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Discussion Starter #1
Ever since I've had this bike (and through 2 carb rebuilds) I've always found that when I roll the first bit of throttle one while the bike is in gear it comes on with a jerk. The rest of the throttle range is smooth, just coming off idle jerks if in gear. Is this somewhat normal?

-Robert
 

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Ever since I've had this bike (and through 2 carb rebuilds) I've always found that when I roll the first bit of throttle one while the bike is in gear it comes on with a jerk. The rest of the throttle range is smooth, just coming off idle jerks if in gear. Is this somewhat normal?

-Robert
I don't know what it is, but it is not normal. It may not be the carbs. Since you said it does this with it in gear, it might be something wrong with the transmission or final drive, like it is taking up lash in the drive line when the rpms increase.
 

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FREEBIRDS MC CENTRAL NY
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Does it make a little noise at first?does it do it when warmed up?
 

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Discussion Starter #5
No, no noise. I probably didn't explain it well. So if I'm decelerating in gear, not touching the clutch and then want a bit of power, if I roll on the smallest amount of power it comes on with a lurch. After that I can continue to advance the throttle and further acceleration is smooth. Its just that first bit when its under load. Its definatly not clutch or transmission related; it feels like the power just doesn't come in smooth. It feel more like when your 15 year old is driving the car and you say 'give it a bit of gas' and they give it too much and you get somewhat thrown in the back of the seat. My bike has always done this and I assumed it was normal.

-Robert
 

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Dr. Vulcanstein
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Inner cable inside throttle housing may be crusty. When it reaches certain tension suddenly releases take of and relube or replace maybe.
 

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there is a certain amount of 'play' or 'slop' in the transmission and rear gears.. including the rear splines.. normally not much, but as the bikes get older and wear, just like a car, when you go from the coast side of the gears, to the drive side, there may be a jerk.. that might be what your feeling.
 

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If the throttle is harder to turn just above idle, I'd say it's a frayed cable, or cables. Just saw some cheap on Ebay.
 

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Discussion Starter #10
Inner cable inside throttle housing may be crusty. When it reaches certain tension suddenly releases take of and relube or replace maybe.
That's definitely what it feels like. However, if I have one hand on the throttle and the other on the carb I can't feel any binding as I roll the throttle on. It feels really smooth. The bike only has 15K miles so I wouldn't think the gears would be worn.

-Robert
 

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..have a vulcan good day!
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That's definitely what it feels like. However, if I have one hand on the throttle and the other on the carb I can't feel any binding as I roll the throttle on. It feels really smooth. The bike only has 15K miles so I wouldn't think the gears would be worn.

-Robert
I replaced ALL my cables @ 10+ K miles.....
....just sayin'

:smiley_th
 

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That's definitely what it feels like. However, if I have one hand on the throttle and the other on the carb I can't feel any binding as I roll the throttle on. It feels really smooth. The bike only has 15K miles so I wouldn't think the gears would be worn.

-Robert

To check the throttle assembly and cables, with the engine off, open the throttle all the way, and release it. It should snap back instantly. If you haven't done it recently, it wouldn't hurt to lube the throttle assembly and cables, and make sure everything is adjusted right. When you are done, with the engine at idle, turn the bars from full right to full left to make sure the engine speed does not increase.

It is also possible that you are noticing something that most people ignore. CV carbs, like on the Vulcan, do tend to have more of an abrupt (as you put it "jerky") throttle response than non CV carbs, both on and off throttle. What actually causes it is a brief hesitation in throttle response. Since a CV carb must "wait" for engine vacuum to pull the slide up, you'll get a delay in the engine's response when you twist the throttle open, like the throttle is "disconnected" from the engine. You open the throttle, nothing happens for a fraction of a second, then it kicks in. It's one of the reasons I prefer non CV carbs, but I have gotten used to it, and these days I'm just glad to have carbs of any kind.
 

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Discussion Starter #14
I ran some tri-flow down both cables at the throttle. I used the tri-flow we use for aircraft cables, bell cranks. It seems like its made a difference. I may be being extra careful on reapplying throttle over engine braking but I do think its smoother. The throttle is definitely not bound though as I currently actually have a bit too much slop in my throttle. I was surprised though because when not running there appeared to be no binding feeling the carb while moving the throttle.

I also wonder if my slightly excessive slop in the throttle could be causing the throttle to slighly bounce on slightly bumpy roads. When the road isn't smooth I find very subtle pulsing. Its likely mostly caused by poor rear suspension not creating optimal road contact but I'm wondering if some could be throttle bounce.

-Robert
 
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