Idle keeps mysteriously lowering while riding - Honda Motorcycles - FireBlades.org
Honda CBR 600 Discussion of the Honda CBR 600F1, Honda CBR 600F2, Honda CBR 600F3, Honda CBR 600F4, Honda CBR 600F4i, and Honda CBR 600RR Motorcycles.

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post #1 of 11 Old 07-30-2017, 8:29 PM Thread Starter
 
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Idle keeps mysteriously lowering while riding

Hello all!
I have 1991 honda CBR 600 F2, This bike does have a manual idle adjustment knob on the side of the bike. So the problem is after starting and warming up my bike for 15 minutes or so i adjust idle to around 1100RPM. I ride for 15 or 20 minutes and when i come to a stop my idle is down to around 600RPM. So i have to keep adjusting this when I stop at a light or a sign. I am wondering if anyone has a idea or fix. I think it may just be a loose connection since it is a bit older and maybe i should put something on the screw threads to help it from moving? I am not sure if a vacuum leak would cause the idle to constantly lower but i may be mistaken. Any help in banishing this ghost/ demon from my bike would be greatly appreciated!
Thanks, Bo
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post #2 of 11 Old 07-30-2017, 11:59 PM
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Re: Idle keeps mysteriously lowering while riding

Hi Bo, welcome to Fireblades.org

How long has this been a problem? Is it a new problem? How long have you owned the bike?

The idle adjuster should have a spring in between it and the throttle stop on the carbs. It keeps it from loosening. That could be your problem.

You shouldn't have to warm the bike up for 15 minutes. 2-3 minutes MAX on choke, then off choke and it should stay at idle 900-1100 rpm, or whatever your manual says.

If it's not the idle adjuster, I would venture a guess your carbs are messed up on the idle/slow circuit, and they'll need a cleaning.
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post #3 of 11 Old 07-31-2017, 3:20 AM
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Re: Idle keeps mysteriously lowering while riding

I've just replaced the complete idle control cable assembly on my F3 and Ian is right if the spring is missing, engine vibration will cause the screw to undo and the idle to drop, so firstly I'd remove the fuel tank and check.

The bad news is that I don't think the screw Spring is available separately and the complete idle cable is difficult to source, I managed to get one via David Silver Spares here in the UK for £20

However you might get lucky and a screw out of a biro may do the trick.
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post #4 of 11 Old 07-31-2017, 9:54 AM Thread Starter
 
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Re: Idle keeps mysteriously lowering while riding

Yeah that spring sounds like a great step in the right direction. I have only had the bike for 4 months, It was a friends bike and he mentioned that he had a hard time starting it once (he joking stated he had the fuel shut off....) and turned the adjust too far, he said that it came all the way unscrewed. He said for me to be careful not to do it, so I need to definitely look for that spring. Guess I will be pulling the tank and air box this week! thanks for some solid great advice! I will keep updating as I progress through.
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post #5 of 11 Old 07-31-2017, 9:57 AM Thread Starter
 
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Re: Idle keeps mysteriously lowering while riding

ahh The whole cable huh... Well if it's missing I guess I will have to buy one (if I can find one) or see what I can do at work.
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post #6 of 11 Old 07-31-2017, 10:42 AM
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Re: Idle keeps mysteriously lowering while riding

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Originally Posted by Iceberg255 View Post
Yeah that spring sounds like a great step in the right direction. I have only had the bike for 4 months, It was a friends bike and he mentioned that he had a hard time starting it once (he joking stated he had the fuel shut off....) and turned the adjust too far, he said that it came all the way unscrewed. He said for me to be careful not to do it, so I need to definitely look for that spring. Guess I will be pulling the tank and air box this week! thanks for some solid great advice! I will keep updating as I progress through.
Well now, seems more and more like the spring is missing. It's possible that it's bouncing around somewhere on top of the transmission or near the starter. If the cable came out, it most likely fell off.

Keep posting!
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post #7 of 11 Old 07-31-2017, 10:42 AM
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Re: Idle keeps mysteriously lowering while riding

small piece of rubber tube will do the same job, all it needs to is to hold the screw in place
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post #8 of 11 Old 07-31-2017, 4:54 PM
 
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Re: Idle keeps mysteriously lowering while riding

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Originally Posted by Iceberg255 View Post
ahh The whole cable huh... Well if it's missing I guess I will have to buy one (if I can find one) or see what I can do at work.
to the .Org! Join up and be a member of the place, it's quite possible you're gonna have a few problems with ya bike ya wife ya life anything, we deal with it all here dude, you're more than welcome to stay. Let us now how you get on
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small piece of rubber tube will do the same job, all it needs to is to hold the screw in place
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post #9 of 11 Old 07-31-2017, 7:53 PM Thread Starter
 
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Re: Idle keeps mysteriously lowering while riding

Okay so I did not have time today to start taking it apart today but I was able to sneak my camera in there and snap a picture. It is not the best pic, but I can see the cable threads and low and behold no spring....... atleast to me. Take a look at the photo use link below.
1991 Honda CBR 600 F2 Idle adjustment knob spring missing. - Album on Imgur
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post #10 of 11 Old 07-31-2017, 7:58 PM Thread Starter
 
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Re: Idle keeps mysteriously lowering while riding

Oh here is a pic of my new toy! Just would like to share, as I am planing on becoming a member when pay day hits. Still lots of things to do to the bike!
1991 Honda CBR 600 F2 Idle adjustment knob spring missing. - Album on Imgur
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post #11 of 11 Old 07-31-2017, 9:48 PM
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Re: Idle keeps mysteriously lowering while riding

Quote:
Originally Posted by Iceberg255 View Post
Oh here is a pic of my new toy! Just would like to share, as I am planing on becoming a member when pay day hits. Still lots of things to do to the bike!
1991 Honda CBR 600 F2 Idle adjustment knob spring missing. - Album on Imgur
Looks like you found your problem

And joining as a supporting member would be a great idea. We're an elite group
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