View Full Version : increasing idle at neutral

03-13-2007, 08:27 PM
Well I sync'd the carbs today and have not rode that far to see if it is still doing it but here is what my issue is. When I am riding and the engine is heated up I might come to a light I stop and squeeze in the clutch and the idle does not drop to 500-900 or where ever the idle is set, it just stays up at 2500 ish. I release the clutch just to the point where the clutch grabs. It then idles down and stays at 500 - 900. What do you think? F/A settings or will the sync take care of it?

03-13-2007, 09:24 PM
Adjust the idle. I had to do the same thing after a carb sync. I'm not sure where your idle adjustment is, I have an 06

The CyberPoet
03-13-2007, 09:57 PM
Probably the throttle cable is too tight or routed wrong, plus sticking linkages between the carbs.

=-= The CyberPoet

03-17-2007, 12:55 PM
Let me re phrase this. When I am riding and the engine heats up and no choke is applied...I will get to a traffic light or come to a stop the engine that normally idles down at 700ish which the idle is set at will not drop down to idle. It will remain up at 2000-2300 and not kick down unless the clutch is released slightly till it grabs and slows the engine down. Then it will idle at 700ish. It is not a bound cable or a linkage problem, it is not persistant. It is semi frequent.

03-17-2007, 04:40 PM
600 i think is to low of rpm, i think it is suppose to be around 1100 +-100 rpm.

03-17-2007, 06:58 PM
If I'm reading it correctly, this sounds like a "hanging idle" issue...

He probably has the idle set so low to limit the number of times it hangs at 2,500rpm since, if the idle were set to 1,100rpm, it would hang (on decel) a lot more often.

And, when the idle does hang, the only way to get it to come down is to slightly load the engine with the clutch. Does this sound right, MXG?

03-17-2007, 09:43 PM
Hey MXG, I have the same bike(96 600f) and I also have the same issue. When I first got the bike(recently) I cleaned the carbs and then started her up, let her run for awhile, and then set the idle to around 1100. However, after i rode it a bit and got to operating temperature it would idle too low and die at a stop sign. So I readjusted the idle to where it would stay at about the 1100 mark, and it does this now when I start it, but now I also have the same issue where it will idle around 2500 when i'm at stops with the clutch in. Maybe I should just try readjusting the idle but, The repair manual does call for an idle of about 1200, and to be set after the bike is at operating temperature. I'd rather have it idle high than die on me though.

03-17-2007, 09:46 PM
....i rode it a bit and got to operating temperature it would idle too low and die at a stop sign. So I readjusted the idle to where it would stay at about the 1100 mark...

It is best to ride the bike for awhile, let it get up to operating temps and then adjust it, then in general that setting should be best all around.

also seeing the age of your bikes I would probably guess that you have some form of rust in the fuel tank. That could cause alot of problems. I would suggest using por-15 tank sealer. THere is a write up just recent on the forum to show you how to. I also have a pre98 and regretfully have to do it as well, but if it is what it takes to get my bike right, so be it.

So i would suggest coat the tank, and while the tank is curing tear the carbs apart, remember to keep parts together i.e. parts from carb 1 should go back in carb 1. Take pictures for reference. Find all worn parts. Emulsion tubes (the brass tubes that the mains screw into and the needles drop into) and needles are like places to find worn. Also o-rings are a big place that causing problems. So order all your parts, will be pricey new emulsion tubes are ~$20 bucks each. Most people suggest sourcing a second set of carbs off ebay. **There is alot of pre98 carbs on ebay right now.

Needle valves are a place that wears very common. One from early 90's gsxr works(well atleast for the 750's). The needle valves are in the floats that stop fuel flow. Also o-rings on the floats are cause for problem.

Ok, so put all your carbs back together and bench sync them. Put the carbs back on the bike, attach cables(freshly lubed up and check condition, and route appropriately). Put the tank back on with new fuel filters in the fuel lines. And put in new gas and then sync up the carbs.

There are most likely other steps in there and some others have some good ideas on what to do, Like compression check, check resistance on coils, new plugs, etc all that other stuff.

Starting over and doing everything right will be the best in the long run. It will also stop the need for finding bandaide fixes down the road that covers up one problem just to later make it all go to hell in the end.

03-17-2007, 10:55 PM
I'd agree with Cyberpoet, that was the problem on my bike.

Check the throttle cable.

03-17-2007, 11:22 PM
try the fule mix screws sounds like it is to rich

03-18-2007, 09:38 AM
....i rode it a bit and got to operating temperature it would idle too low and die at a stop sign. So I readjusted the idle to where it would stay at about the 1100 mark...

...I would suggest using por-15 tank sealer. THere is a write up just recent on the forum to show you how to....
... tear the carbs apart...
...So order all your parts, will be pricey new...
...Put the tank back on with new fuel filters in the fuel lines....
...Starting over and doing everything right will be the best in the long run. It will also stop the need for finding bandaide fixes down the road that covers up one problem just to later make it all go to hell in the end.

Thanks for the advice. I have already coated my tank with por15 and if you look at that how-to post again you'll see that I had put my ideas and input about it in a reply. However, I did not put in-line fuel filters on, because: 1, I didn't feel I needed them since my tank is now wonderfully coated, and 2, I just put a new petcock and regular fuel filter on, and heard that those fuel filters are pretty good, and plenty for a coated tank. Besides, I'd have to buy two in-line filters and that's just too much trouble for what I don't think would be much benefit. Would it really be worth it?
As for tearing the carbs apart, I did a couple weeks ago to clean them, and now they're apart in my garage again, since i need to do float adjustment. Every cent I spend on the bike my wife gets more angry, so I won't just buy new parts until I have to. So yes, I'm dealing with the back to hell from band-aide fixes. I am happy that before a few weeks ago I didn't know anything about a motorcycle and now I can take the bike apart down to the carbs. So taking it apart over and over again is sort of enjoyable.

03-18-2007, 11:32 AM
Man, I miss two days and everyone is answering me. I just had the carbs rebuilt by a local shop. And they set the Idle hang was kinda weird and they were not sure of what was causing it. Loading the engine with the clutch does help. All the cables are new and routed the same as before. The tank looks pretty good like someone must have taken car of the bike "no rust" I have a feeling its a setting. Might be too rich might be too lean might just need to be tuned I dunno. The idle is kinda touchy there is a fine like between idleing low and idleing way high. I will be upping the idle when the bike hits the road again though.

03-18-2007, 12:01 PM
nathan-yeah i read the how to but didn't read any further. I have been putting off the tank coating and just gotta do it.

as far as the inline fuel filters, i couldn't tell you which substrate filters better or whatever, but i know the petcock just has a screen and things still can get through. But look at a car, they have filters in the tank and also an inline filter. so i would just assume it would be a good thing. just cheap insurance. Yeah buying two filters would be a pain in the ass, expecially the line that goes between the first two, but with it i didn't cut the line and put it in midway, i put the filter on the end and put 4 inches of line on the other end.

yeah i am still doing the bandaide fixes as well, I couldn't find any shop that would even touch my bike, but finally found one. I don't know as much about motorcycles as a car and the motorcycle is so more here and there so sometimes i just get to mad and start all over from square one. I just tell myself, and might be a good argueing point, but I just say when i have to buy something is that, why even have the thing if it is broken and I can't sell it because i would not get half the money out of it. And the point of not being left on some back WV country road.

mxg-I think a true hanging idle problem would be a lean condition. Where you rev the bike and as the needle is sweeping down it will stop at about 2k for a second or two and then fall to the idle(1100 rpm), that is always how i took a hanging idle. If it doesn't fall and stays at 2k, there is problems else where. maybe try and get some techron and put in the tank and run a tank of it and see if it cleans it up, maybe that will help. -- that is where i am. oh and if you can maybe do a sync again.

03-18-2007, 12:15 PM
sync'd and techroned. still there. no bs Ive done that already. I still think its a setting.

03-18-2007, 12:27 PM
dang, i just got the sync left. i just did the techron. i hope that helps, but if not back to it.

03-18-2007, 01:35 PM
,,, next time that it happens rather than engaging gears at over 2500 rpms and getting that unsettling "CLUNK",,, switch the engine off button (big red button) to off and on VERY, VERY rapidly,,, as in one single motion, don't worry, if you do it very fast it won't turn the engine off and the bike will idle normal again.

This will not fix the problem per se but will fix it for that one particular stop, it sure beats the other options at least until you find the source.

Mine's been doing that for a long time and I got the technique down to an art... it only happens as you described when the engine is fully warmed up, especially on hot weather riding.

Good luck and post if ya ever find the cause.

03-18-2007, 01:41 PM
i'll see if that works is it as well 2000kat600.

03-18-2007, 04:57 PM
yeah... I just took the carbs apart and recleaned them and adjusted the floats, which fixed my previous problem, however, I still have the same deal with the idle either too high or too low once the bike has been running hot.
Maybe we should all buy Ivan's carb kits they were trying to get him to make.

03-18-2007, 07:53 PM
Well i spent awhile longer riding and adjusting the idle.
I finally got it to idle at 2k for medium hot, and 1k after a long ride. So i think that's how it's going to stay.
Getting it to that point were it ran well was a lot of adjusting, but I think if you just keep doing it, you can get it right, if that's all it is.

03-18-2007, 08:22 PM
if you don't mind post up your settings to help out mx or anyone else having the same or similar problem

03-18-2007, 09:17 PM
I don't really know what you mean by settings.
I just simply turned the idle adjuster screw back and forth 'till it ran best. If you mean the pilot screws in the carbs, they're all about 2 and a half turns out. I haven't even synch'd but it looked fine as far as the valve openings and since it's running smooth I wasn't worried about that.

03-18-2007, 09:56 PM
settings as in number of turns out on the pilot screw, brand of jet kit if applicable, K&n pods or k&n stock replacement with airbox or stock filter and stock airbox, what needle position, main jet used, float height.

03-18-2007, 10:17 PM
Everything is stock except for exaust which is yosh. Like i said, the pilot screws are 2 and 1/2 out. Float height is as suggested in repair manual at .57 inches from top of gasket to top of float. The floats took a little bit for me to figure how to bend them right. You just have to lift the float a little bit then push the little metal tab down so it rests sooner on the pin. then the float is higher, or i guess pull it up if yours are too high. mine were all too low though.