5k idle????

[havoK]

I have a 78 gs 750, 4-1pipes, k&n filters, rebuilt top end...
Carbs are jetted and synced, idle on fire at 5000rpms, I have the idle knob all the way out, and all jets should be right, not sure why
Bad cable?
Any other reasons this could be?

[koolaid_kid]

I have a 78 gs 750, 4-1pipes, k&n filters, rebuilt top end...
Carbs are jetted and synced, idle on fire at 5000rpms, I have the idle knob all the way out, and all jets should be right, not sure why
Bad cable?
Any other reasons this could be?

That usually indicates a very lean condition, normally by some sort of leak(s) in the intake system. O-rings, intake boots, air filter boots, etc.
Or slides stuck open, but that is a bit more rare.

[Dogma]

George, I'm not real familiar with those carbs, but with the idle backed all the way out, shouldn't the butterflies be completely closed? I'm thinking a tight or dodgy cable.

[havoK]

I talked to a friend, he said it has to be a cable, going to try that, we will see

[koolaid_kid]

George, I'm not real familiar with those carbs, but with the idle backed all the way out, shouldn't the butterflies be completely closed? I'm thinking a tight or dodgy cable.

You may be right, I keep thinking about CVs. Seems like you could pull the carbs with the cable attached and check. It might be something as simple as a mis-routed cable. That was also a push-pull arrangement, so either cable could be the issue.

[Nessism]

You might want to check the newbie mistakes thread linked in my signature and see if anything rings a bell. No. 1 most common reason for hanging idle is an air leak from the intake boot O-rings.

[BigD_83]

I talked to a friend, he said it has to be a cable, going to try that, we will see

Do the rpms change when you rotate the steering from left stop to right stop? That'd point to a cable issue.

You want to have a little slack in the throttle cables at the carbs. If they are tight, check the adjustment locknuts first, the cable routing second. I can't picture the linkage on the VMs, but the CVs have a little bracket the cable locks into at the carb rack, and that can cause problems with cable tension if the bracket gets bent.

Another place to look is in the throttle tube on the grip. If you've had it apart, the cables have an annoying habit of popping out of the groove when you are not looking. I've seen that as a cause of a racing idle more than a few times.

[havoK]

Got it, zip ties and throttle cables=bad mix

[koolaid_kid]

LOL. Glad you found it.
To modify your statement, tight zip ties and cables = trouble. You can use them, but the cables need to be able to flex as the inner cable slides up and down. So if you use them (I do) make sure they are nice and loose, allowing the cable housing to move as the inner cable moves up and down.
Congrats, and ride on.

[havoK]

Yeah, they were on tight, must have been twisted on the top end rebuild, going to replace them now just to get away from future issues, thanks for ideas
Ride on as well