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82 CB750C - High Idle after touching throttle, no spawn of satan?

deeveeance

CB750 Enthusiast
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Portland, OR
Hey all, I received the replacement set of carbs from eBay, cannibalized the original set and set up the new one on the bike.

Fired up instantly, few pops, but smoothed out after adjusting the rod with black knob at the "bottom" of the carbs (idle screw?).

Problem is, when I touch the throttle, it hangs at 4k RPM, and won't go down, choke doesn't seem to do much, but I haven't tried extensively as I didn't want it hanging at that high RPM.

I've made sure there's a bit of slack on the throttle cable, and the others. No leaks, but it does smell rich.

This is my first carb rebuild, maybe I accidentally swapped the jets in the wrong spots? I have the stock set of 68 and 102.

Also- the "new" carbs did not have a location for this "vacuum fuel" valve, is this what some refer to as the Spawn of Satan?

20210924_132221.jpg
 
Hey all, I received the replacement set of carbs from eBay, cannibalized the original set and set up the new one on the bike.

Fired up instantly, few pops, but smoothed out after adjusting the rod with black knob at the "bottom" of the carbs (idle screw?).

Problem is, when I touch the throttle, it hangs at 4k RPM, and won't go down, choke doesn't seem to do much, but I haven't tried extensively as I didn't want it hanging at that high RPM.

I've made sure there's a bit of slack on the throttle cable, and the others. No leaks, but it does smell rich.

This is my first carb rebuild, maybe I accidentally swapped the jets in the wrong spots? I have the stock set of 68 and 102.

Also- the "new" carbs did not have a location for this "vacuum fuel" valve, is this what some refer to as the Spawn of Satan?

View attachment 11595
Hey did you ever get this figured out? I have the same problem on my bike and I think that I have the cables on the wrong end on the carb
 
Hey did you ever get this figured out? I have the same problem on my bike and I think that I have the cables on the wrong end on the carb
Could be one of multiple problems, all of which have to be diagnosed properly.

Vacuum leaks, incorrect valve adjustment, poor carburetor synchronization, incorrect idle or idle mixture adjustment, or a problem with the choke or throttle cables could all cause a very high idle like this.
 
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