Still Can't Figure it Out

[Stratnick]

I have posted this issue before but still cannot figure out what's wrong.
After my 2000 I/S has warmed up it sometimes idles faster than it should. It is set to idle at 800 rpm but sometimes will jump up to 1200-1500 for no apparent reason. Here's what I have done:
removed and cleaned carbs
replaced slow (35) and main jets
replaced pilot jet orings, intake orings
synced carbs
set pilot jets to 2 1/4 turns out
adjusted throttle cables

I have also played around with creating vacuum leaks to see if I can replicate the problem, but that doesn't seem to be what's wrong. I doesn't run bad when the idle speeds up, it just runs faster...then slower...etc. and ONLY after warm up or when the engine is at normal operating temp.

Has anyone else had this issue? If so, where should I be looking?

Thanks for the help.

[gordonv]

As far as I can tell, our bikes are fairly simple, not FI or O2 sensors and the like.

Do you have someone with an IS who will swap out the ICM with and see if the problems goes with it?

Maybe a link to your original post also, so we can get a little more info already mentioned.

[John Schmidt]

First, check to be sure the pilots are all set the same number of turns out, then sync the carbs. Done after you're certain there are not any vacuum leaks. 

[salty1]

I'm experiencing the same problem Stratnick. This bike sat for about 12 years, so the first order of business was to rebuild the carbs. I did not break the carbs all the way down, left them assembled in the rails. Also, did a shiny desmog, replaced the intake O-rings, all vacuum caps, etc. Checked and double checked everything, I'm fairly certain it has no vacuum leaks. It runs fine but picks up rpm to 1200 to 1500 when she warms. I have yet to sychronize the carbs. John's response gave some hope that synchronization may help our issue. Hope your post and responses to your inquiry solves our problem.

[Pete]

Have not seen this condition on a Valk
So.
I suspect one of the following three things:
Lean or rich condition when idle increases.
Lean - you seem to have tried that and that was not it.
Rich ?
Ignition getting advanced - like at cold startup.

[ValkFlyer]

A bit off the wall but since you've addressed the others....perhaps a stretch.......but If you've done the ECT timing modification, you may want to review the components for failure.

[scarylarry]

my 97 std does that...usually its after I get on it hard for awhile, after babying awhile...800 idle is @1200...not sure why...comes back down again after a day or 2

[Patrick]

This is kinda a strange one.. What does it idle at cold ?? It should be pretty low.. The throttle should be set once the engine is good and warm, but, I'm sure you know that.. Just had to say it.. For it to suddenly change like you say,, I'd suspect the throttle cable settings or there may be possibility that they are binding/hanging up..

[Blackduck]

Patrick has a good point.
Is there any slack/movement in the throttle when you move it or does  the slightest movement cause the engine to rev?
There should be enough slack so the engine does not rev when the bars are turned from side to side.
Does the throttle come back to idle easily or is it hanging up?
Indeed a tricky problem.
Has this surfaced after any work on the bike or has it always been like this?
Cheers Steve

[salty1]

Stratnick points out in his opening post that he adjusted his throttle cables. I've loosened mine to where there is a lot of slack. There has to be something else that brings about the increased rpm that we are experiencing. By the way, my, idle screw is essentially all the way out too.  When I first start it (no choke) the rpm remains low and then as it warms the rpm picks up to the 1200 to 1500.  

[Blackduck]

Idle is set with the engine at operating temperature, if you set it with a cold engine then RPM will climb when it warms up.
A question still remains, slack cables or not, does the throttle return to idle easily when released?

[Pete the Greek]

Mine did that and put in a "Dyna Jet" kit set on number 3 and it stopped , maybe a bit of luck not sure , also thru in the high performance carb springs but that took away the throttle lag when you crack the throttle ! i "Sea Form it good twice a year then run MMO every other tank or so !

[junior]

mine was doing that and i found the cure with no adjustments. i dismantaled the throttle lever and gave both cables a full dose of gunk cable and chain lube till it came out of the carb end of the cable, and lubed the carb cams(i geuss thats what they are called) and the carb linkage gets a dose every spring. that was back in 06 when i bought the bike and havent had a problem sence

[vic]

I'm having the same problem.  I changed the vacuum lines, fuel line and fuel vent hose, re-tightened all 18 band screws between the air box and carbs, new OEM petcock, and carbs synced.  When warmed up, my idle sometimes climbs to 2,000 rpm's then either goes down shortly after or at the next stoplight.  I made sure my fuel tank vent hose is not restricted and still chasing the problem.  This morning, I readjusted my throttle cable as it seemed a bit tight and I'll see if it makes a difference later on today.   

[gregc]

Sounds like the bike is doing its own coolant temp mod.   My guess would be the ICM is seeing something funny from the coolant temp sensor,  and is advancing the timming thus the faster idle. Then for what ever reason it sees the correct reading from the sensor and retards the  timming, slowing the idle down.  Follow the wires to the sensor, unplug it when the idle is high, if it slows down unpluged, I would replace the sensor.

[vic]

gregc, that makes sense.  I agree that something is causing the idle to shoot up once the bike is "heat-soaked".  Coincidentally, I replaced my temp sensor indicator unit about 2 months ago because the red overheating light was coming on.  Since I also have a Motosens coolant temp guage and it was showing the coolant temp in the normal range, I knew my temp sensor indicator unit was faulty so I replaced it.  I have a '98 Tourer so I have that setup. 

I may try disconnecting the temp sensor indicator unit like you said and see if it makes a difference.  Maybe I got a faulty new temp indicator unit.  Just like the other guys having this problem said, once the idle shoots up, there's no way to turn the idle down because the idle screw is already turned out as far as it will go.

[Stratnick]

Thanks for all the posts and ideas. I have adjusted my throttle cables and have observed them while the idle speed suddenly changes, and there is no movement that I can see. I too have suspected something going on with the cooling system as when the rad. fan comes on, the idle speed returns to normal. I will try the diagnostics with unplugging the temp sensor and see what happens.

Also, I first noticed this behavior right before I removed the carbs for cleaning and jet replacement. I assumed that the work I did on it would rectify this problem, but it didn't. Again, I appreciate the discussion and great ideas.

[salty1]

Well I figured out the idle problem on my 98 Standard. Somebody had turned out the carb synch screws too far, I have no idea what they thought they were going to accomplish.      Anyway, completed the carb synchronization and all is well now.   

[Stratnick]

Sounds like the bike is doing its own coolant temp mod.   My guess would be the ICM is seeing something funny from the coolant temp sensor,  and is advancing the timming thus the faster idle. Then for what ever reason it sees the correct reading from the sensor and retards the  timming, slowing the idle down.  Follow the wires to the sensor, unplug it when the idle is high, if it slows down unpluged, I would replace the sensor.

Using your post as a starting point, I finally ordered an engine coolant temperature sensor. I looked at the troubleshooting guide in the ignition chapter of the Factory Service Manual and it indicated that my problem could be caused by a faulty ECT sensor. Following the instructions, I unplugged the ECT and checked for continuity to the ECM and all was good there. After installing the new ECT sensor and refilling the rad. with new coolant, the bike runs very differently. I rode a few miles down the road and it has noticeably more power, and idles correctly so far. When the rain is over, I plan to ride it for 20 miles or so to really test it out. Your theory about the timing be affected by a faulty ECT sensor was helpful. I would have never figured it out. Thanks!
 I will post again after a good, long test ride.

[Bill anderson]

I don't know if this will help or not but I had an 83 wing with the same problem.
The carb slides had a teflon coating on them that wore away causing the slides to hang up when warm.Honda did a recall on them and replaced all slides.
Might be worth taking a look at them for any scoring.