Bike revs on its own to around 3-4k rpm

[OnePhate]

Hey, I finally got around to starting up the bike today. She starts perfect on the first turn off the starter with no choke (new plugs and filters) but after about 5 minutes at idle she decided she wanted to rev to 3k and 4k if I don't turn her off, again choke or no choke she does this even when riding. When started goes to about 2,500 for 5 seconds or less and then settles at 1,250 for a while.

TL;DR Will idle at 1,250 until warm then surges to 3-4k

 

[OnePhate]

I might have found the problem... I forgot to hook up the vacuum line to the tank, and just had the petcock set to "on"

 

[Pork Chop]

I think that would do it.

 

[drewpy]

yep, as Charlie Chan says, " Sirry irriate"

 

[OnePhate]

Woops, seems it wasn't the problem after all! It persists again, I checked for leaks at the boots using starting fluid, and that didnt show up so i went a little more thorough with an unlit propane torch and couldnt find anything. Hmmm...

 

[why walk]

When mine did that it was just because the throttle stop screw was too far in, depends what choke setting your using though.

 

[HoughMade]

What are your idle mixture screws set at? As you have surmised, that is characteristic of a lean condition.

 

[bentwrench]

Add in that it happens after you've warmed up the engine, and you're likely looking at a leak that you'll only find when hot. Something is warming up and expanding, and then allowing a leak. It's likely not anything to do with the carbs (unless your carbs are getting hot, in which case you have other problems.)

I would check things like head gasket, and valve tappet clearances. Anything you can think of that's getting hot, and then allowing a leak.