Fast uncontrolled idle after carb cleaning, rebuild, throttle or cable change.

[JustEnough]

I seem to see a lot of posts about this problem and found one likely cause.

The problem might be a slide spring that is too short, or the slide spring is missing. My experience was with a Keihin PD carb, but it could probably happen to any round slide carb.

I had a problem where two different carbs would idle too high. I knew that if the slide was is in backwards it would run at wide open throttle. This was different because it would drift up and down, mostly up, like the slide was floating in the carb body. After some parts swapping, I figured out that the spring I had in the slide was too short. I switched to a longer spring and it idles great now.

If the slide spring is too short or missing, the slide floats up causing a fast idle. One way to tell that the slide spring is too short is when you compress the spring to remove the slide from the cable, the cable end does not push out of the slot in the slide, you have to use a tool like a scratch awl to get the cable end out.

This problem could show up from any change that allows the slide to move farther than the slide spring is long.

[fabiodriven]

This problem is caused by many different things, but far too many times guys post about it without taking a good look first. 9 times out of 10 it's something incredibly simple.

One very common cause that guys overlook VERY often is when the main jet needle misses it's seat and gets caught up on the base of the carb bore, thus holding the slide wide open. It's very easy to miss the hole (ha ha) and also easy to diagnose if you take your time and open your eyes.

[Scootertrash]

Lol Fabio!

[ZacH_GrifF]

I know when mine did it, it was due to the cable was not secured into the throttle housing so it would move in and out of the housing. Ziptide the cable to the handlebar and it fixed the problem.

[captainweezy]

Im going thru this roght now with one of my 70's. worst part is having to take everything off and on until the problem is solved.

[ColtonGG33]

Im going thru this roght now with one of my 70's. worst part is having to take everything off and on until the problem is solved.
I know I'm having carb problems too and it is so annoying taking everything on and off, so I just took the gas tank off put it on rear plastics so the gas line is still hooked up, it's a lot easier doing it that way, until it works

[Dave8338]

One other thing to check: Did the o-ring slip off the intake/head side of the carb and you now have a massive air leak. If so, or even if it cracked in a few pieces from age and fuel vapor, it will cause the engine to run lean and this will show up as a hanging idle. :idea: