Intermittent high idle

Hello,
I have a '96 VFR750 w/15k miles that has an idle issue that I have not been able to figure out ???. It has done it intermittently for as long as I've owned the bike (I bought it with about 5k on the clock)

I had it do it today when I went to start it, here's what it does (always on a cold start)

I turn on the key, set choke to full (60 deg F outside temp) give a twist or two to the throttle (carburetted engine) and then hit the starter. After a few hits, it fires and sets up an idle around 800 RPM (a little slow)

I let it run for a few moments and the idle picks up to a normal 15-1600. I'll take the choke off as soon as the idle sounds good and it'll let me blip the throttle without bogging down on RPMs.

Now here's the frustrating part :-[ Instead of the idle going down, it will slowly pick up until it is sitting right at 3000. Choke is full off, there seems to be no kinks or abnormalities in the cables, but it will not come off of that high idle. It will usually come down again eventually, but it's embarrassing to be sitting there with an engine revved that high.

It doesn't do it every time and it only does it on cold starts. turning it off and restarting it will not bypass the problem though.

Has anyone else had or heard of this problem?

Sorry about the long question, but I wanted you to know as much as possible about it. Thanks... B

 

Looks like I'm the only one who's had this problem.

I'm curious if it might be that the choke is sticking on, even though I am returning the choke lever to the off position. Is there a good way to check this without tearing into the bike? B

 

Hi Brian,

Sorry no one could help you out with this problem.  Try posting the same question to the Honda VFR Club forum in the UK.  They have a lot more interaction with that site.  Here's the link...  http://www.hondavfrclub.org/forum/index.php?s=

 

I have a similar problem. My bike will start up, choke works properly, and the idle will hang around 3-4k after i have been riding it a bit. It doesn't matter how hot it is out. I've tried lubing the throttle cables, just cleaned the carbs and set the idle. Any help appreciated.

 

I picked up my 85 VFR a few months ago, and it just got cold here in Texas during thanksgiving. I rode the bike again yesterday and today, and I have exactly the same problem. The idle starts pretty normal, between 1000 and 1500, then gradually picks up to 3000 and stays there. It didnt do this when I bought it, it just started yesterday. The only change that had happened since the last time i rode it (less than 1 week before) was cold weather.
Has anyone figured out how to fix this problem?

 

As was said before, sticking choke plungers/cable. If you can put the choke plungers in at all, either the cable is too tight or the plungers need cleaning.

Maybe an air leak around the carb boots?

Carbs out of sync?

 

When I move the high idle lever back and forth, there is almost no resistance from choke to about 2/3 of the way to fully open. Also, there is no change in RPM or engine noise. If I move the lever farther than 2/3 of the way, it revs higher. Once the bike warms up, it stays constant at 3000 RPM.

Im pretty sure it is a stuck cable, but how do I unstick it?

 

it's positively amazing the number of riders who don't know to use the hand adjusted "idle speed adjustment" screw down on the side............that's why it's there!! so find it and use it...

most cases where bike idle just suddenly jumps up are caused by one cylinder that's "sleepy" and doesn't wake up until some heat gets going.......probably clogged jet or using too much choke and flooding plug.......

i appologize for the too big photo!!

 

Thanks for the sarcasm squirrelman, but i will repeat once more, this has NOTHING to do with the idle control screw. The problem is most likely in the choke cable, or possibly whatever the choke cable is attached to. I would appreciate some useful guidance on how to check/fix the choke cable, but I do not need any more responses about the idle control screw. I am trying to appropriately fix the problem. What you are suggesting is comparable to people that duct tape on their front bumper.

My choke lever has no resistance in the lower 2/3 of its range, this means that the cable (or whatever it is attached to in the carbs) is stuck 2/3 of the way open. This is why after warming up, the engine idles at 3k RPM. If i adjusted the idle screw, I would still only have use of 1/3 of the choke lever, and I probably would not be able to adjust the idle screw enough to mask the real problem.

Has anyone with an older VFR (no auto-choke), or even any other carbed bike, had a similar problem? I could probably take stuff apart and figure it out on my own , but I do not want to risk getting in over my head and not knowing how to fix it, or worse mess it up more. Any help on unsticking a choke cable / carb thing that the cable is attached to would be great, but please no more idle screw suggestions. I know where the idle screw is, and it is not the problem.

 

Sorry.....
you need to remove fuel tank, remove both top and bottom of airbox to see where choke cable goes and watch the action as you move it through its range of motion. no way will the carbs need removing...
this is simple stuff, don't worry.

ALSO get ahold of a cable lubrication device and spray-lube the choke cable because it sounds like your cable is dirty/corroded and not returning to full OFF position.

BUT, as others have mentioned, you may have an air leak around the carb mounts, so remove side fairings and use long phillips head screwdriver to check tightness of all 8 band clamps securing rubber carb mount sleeves......


GOOD LUCK>

 

Thanks Squirrelman!

 

My choke acts similar to yours. No real tension in the lever until 2/3 through the total travel. The no resistance is likely the slack in the cable. The choke and throttle cables are extremely sensitive to any tension on the cables.

I had to have my choke cable that loose to ensure that it did not move when the handlebars moved from lock-to-lock. I plan to re-route the cable this winter.

That being said, when the choke is fully open, my bike idles around 3,000 like it is supposed to.

Try bypassing the cable altogether. Remove the choke cable from the linkage.
- Manually raise the choke plungers by moving the linkage. Visually ensure all 4 lift.
- Let the linkage back down "slowly".
- If you can still push in any of the choke plungers AT ALL, the plungers are gunked up and need cleaning or the linkage is catching.

If all 4 choke plungers are OK, then reattach the cable and try the same procedure again.

If, after this and the same issues still appear, get a carb sync done. A badly adjusted carb(s) can pull the others up to the high rpm you're getting.

- Also check the throttle linkage to insure nothing is stuck there preventing the throttle plates from closing.
- When you let go of the throttle, does the grip return to it's stop quickly? You should hear the throttle plates SNAP shut. If you don't hear the SNAP, the throttle cable is preventing the plates from closing all the way - causing the throttle to be partly open all the time.

Another thought, when the bike is warmed up and idling at 3K, does moving the choke do anything. It should cause the idle to lower from the over-rich condition. If nothing happens, then your chokes aren't closing like they are supposed to.

 

the adjustment for the choke cable is the threaded sleeve with locknut that screws into switch gear. if you wanted, you could screw OUT that sleeve and get choke action earlier in lever travel without lost motion..
also, to lube cable just unscrew the 2 screws on left switches, leave bottom alone and gently move top half up and foreward to expose choke cable and keep spraying cable hole with your favorite lube..

Mason's info above is GOOD!

 

thanks mason and squirrelman.
I have moved the fuel tank and air boxes, and the lever that the choke cable is attached to can be pushed closed all the way, but it will not do it with the choke alone.
I took apart the left controls, and the choke cable is partially frayed right where it connects to the choke switch, also there are 2 pretty significant kinks in it. WD40 helped slightly, but it still does not have full range of motion, I think I need a new choke cable.
Does anyone know where I could find one? or even exactly what the part number is for a choke cable on a 1985 VF1000R?

 

So... I straightened out the kinks with some pliers, and loaded the cable up with WD40, and it is fixed for now.
The cable is still halfway frayed, so I am going to replace it as soon as I get the new one. Woods Fun Center had to special order it, I should get it in a week.

Does anyone think I should take pictures of the process and write up a well illustrated how-to?
It is a pretty simple process, but I am doing the work anyway, so if theres any other bike mechanic rookies out there like me, it would be a nice guide.

And on that note, how do I go about posting pictures into a thread, do I need to upload the pictures online somewhere first? If so, is there a good free image host that anyone wants to recommend?

And thanks again for the advice mason and squirrelman

 

Tip when replacing cables or hoses.

Tie a string to one end of the old cable. Remove cable and untie the string. Now tie the appropriate end of the new cable to the string and pull the other end of the string. The string will pull the cable through, using the same route as the old cable.

Saves alot of time and aggravation trying to "push" a cable/hose.

 

Hey everyone, thanks for the great content above! I am also now experiencing the High idle issue (2K-3K) after warmup. I was wondering if anyone found the resolution to this issue or what maintenance was required to fix the issue.

Thanks!

 

"now"

Everything has been perfect and all of a sudden?

Give us some history please.

Has it sat unused?
Is this bike new to you?
Miles on the bike?

I'm assuming from your profile pic it is a 1994 - 1997 VFR.

 

Thanks for the response "Captain 80s"

- The bike is a 1996 VFR 750
- The bike is new to me, two previous owners, currently has 26K on the odometer.
- Previous owner said the bike had sat for some time unridden. I rode it a hundred miles or so before experiencing the issue.
- I have inspected the carb plungers and lubricated the linkage. All plungers seem to be extracting and plunging with zero free play or looseness.
- Idle adjustment is set to the appropriate position.

Technically the issue started after I changed the oil/filter (of which I am very comfortable doing), but I don't see how that could cause this issue.

I've reached a point where I have no experience of pulling the carbs, and am a little hesitant to get in there. My next move is to inspect the carb boots for any potential cracks or damage, but this of course means removing the carbs. After that I would assume a carb sync would be in order if there is no damage to the boots.