What happened to my bike?

[Ringo]

I was out for a ride on my bike when it started to act weird. The revs dropped and the engine stalled. I pulled over and managed to start it again after a few tries. Then I drove about 500 meters and it would die again. Repeated the process a few times until it refused to start.

So I walked with the bike to a friend, which was closer than to my home. I left my bike at my friend's place for a few days. His neighbor came to look at it. He couldn't figure out what's wrong with it, but managed to start it by messing with the petcock. I drove to a workshop (bike died
a few times on the way) and let them have a look at it. They couldn't find out what the problem was either. But by that time, the bike was alright again. It started without any problems! The mechanic at the workshop said he cleaned the carburetor, but he doesn't think that was the thing which caused the bike to die. Because they didn't actually find anything wrong on the bike, and it worked fine when they rode it, I didn't have to pay anything

So, now my bike's ok except for one thing. It makes a horrible noise sometimes. It seems to appear at random, but only when the bike is warmed up. It's kind of hard to describe the noise, but it sounds something like gearwheels scraping eachother instead of meshing. The bike works fine and all, but that noise makes the ride rather unpleasant. It's also somewhat embarrasing when passing pedestrians

The noise started to appear when I left my bike at my friend. Any idea what it could be? And any ideas of what happend to my bike in the first place (that is, how it got ok by itself)? My bike is a '95 if that helps. Thanks for reading!

[MarkusN]

Your first problem sounds like a vacuum leak in the line going to the petcock. Such things can heal themselves, but have the nasty habit of resurfacing again later.

If you are having the problem again, try if you can remedy it by setting the petcock to "prime". If that helps, it's most certainly a vacuum leak.

[newtonent]

Get a can of fuel injector cleaner from the auto store(buy the good stuff).You can tell the good stuff by the price!Put in the recommended amount per gallon. It sounds to me like trash in the fuel. You would probably be better of to drain the tank but either way should make a noticable difference._EN

[Kerry]

The first problem you described had the exact same symptoms as running out of fuel.  If the petcock on the left side of the frame is set to ON then you will "run out of fuel" when you still have a gallon or so in the fuel tank.  This is the point at which you turn the petcock to the REServe position and start looking for a filling station.  If you run out of fuel on the REServe position, sometimes it will help to turn the petcock to the PRIme position.

Question:  Did the mechanic (or you) put fuel in the tank before you left the workshop?  If so, that would explain why it's running fine now.  (The first day I had my GS500 the same thing happened to me.  I got to learn early on about getting additional miles from the PRIme position.)

======================

As for the horrible noise, you say it only happens when the bike is warmed up?  That's kinda odd.  Can you give us a better idea about where the noise seems to be coming from?

If the noise happens at idle, maybe you could park the (running) bike in neutral.  Walk slowly around the bike and see if you can pinpoint the source of the noise.

Does the sound only happen when the bike is moving?  If you pull in the clutch and let the revs drop to idle as you go down the road, do you still hear it?  If so, it may be a mal-adjusted chain or a misaligned wheel.

If the sound only happens while the bike is revving, then it's more likely to be in the engine or clutch, or it could be as simple as two parts vibrating against each other at a particular RPM range.

Let us know!

[Ringo]

Thanks for the replies everyone!

No, the mechanic didn't put any additional gas in the tank while he was working on my bike. In fact, he barely drove the bike because he was afraid of running out of gas. He said that he drained the bike of all the gas, but didn't mention finding trash or anything there.

Anyway, what position is the petcock supposed to be in? I'm a total newbie so I don't know :/ Currently, I have it set on prime because it seemed most logical. Is it normal that the petcock can only rotate 180 degrees?

Kerry: The noise has only appeared when the bike is moving. However, I haven't tried revving the bike at standstill. I'll try the things you mentioned and see if I can make the noise appear. I'm also pretty sure the noise comes from somewhere beneath the tank.

[newbieone]

The petcock should be on "ON" only use prime for a moment or so before starting the bike.  Once you hear the bike studder while you are in motion then simply switch it to "RES" for resovir to get to the other gal or so left in the tank.  For the description of the problem you were having, it sounds like you had some trash in your tank. You may want to ask the mechanic who serviced it.

As far as the noice, I have no clue.

Good Luck

[Kerry]

Taking a longshot here, but check for loose parts like the one in the [center of the] pic below.  This part only made noise at 5,000 RPM while going down the road, but it wasn't as loud as yours seems to be.  Still, take a look...and check for loose bolts while you're at it.

I could have sworn that my noise was coming from inside the engine, and I kept waiting for the engine to seize up and quit.  Was I ever relieved when I found this!




EDIT: Changed link from sisna.com to bbburma.net.