High Idle

Discussion in '1st & 2nd Generation 1983-1989' started by Guaire, Jul 19, 2017.

  1. Guaire

    Guaire New Member

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    About 90 degrees today. Rode about 25 miles. Stopped for a bite. Came back to the '86 VF500F and started.
    The idle wanted to surge between 2 and 3 K. At stoplights I was idling at 3K. One time it stopped as I was pulling up to the light, normal idle. While waiting on the light, the idle jumped back to 3K. I rode about 20 miles and the problem went away.
    A high idle would usually mean to me that the needle and seat aren't closing right. But, intermittent?
    Wondering....
    Bill
     
  2. stubstunner

    stubstunner New Member

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    Pre-P.S. - There is always the possibility of an air leak, but from what you described, this may not be the issue. Try spraying a little brake cleaner around the boots. See if the idle surges. If it does, you have an air leak! Now for original post:

    Hey there! I've got an '85 700F - this was something I noticed when I first got mine. As the bike warms up, the idle changed. On and non FI bike, you're bound to run into this occasional "annoyance".

    A possible cause is a bad spark or an air leak. A bad rectifier can cause inconsistent spark and the idle will fluctuate. You'll notice this on a cold start. Bike starts, hits the running temp, you give it a "clearing rev" and it hangs at around 4500 rpm. The moment I cleaned the corrosion around the rectifier wiring, the issue went away.

    HOWEVER;

    The consistent rising idle in stop and go appears to be the nature of the beast.

    Assuming you don't have any other known issues,stop and go traffic causing excessive heat is most likely your root cause.

    My Fix;
    I usually reach down and turn out the idle screw. You may want to check your cooling system as well. I've had mine overheat in heavy stop and go traffic after 1.5 hours. The idle got jumpy, bike stalled. I let it cool off, got a bite and made a speed run through the Holland Tunnel. The moment my temp gauge dropped, the idle was stable and there were no fluctuations.


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    Last edited: Jul 22, 2017
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  3. Guaire

    Guaire New Member

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    Stub stunner - Holland Tunnel, I haven't been there in years.
    I'll try the sprayer and check the intake as you suggest. Also, I'll look at the reg/rectifier connections.
    On my '97 VFR750 the complex carb linkage system would hang up and the idle was reluctant to come down. With the tank off (what a trick), I loosened and lubricated the linkage, as I could then see it sticking. I didn't tighten the linkage much. Then the VFR would idle down.
    It's been in the 90s here with humidity that's deadly. Tuesday the temp will go below 90. Then I'll get to the garage and go at it. I'll let you know how it goes. Thanks,
    Bill
     
  4. Redcrow

    Redcrow New Member

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    Check your head gaskets .. Have just had the same issue on my thou... rear bank on mine has gone but front is ok. Did exactly what yours is doing
     
  5. Guaire

    Guaire New Member

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    Thanks, Redcrow. I'll check that out.
     
  6. squirrelman

    squirrelman Member

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    my advice is to check for the same heat on all headers about 30 seconds after starting. you might have a lazy cylinder thAT only wants to fire when fully heated, increasing idle speed.
     
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  7. Guaire

    Guaire New Member

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    Finally, got to the garage. The bike is running Champion RA4HC plugs. There should be a photo on this post. They running very rich. I've got a list of more to do items.
    I'll be looking for a set of NGK DPR8EA-9 plugs to get back to a baseline. Check the fuel petcock. Are all the plugs firing? How's the compression? Drain the float bowls.
    Usually I will switch my bikes to iridium plugs, but what's the point if the mix is so rich? By the way, the air filter looks good.
    My latest speculation is the needle valves have got some poop in them, and/or worn out.
    The plug at about 2 o'clock is the 1 plug, 2 is to the right, then 3. Number 4 is at 6 o'clock.
     

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  8. squirrelman

    squirrelman Member

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    #4 looks OK, but the others don't. :eek:
     
  9. Guaire

    Guaire New Member

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    The eek! Emoji is right. A plug pull and at least I found something to fix.
     
  10. Guaire

    Guaire New Member

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    My petcock diaphragm and cover are wrecked. The spring is gone too. I get to source one tomorrow. Maybe the petcock was dumping fuel. I will still have to check the carbs ... compression, and sparks.
     

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  11. Guaire

    Guaire New Member

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    We have sparks all around. Got part # 16953-ML0-034 ordered, brand new.
     

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  12. Guaire

    Guaire New Member

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    Petcock Repaired.jpg Petcock Installed.jpg I drained gas from one the right/rear float bowl. It looked ok. I got the pet cock cover replaced with the rubber diaphragm and spring. I soldered the cracked tube on top and sealed the filter. The whole at the top had a cork in it. I epoxyed the small hole in the bottom. Next I installed it with new tubing, using a Permatex between the tank and petcock.
    With a charged battery and fresh plugs, it started. I got it to rev a little bit, but it acts like it isn't getting gas.
    I removed the tank and placed it over a catch pan. I turn on the petcock and nothing comes out. If I apply a little vacuum on the hose, it releases gas for a second or two then no gas flows.
    I'm somewhat at a loss to explain what seems to be poor gas flow. Is there a plug supposed to be on the second hole in the pic? The VF got running for about 10 seconds, got weak and died. It's like I'm not getting fuel.
    I went from what seemed like too much gas, repaired the petcock, now it acts like I'm not getting gas.
    Heeeelp. Any suggestions?
    Bill G.
     
  13. squirrelman

    squirrelman Member

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    open the filler cap and blast compressed air into the fuel line from the tank with petcock set on both On and RES.
     
  14. Mind_Surfer

    Mind_Surfer New Member

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    You know as you progress along, you may want to consider adding some in-line filtration.

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  15. Guaire

    Guaire New Member

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    Thanks for all the encouragement and comments. I've done about everything I can, including lots of compressed air blowing. This problem has reached the point of aggravation. I don't want to burden anyone more than necessary. On Monday this VF is going to the shop where I used to work.
     
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