter plate in the following link to save some money. Has anyone used one of these? https://www.partsnmore.com/cat_index...&category=carb

Thanks in advance for any advice you can offer. It has been a while since I've worked one of these old girls.

Dave

[mark]

If the petcock is messed up, you might be sucking fuel into the bike through the vacuum line and that could "suddenly" cause your problems. You can suck on the vacuum line or apply some sort of vaccum to it. If you get gas through it, that needs to be fixed. They make petcock rebuild kits or you can just get a new OEM one. Pingel makes one that a lot of guys on this forum like, but you have to remember to shut it off when you shut off your motor. Don't know anything about the universal one you are looking at.

The O-rings are pretty much a standard maintenance item on a bike that old. If they've never been replaced, they probably need to be. Check the intake manifold boots for cracking or pieces that have "chipped" off. You can use water or WD-40 or something like that to test, starter fluid seems a little dangerous to me. Changes in RPM indicate a probable leak.

[maxpower_hd]

Thanks Mark. I'll check the vacuum line tonight. I would like a new petcock but I will rebuild this one if I have to.

Thanks again,
Dave

[bwringer]

I would also consider the petcock to be another standard maintenance item -- replace it and forget about it for another 20 years or so. It's well worth the money.