me again... 2007 GS500f high idle when reaching operating temperature

[Gcook57]

I am really getting frustrated trying to fix this problem my 2007 GS500 starts good idles at about 1750 but after I ride it for about 5 minutes and it warms up the idle all the sudden goes up to about 3500 RPM I've tried everything suggested making sure the choke linkage isn't binding adjusting the choke cable everything checks out okay as far as that I pulled the carbs blew  the Jets Out the throttle and return cable are both operating properly and adjusted right the only thing I haven't done is adjust the valve but the bike only has 4200 miles on it I really don't know anything else to do other than that it runs like a screaming banshee

[Jim Moore]

You're on the right track, but you're trying to fix the wrong side of the problem. You want to have a good idle after the bike is completely warmed up, not when it first starts. (That's what the choke is for.) So, start it and ride for a good ten minutes. These bikes take forever to warm up completely. Don't start making adjustments until the bike is completely warmed up. Once the bike is completely warm you can adjust your idle with the big idle screw. You can see the idle screw in the first pic of this thread.

http://gstwins.com/gsboard/index.php?topic=56601.0

You may encounter another problem as you work your way through this, the dreaded hanging idle. You may find that as you roll of the throttle the idle rpm will hang up before slowly returning to idle. This is caused by a lean condition. You fix it by turning the idle mixture screws out (4th pic in the thread above). You can reach in and turn them with the carbs on the bike with a tiny screwdriver. Every time you do that you will need to readjust your idle with the big screw. It just becomes a matter of playing with everything until it's right. Note that if you get to about 4 turns out with the mixture screws you need to go to the next bigger pilot jet. You don't want to go past about four turns.

[mr72]

Exactly what he said.

Although I'd start with setting the idle using the mixture screws rather than the "big" idle speed screw (which really is a throttle butterfly stop), and then only use the big screw to fine tune the idle speed once the mixture is bang-on. So use the big idle screw to make sure the bike idles without stalling, or to set the idle to like 2K rpms while you adjust the idle mixture, then back it down so the bike will idle at 1200 rpm. And after you ride it for a month, you will wind up tweaking that big screw 1/8 turn at a time while you are on the bike at stop lights until it's perfect.

[ajensen]

Tight valves can cause idle problems.

[motenz2]

I'm having what sounds like an identical issue as you.  Bike starts easy, but once it's warm and riding the rpm's stay high (around 3,500 rpm). Although with my '05, the rev's slowly come back down to 1,200.  It'll idle all day 1,200.  I also noted that both of my spark plugs indicate the bike is running very lean.

How do your plugs look?  Have you troubleshot anything else? 

In line with previous suggestions in this thread, I fine-tuned the mixture screw - experimenting with settings from .5 turns out all the way to 4 turns out.  Oddly, the bike ran worse when I went to 3-turns out and beyond -- this was counter intuitive -- more turns out should have made the bike's mixture richer but instead it was acting like it was even leaner.

I extensively searched for an air leak and I haven't found any.  I'm suspecting I have a bad vacuum control valve (the solenoid under the right side carb) which opens the vacuum valves on top of the carbs/slides.  I unplugged one of the vacuum lines and found there was no vacuum/suction.  Also, when I unplug the electrical connector, it made no difference in how the bike was running.

Very frustrated -- I'm half tempted to go to a GS500E carb vs. the F.

Steve

[ajensen]

Adjust valves, clean carbs, and remove or plug all the extra vacuum lines. After I did those things, my 2006 500f runs quite well.

[RideShield]

After recently replacing my spark plugs I followed Mr72's quick instructions for idle adjustment located on the second page of this discussion:

http://gstwins.com/gsboard/index.php?topic=71601.0

My 2007 gs500f doesn't appear to be running worse so I'm taking another ride today to try to fine tune it again. I should mention that when I replaced my left spark plug the bike was running better, not sure why 

[motenz2]

ajensen - can misadjusted valves account for the very lean condition?  Or are you suggesting I may have multiple compounding issues?

Thanks for the input.  I'm going to pop the head cover and check the clearance while I have the tank off already.

Steve

[ajensen]

There has been a debate about if and how tight valves affect idle. My theory is that if the valves are too tight, the engine does not run well until it gets hot. Then, because the valves loosen up when the engine is hot, the engine starts running more efficiently--thus the high idle. If tight valves are the problem or are contributing to the problem, and you set the valves looser (see other threads), the engine will run high when it is cold. Then, you can back off on the idle screw (the big white one between the carbs). I hope this makes sense.

[motenz2]

It does make sense ... I'll report back on my valve clearances once I measure them ... hopefully this weekend.  In parallel, I'm still chasing/troubleshooting my lean condition.

[mr72]

On the contrary tight valves result in no compression when hot. Bike will run better cold and might not run at all when hot if the valves are sufficiently tight.

Your problem is not valves IMHO. Not a bad idea check anyway but I think you are barking up the wrong tree

[ajensen]

Are you sure that GS500 valves tighten up when hot? If so, it is the only engine i know of that does so.

[Jim Moore]

Are you sure that GS500 valves tighten up when hot? If so, it is the only engine i know of that does so.

That's the whole theory behind valve adjustments. You adjust the valves to have a slight gap when cold. When the bike warms up the valve stems become longer, closing the gap. If your valves are tight when they're cold then the valves can actually be held open slightly when the engine warms up.

All engines with mechanical lifters behave in that manner.

[gsJack]

Valve clearances increase as the engine warms when you have an aluminum engine.  The coefficient of linear expansion is greater for aluminum than for steel causing the cylinder head height to increase faster than the steel valves length lifting the camshaft away from the valves.

[mr72]

TO THE OP: the problem you describe is simple. The idle is set too high, nothing more.

Here's how you should be starting and running it, and how it should behave:
1. start the bike with choke on. It will start and within a few seconds the idle will climb to 5K rpm or so. This is "fast warm-up" mode. Note, the choke is not actually a choke, it's a jet that gets turned on to enable this fast warm up. Let the bike run like this for 30-60 seconds or so while you get ready to ride (gloves, helmet, etc.)
2. Begin to ride with the choke on (fast warm up). Turn the choke down to 1/2 or so once you get rolling, keeping enough choke to prevent the bike from dying when you stop and idle, but not so much as to keep the idle at 5K rpm. After a minute or two you can probably turn the choke all the way off.
3. When the bike is still cold (less than 15 minutes of ACTUAL RIDING) the idle will likely be low, around 1000 rpm or so. The idle speed will eventually climb to 1200 once the bike is FULLY WARMED UP, which really does take 10-15 minutes or more of actual on-the-road riding, much longer if sitting on the center stand idling.

The moral of the story is, for the first 10-15 minutes of riding you may have to "nurse" the throttle or leave a little bit of choke on to keep the bike from stalling at stop lights if the idle speed is set correctly or at the low end of normal. If you are primarily riding short trips and don't get the bike fully warmed up then you might benefit from setting the hot idle more like 1400 rpm so it is more stable when it's cold.

Anyway, like I said, your problem most likely is not valves. Adjust the idle correctly WITH THE BIKE FULLY WARMED UP and the problem will go away, if not completely, at least enough to reveal whatever other problems you may have.

If you attempt to set the idle correctly (speed and mixture) when it's hot and it turns out you can't adjust it so that it will run under 1500 rpm, that is the bike simply won't idle at under 1500 rpm or so when hot (dies/stalls), then you probably have tight valves or a vacuum leak (or, more likely, both). You should check the valve clearances to level set and fix them if they are out of spec (too small), since it will impact whether you can eventually get it to idle correctly. While you have the tank off doing the valve clearance check, do yourself a favor and replace the intake boot o-rings since they are likely shot and it will eliminate one of the most common causes of vacuum leaks.

[sledge]

Valve clearances exist as much as anything to compensate for the tolerances involved in the manufacture of various parts.

Max seat depth from head face
Overall valve length
Camshaft center to head face
Camshaft concentricity and run out.
Bucket thicknesses
Camshaft bearing clearance and wobble.
Actual shim thicknesses (and their own barn door tolerances!!)
Lobe heights from camshaft center

If you took the figures in mm to three decimal places of those key measurements there wouldn't be two engines in existence that would share them across the board.

Valve clearances (and their own tolerances) compensate for these differences.

Imagine building a 100ft brick wall starting from each end and expecting the middle brick to fit perfectly........its just not going to happen 

[Gcook57]

 I followed your procedure the bike started right up on choke it idle high and I drove it for a little while until it came to full operating temperature then I adjusted the ideal to about 1300 RPM I drove it about 40 miles it rad Drake has tons of power but I'm noticing that it takes a little bit of time when I let off the throttle for it to go back down to a good Idol during a 40-mile ride four or five times when I came to a stop the idle State at about 3000 when I was stopped at a light in first gear idling at 3000 I let the clutch out a little bit to put a load on the engine and drop the RPM and immediately pull the clutch back in  after I do that the idle drops back down to normal what would cause this sporadic problem

[Jim Moore]

That's a lean condition causing the hanging idle. Get everything warmed up again. Turn your mixture screws out a quarter-turn at a time and re-test until it goes away.