Rev goes high gradually on idle and stays high

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moto_ram
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Rev goes high gradually on idle and stays high

#1 Post by moto_ram » Mon May 25, 2020 6:33 am

I have a 94 Suzuki DR125SE. On idle it revs higher and higher gradually on its own. Also, when I open and close throttle it stays at high rev and takes forever to come down. I have checked the throttle cable, boots for vacuum leaks, adjusted the air/fuel screw on the carb, even changed carb to a totally new one and the problem still exists. The spark plug is black so I assume it's running rich. However, playing with the carb didn't seem to fix anything. It starts just fine.
I have not looked at valve clearance yet but not sure if it's got anything to do with this.
Any advice is appreciated

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BikerGran
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Re: Rev goes high gradually on idle and stays high

#2 Post by BikerGran » Thu May 28, 2020 10:47 pm

When you say you've checked the throttle cable, what exactly have you checked? I had this problem on my Kwak GT550 and I lubed the throttle cable which made no difference. It turned out to be the linkages and return spring gummed up with old oil and dirt. Cleaned it up with a degreaser and a brush, put fresh light oil on it, solved the problem.
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Shebee
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Re: Rev goes high gradually on idle and stays high

#3 Post by Shebee » Fri May 29, 2020 6:35 am

Does it have a choke? Running rich would be a symptom of choke on?
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fatboy
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Re: Rev goes high gradually on idle and stays high

#4 Post by fatboy » Fri May 29, 2020 2:06 pm

Check the air filter/housing for obstructions
Has the end can been messed with as a lack of baffles enriches the mixture
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Ben
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Re: Rev goes high gradually on idle and stays high

#5 Post by Ben » Fri May 29, 2020 4:28 pm

BikerGran wrote:
Thu May 28, 2020 10:47 pm
When you say you've checked the throttle cable, what exactly have you checked? I had this problem on my Kwak GT550 and I lubed the throttle cable which made no difference. It turned out to be the linkages and return spring gummed up with old oil and dirt. Cleaned it up with a degreaser and a brush, put fresh light oil on it, solved the problem.
Similar happened to me on my Hypermotard.

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