Bought a basket case gs500 for only $350! Please help

[joshyhunnid]

I recently bought a 2007 gs500f for the sum of 500 dollars. The catch was that it had some carb issues. It idled rough, and would die on throttle unless you set the idle to 4,000+ rpm. I thought to myself, "okay that should be fairly simple, the bike obviously sat for some time so the carbs are just gunked up." So I checked out the bike and made sure it ran and everything, and then got it towed to a friend's garage. I sprayed them out with carb cleaner and fixed a couple little vacuum leaks I found, aaaaaaaand nothing. The bike ran worse than before. So I did some research and eventually got overwhelmed and decided to take the carbs to a local shop to get them rebuilt and synced and everything just so I had some peace of mind. The shop informed me that there was a huge mess of problems with the carbs and that whoever rebuilt them last had no idea what they were doing, there were missing O-rings, one carb's needle was set super rich and th other super lean, the idle and main jet were switched on one of the carbs, they were way out of sync, the breathers were capped off, etc. So they just rebuilt them yesterday and I just slapped the rebuilt carbs on the bike and while it starts up MUCH easier and idles a little smoother, it still dies on throttle and another problem has emerged....

1. Sometimes when idling, the bike has this.... I don't even know how to describe it, almost like clanking/thunking/harsh tapping noise coming from what I believe is the left side of the engine. and every time this noise occurs, it is accompanied by some kind of clicking (near the carbs/back of engine). This noise also is accompanied by the bike stuttering and the idle dipping down and then settling over and over until the noise stops. I do not think it is valves because it does not follow the engine speed, it just happens once or twice then stops, and then again, and again, and etc. The weird thing is, sometimes it does not happen at all when I idle it.

2. when I inspected the spark plugs to fine tune the mixture, and one of the plugs looked fairly normal, while the other was black and sooty. there was also some black gunk around the edge of the plug that was wet. The plug smelled of gas so I am assuming one cylinder is too rich, and the other may be too lean or normal...?

3. When I am starting the bike, I usually need to turn it to prime for about 6 seconds, then back to on, then I can put the choke on and start the bike, is this normal?

I already have an inline fuel filter and the fuel looks normal and clean, no rust or flakes. I am thinking I should check for vacuum leaks and figure out the mixture as far as next steps go, but I am concerned about that clunking and was wondering if anyone had a good place where I should start with this mess.

Thank you all so much in advance, and please take it easy on me, I am new to bikes and carburetors.

[ajensen]

The Buddha is the wizard of carbs. However, I'd also check the valve clearances. When I first got mine, February of this year, the valves were too tight. Getting them right solved half the problem. The other half was solved when I went through the carbs. Good luck-it seems that you got yourself a really good deal on your bike. I hope it works out for you. GS500s are fun to ride.

[joshyhunnid]

The Buddha is the wizard of carbs. However, I'd also check the valve clearances. When I first got mine, February of this year, the valves were too tight. Getting them right solved half the problem. The other half was solved when I went through the carbs. Good luck-it seems that you got yourself a really good deal on your bike. I hope it works out for you. GS500s are fun to ride.

Okay I'll look into it, do you think that could be a cause of my clunking?


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[mr72]

Get rid of the in line fuel filter and recheck float heights and float needles. If it requires prime to start that's low floats, will also cause stumbling off idle.

Go find my blig post about fixing these carbs. Don't spray carb cleaner on them ever again. The shop likely didn't know what they were doing.

[Joolstacho]

For a start, your starter clutch is stuffed... next!... You're going to have to go through each of those symptoms to fix each one.

[joshyhunnid]

For a start, your starter clutch is stuffed... next!... You're going to have to go through each of those symptoms to fix each one.

My starter clutch? Why do you say that?


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[Bluesmudge]

I've had the starter clutch problem too. Thats most likely what you are hearing clunking on the left side of the engine on startup. If you let it go like that too long it will eventually come completely loose and lock up. Best to open the left side engine cover and see what is loose.

Here is my post for awhile back about what happens if you just ignore the problem:
http://gstwins.com/gsboard/index.php?topic=68907.0

If its still in the beginning stages you may just have loose bolts holding the starter clutch and generator rotor together. Tighten then up with some locktite on the threads. If it looks anything like mine you need to replace the starter clutch and check/clean the sump for all the metal particles created. Replace all gaskets of any engine covers you remove.

[joshyhunnid]

I've had the starter clutch problem too. Thats most likely what you are hearing clunking on the left side of the engine on startup. If you let it go like that too long it will eventually come completely loose and lock up. Best to open the left side engine cover and see what is loose.

Here is my post for awhile back about what happens if you just ignore the problem:
http://gstwins.com/gsboard/index.php?topic=68907.0

If its still in the beginning stages you may just have loose bolts holding the starter clutch and generator rotor together. Tighten then up with some locktite on the threads. If it looks anything like mine you need to replace the starter clutch and check/clean the sump for all the metal particles created. Replace all gaskets of any engine covers you remove.

Interesting, I'll look at that. Thank you so much!


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[joshyhunnid]

Get rid of the in line fuel filter and recheck float heights and float needles. If it requires prime to start that's low floats, will also cause stumbling off idle.

Go find my blig post about fixing these carbs. Don't spray carb cleaner on them ever again. The shop likely didn't know what they were doing.

just read your blog post, and I just wanna say thank you for the in-depth explanation. From what I read, aside from it dying on throttle, my bike is actually idling pretty normally. It idles at 4500-5000 upon initial start up, and then I usually just turn the choke to half or off. When I get a chance to go work on it again I will let it warm up fully before messing with the choke at all and see if that has an effect on my throttle issue, and then dial in the mixture screws. Thanks!

Edit: Why is the in line fuel filter a problem?

[mr72]

just read your blog post, and I just wanna say thank you for the in-depth explanation.

You're quite welcome. Mostly I was trying to save myself some time in writing the same thing over and over here in GStwins.

From what I read, aside from it dying on throttle, my bike is actually idling pretty normally. It idles at 4500-5000 upon initial start up, and then I usually just turn the choke to half or off.

That's the normal cold-start behavior. It's supposed to do that. It will likely idle low even when set correctly while it's cold, until it gets fully warmed up, and I mean like 20 minutes of on the road riding. I just rode my bike today to work and then had to go downtown to pick something up then a 40 minute drive home ... It idled at about 1000-1100 rpm for the first half of my 25 minute ride to work. When I went to run my errand I rode about 20 minutes until I got into the stop and go in town and it was rock solid at about 1400 rpm. The engine temp really does affect idle speed.

When I get a chance to go work on it again I will let it warm up fully before messing with the choke at all and see if that has an effect on my throttle issue, and then dial in the mixture screws. Thanks!

The throttle issue is not likely related at all to idle settings (speed, mixture, etc.). It's most likely either fuel delivery (float level too low, a clog somewhere, sticking float needle valves, etc.), problem with the needles coming up from the main jets (slide sticking, damaged/leaking etc. rubber diaphragms), a gross vacuum leak (likely, causes the slides to not come up), or something like the needle/slide/washer/etc. was not put together right. What is happening is when you open the throttle it lets in a lot more air but not nearly enough more fuel to match, so it won't rev and it stumbles. The fuel comes out of the main jet by virtue of the slide moving up and pulling the needle out of the main jet. So the issue is either with that action of the slide, or with the actual fuel supply to the main jet being insufficient to run the bike faster than idle (like, clogged lines, sticking closed float needle, low floats).

Edit: Why is the in line fuel filter a problem?

Because it has a high probability of restricting fuel flow and may very well be the sole cause of your off-idle problem.

One other thing you will have to eventually check is that the petcock is not clogged and opens completely with vacuum. A bad vacuum leak could prevent the petcock from opening enough so you might just be burning fuel out of the carbs and that's it. Does it do this same thing on prime and also on run? If so, then it's not the petcock. If putting it on prime fixes it, then suspect the petcock or a vacuum problem with the petcock.

I can almost guarantee you have a vacuum leak or a dozen. You may have many other problems too. Sorry to say I had my own basket-case bike to work out, learned all this the hard way.

[Bargarabandit]

Did you find the issue with the tapping sound?

[joshyhunnid]

Did you find the issue with the tapping sound?

Yes I did! So it was a mish mash of a few different issues:
1 the chain needed replacing due to tight spots in it. so when you decelerate or get to certain rpms, the tight spots bind and creat a weird rattle.
2 the chain tension was also not set correctly, which made the first problem worse.
3. I think the carb was actually backfiring and misbehaving badly, eventually I took it to a carb shop and got it rebuilt.

I have since sold the bike to my brother, but just check the chain and make sure there are no tight spots, as well as the sprockets, and chain tension