Carburetor issue

I drained the fuel last fall, and just pulled the bike out to get it ready for the season. I dropped the bowls, pulled the needles and cleaned everything with carb spray.

Now it will only run at full throttle.

Am I going to have to pull the carbs and deep clean them... again?

Idle circuit clogged after sitting empty all winter?

Or is there something else going on?

(1982 Yamaha XJ650 Maxim)

 

Well, I took the carbs off, dismantled them, cleaned them, everything seems to be as it should be, however...

It'll only run at high idle... any ideas?

The idle adjustment screw isn't even touching the throttle linkage. It is literally set to low to no idle speed, but only starts and runs at high idle.

I'm lost as to what it could be.

 

Has the engine been synched (running engine, vacuum-synch) since the carbs have been rebuilt/installed?

 

Yes.

 

Is the throttle cable junction (at the carb linkage) hanging up on the cylinder head fins?

Other than that, typically a high idle is caused by an overly lean condition, i.e. a vac leak somewhere.

 

The throttle cable and linkage is exactly as it should be.

I think I just have to close the butterflies down a bit.

I'll pull the carbs tonight after work and check them.

 

If you removed the butterflies, did the plates get properly centered when putting the screws back in? When you reattach them, you want to put the screws in just barely snug enough to hold the butterfly plates flat against the shaft, then slowly close them and allow the plate to self-center in the bore before tightening. There is a little bit of slop in the screw holes and if you don't get them properly aligned before tightening, you can get some leaks and/or it may prevent fully closing.

Also note the position of the sync screws. Should be somewhat centered and roughly the same on each one to start with. If one is cranked too far or not far enough it can hold others open. I usually bench sync mine by getting them all fully closed, then adjust the idle screw to where the first one just starts to open, then adjust the rest to be the same, then once they all start to open at the exact same time, I turn up the idle slightly, so they are all cracked just a smidge. (the technical term) If I remember right, I think the butterfly plate will partially cover one of those small holes in the bottom of the bore. If you can't see those holes, something isn't right.

 

It was the butterflies.