Bike lurching at stable revs

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Devan78
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Bike lurching at stable revs

Post by Devan78 »

Hi all,

I've got a small problem, not sure what to make of it. The engine works well and sounds healthy while I'm accelerating, but when I stop opening the throttle and maintain a constant speed, I feel minor blips in power, sort of little lurches or flat spots... not enough push me around, but just enough to be annoying. Roll the throttle again and they go away, until I stop accelerating again. Perhaps related, I've also noticed that if I get the revs high and then go stop in neutral with no throttle the bike idles quite high but eventually starts coming down to a reasonable level in stages (usually 2 or 3 minor dips in revs). Unfortunately my rev counter isn't connected so I can't give numbers.

Any ideas?

Devan
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Varmint
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Re: Bike lurching at stable revs

Post by Varmint »

That sounds like a lean condition. Do you have stock jetting? What bike are we taking about?
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Deseret Rider
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Bike lurching at stable revs

Post by Deseret Rider »

Varmit is probably right-----I'd try raising the needle one clip though before I started changing jets.
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Devan78
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Bike lurching at stable revs

Post by Devan78 »

Took the bike out for a solo ride into the middle of some rice-paddys, and promptly lost all power about 10km from the nearest village. Got a "Vietnamese tow*" from a local farmer back to the ferry. Met my mechanic in his pickup, and went back to the shop. Turns out the spark plug was completely shot. Fitted a new one, and it seems to have solved the problem.

*Basically flag down the first guy you see any ask him to push you by putting his foot on the back of your bike, luckily I had my pillion pegs on!
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Bike lurching at stable revs

Post by Deseret Rider »

If the bad plug was black and greasy ---it might be that you are jetted to rich instead of lean. If that's the case you might want to drop the needle one notch instead of raising it as I had suggested earlier. If you have continued problems with spark plug failure then you might want to pull the carb and let us know what the main jet and pilot jet sizes are? What is your elevation there?
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Devan78
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Bike lurching at stable revs

Post by Devan78 »

Deseret Rider wrote:If the bad plug was black and greasy ---it might be that you are jetted to rich instead of lean. If that's the case you might want to drop the needle one notch instead of raising it as I had suggested earlier. If you have continued problems with spark plug failure then you might want to pull the carb and let us know what the main jet and pilot jet sizes are? What is your elevation there?
The plug was definitely black and greasy... I'll look into it. Elevation is about 2 foot on a good jump, but I've only been riding two weeks :P

Seriously though, Saigon is about 20m above sea level.
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Bike lurching at stable revs

Post by kyledsmith87 »

I have just jetted out the exact same condition. It was too rich, going 1 leaner on the needle cured it.
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