Jump to content
Sign in to follow this  

gets hot and idle hangs?!

Recommended Posts

If I ride my bike hard for a while (1-2 hours) the idle starts to hang when I give it some throttle before it drops off. It can be very annoying. it is like the throttle sticks but I dont think it is from the carb or throttle because I keep them very clean and once I let the bike cool down it goes away. any suggestions??

Share this post


Link to post
Share on other sites

Mine did it both before and after the grey wire mod.

I've read that part of the problem can be in the decel enrichment circuit.

Pilot jet or a tight throttle cable are a couple of other potential causes.

Share this post


Link to post
Share on other sites

Usually a hanging idle is a result of being lean on the pilot circuit. If you don't have any air leaks in the intake tract or exhaust, open your fuel screw in 1/4 turn increments until the problem disappears. If you end up more than 3 turns open from fully seated, then go up one size on your pilot jet, start the fuel screw a 1/2 turn open, and begin adjusting again until it quits.

If there are no air leaks present, usually a tweak on the fuel screw takes care of the problem.

I've never heard or experienced the idle hanging because of the gray wire mod. The grey wire mod changes the WR ignition timing above 7000 RPM to YZ specs. I can't see how that would affect anything at idle, but maybe in some cases it can have an effect. If so, the problem is easily corrected with a little adjustment to the fuel screw.

Share this post


Link to post
Share on other sites

ditto on the pilot jet. After I installed a #45 pilot jet I set my fuel screw ~1 1/4 to 1 1/2, depending on weather, and my idle hang is gone. It will also help if you can verify that you idle is not set to high. If you don't already have a tach you should get one and so you can set your idle according to the manual.

Share this post


Link to post
Share on other sites

Something that hasn't been mentioned yet as a cause of a hanging, unstable idle is tight intake valves. That's exactly what happened to mine. Check your clearances.

Share this post


Link to post
Share on other sites

Interesting. Checked my buddy's yesterday... .10, .07, .10

All three had 192 factory shims, about 350 miles.

We're going to change all of the shims to 190, 185, 190.

Exhausts were fine at .19

I'd have to say though, that my "hanging idle" has actually improved in the 350 miles.. it'll be interesting to check my clearances.

Share this post


Link to post
Share on other sites

On the bottom of the carburetor bowl towards the front of the carb is a recessed hole. Up inside that hole is the fuel screw. Many people install an after market fuel screw like the Zip-Ty to make adjustment easier. Costs ~$20.

Share this post


Link to post
Share on other sites
Did you or a previous owner remove the grey wire. That will cause your idle to hang.

I have done the grey wire mod on my bike and 7 or 8 of my buddies bikes (they were chicken to do the free mods). I have never had it make the iddle hang on any of them. I would look at you jetting. :)

Share this post


Link to post
Share on other sites

My idle was hanging and I took it to the dealership and they told me the fuel accelerator was bent. Whatever they did, it fixed the problem.

Share this post


Link to post
Share on other sites
Something that hasn't been mentioned yet as a cause of a hanging, unstable idle is tight intake valves. That's exactly what happened to mine. Check your clearances.

Now you starting to scare me :):p:D:)

Share this post


Link to post
Share on other sites
Interesting. Checked my buddy's yesterday... .10, .07, .10

All three had 192 factory shims, about 350 miles.

We're going to change all of the shims to 190, 185, 190.

Exhausts were fine at .19

I'd have to say though, that my "hanging idle" has actually improved in the 350 miles.. it'll be interesting to check my clearances.

To cause problems at idle, the intakes have to be so tight that they are actually held off the seat when hot, which will disturb the intake air flow and cause the mixture to fluctuate. Your measurement of .07mm is probably not tight enough to cause that. When mine started acting this way, I found 2 of them at or actually less than zero.

Share this post


Link to post
Share on other sites
Your measurement of .07mm is probably not tight enough to cause that. When mine started acting this way, I found 2 of them at or actually less than zero.

Ya... I didn't think 07 was too bad. So, when the engine heats up, the Al head expands more than the steel cams and Ti stems, so tolerances will actually open up once warm.... right?

So... even though the 07 is out of spec, is it enough to worry about and reshim now, or should we wait until all three of them tighten up?

Share this post


Link to post
Share on other sites

buy the size smaller shims now, but wait until it gets cranky to start.

The tighter the clearance, the higher the lift, the higher the hp. When you reshim it's the same as putting a milder cam in the bike.

Share this post


Link to post
Share on other sites
Ya... I didn't think 07 was too bad. So, when the engine heats up, the Al head expands more than the steel cams and Ti stems, so tolerances will actually open up once warm.... right?

So... even though the 07 is out of spec, is it enough to worry about and reshim now, or should we wait until all three of them tighten up?

Based on the way they behave, I'd say the clearances either stay the same or close when warm (note that the exhaust has more cold clearance). When mine started the hanging idle thing, it had compression while cranking when cold, but seemed not to when hot.

On whether to shim, I think I would do it, because it is out of spec. OTOH, it's only out by .001" or so, so it isn't going to be a killer if you don't, and if it was the difference between riding or waiting for parts, I'd ride it. But, if you've never had it apart, you don't know what shims to buy, so while you're discovering that, you can shim the one valve, and have what you need for the other two when they actually need to be done.

Share this post


Link to post
Share on other sites
But, if you've never had it apart, you don't know what shims to buy, so while you're discovering that, you can shim the one valve, and have what you need for the other two when they actually need to be done.

We tore it down completely to check. Stock shims are 192 on all three valves. By the book, we'd just need a 185 to bring the .07 to a .14, but since we're in there and the two outside are at the minimum .10, we're thinking of just buying the straight 190 and bringing those two up to .12

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×