Irratic idle

[davelength]

I have a 97 GS500E that is having some weird idle problems. The idle was somewhat irratic and was dieing occasionally at stops. I pulled the carbs and went through them, though I did not see any obvious problems or obstructions. I gave them a good cleaning and set the fuel/air mixture screws at 3.0 on reassembly. I also replaced the spark plugs a well, though they looked normal.

This morning the idle seemed stable at first, though once the bike really warmed up, the idle kept wanting to stay or drift up around the 3k mark. I could drag the clutch momentarily while at a light to bring the rpms down, and once it was around or below 1k, the idle would stay there and act normally.

I might have the carbs set a little rich so I will try playing with that, but does anyone else have any ideas? The curb idle adjustment does not seem to have any affect until you have turned it a good full turn or so, at which point it has a drastic affect. I have it where it seems to be the best balance between too low and too high.

Off-idle the bike runs great. Maybe the bike just does not like to sit still..?   Anyway, if anyone has any thoughts or suggestions, that would be great.

Thanks!
Dave

[scratch]

Do the carbs have the stock jets? The jetting is lean for Cali, and that may be why your idle is hanging around 3 grand. Change your pilot jets to size 40 non-bleeder type jets and that will hopefully fix it. Do a search for the exact part number.

[octane]

I was having a similar problem and after months of frustration found a hairline crack on the underside of one of the carb boots that was causing a vacuum leak. While you're at it, make sure the vacuum caps on the carb tops are snug (and there!!).

[davelength]

Thanks guys.

octane, what do you mean when you say "carb boots?" I did not notice any cracked hoses or anything, though I may try the flammable spray test to see if I can find a vacuum leak.

scratch, I'll look into the larger jets as well, since it sounds like a fun mod anyway

Thanks again!
Dave

[Kerry]

octane, what do you mean when you say "carb boots?" I did not notice any cracked hoses or anything, though I may try the flammable spray test to see if I can find a vacuum leak.

I think you're both on the same wavelength.

[davelength]

I did not find any vacuum leaks yet, though I am definitely still looking. I am going to go by a friend's shop after work and sync the carbs. If they are really off then that could be the problem itself, or at least tell me more about what is happening. I'll let you guys know what happens.

Thanks!
Dave

[mtbman]

Hey, I have been having the exact same problem on my 92.  I replaced the two tiny O-rings for the vac. ports on the top cover of the carb.  That made a huge change and my engine no longer "sticks" at 3K.  The resonse is still slow so I am going to try to find more leaks.  Please post if find any solutions though, I would love to hear them.

[Daniely]

Just a though, since im still not that familiar with bikes. Is there any chance it could be a problem with the choke?

[davelength]

Ok, I synced the carbs which were slightly off, but that was not the issue. I also tried looking again for a vacuum leak using both propane as well as wd-40 and did not find anything. At this point I am thinking it needs a valve adjustment. While I had the carbs off I did notice that one intake valve was much cleaner than the other, which would suggest that the dirty one is a bit tight.

Does anyone know if this has mechanically adjustable valves or is it the shim-over-bucket style?

Thanks!
Dave

[mtbman]

They are the shim style, I was really hoping that would be my problem, but my valves were spot on.  Hopefully it will work for you.

[davelength]

Well I finally got around to adjusting the valves and it solved the problem. It is like a completely different bike now. Easy startup, smooth idle, good power.  Both exhaust and one intake were tight, the other intake was loose. One of the exhaust valves was so tight that I went down 3 shim sizes (.15 mm) and was still on the tight side of the range.

I highly recommend anyone to check/adjust the valves if they have not done so in a while.

Thanks!
Dave

[mp183]

I had a problem that turned out to be the valves.  The idle would shoot up in traffic to 3,000 rpm.  I would adjust it down.  Next time I started it, the idle would be too low.  As it got worse, it would start off almost on one cylinder for the first 10 seconds.  Had to slip the clutch to takeoff.

Ok, I synced the carbs which were slightly off, but that was not the issue. I also tried looking again for a vacuum leak using both propane as well as wd-40 and did not find anything. At this point I am thinking it needs a valve adjustment. While I had the carbs off I did notice that one intake valve was much cleaner than the other, which would suggest that the dirty one is a bit tight.

Does anyone know if this has mechanically adjustable valves or is it the shim-over-bucket style?

Thanks!
Dave