High idle on a 91 Kat 750

[KatanaJim]

Hey everybody!,
I am new here but I have already found a butt-load of excellent info!
I have a project bike I am putting together, but have run into a little snafu.
The bike starts fine with the choke. The RPMs will raise, as they should then I turn the choke off. It Idles perfectly for about a minute, then the RPMs begin to climb. When it is warmed up, it idles @ about 3000 rpm! Adjusting the idle screw does not help, I can make the idle go higher, but not lower. The throttle cable is not binding, and is adjusted. Could this be an air/vacuum leak? The previous owner "jetted" the carbs, could the idle jets be too big? Any input would be appriciated!

[Anonymous]

When my carbs were outa sync, the revs would shoot up.

[KatanaJim]

Thats sort of good to hear. If I can fix the problem without tearing into the carbs, that would be great!
A good sync'n is on the top of my list...

[md86]

Our project is doing kinda the same thing . Supposedly it's either....
A) An air leak somewhere
B)Clogged pilot circuit
C)Cable binding , or
D)Gremlins
Hope you figure it out .

[Anonymous]

Yeah...mine was:

1. #1 carb idle screw did not match the other 3 due to missing rubber gasket
- so, engine would rev up when sync was attempted as other 3 carbs needed to rev higher to keep a good vacuum

so

check idle scews (2.5 to 3 turns out)
check vacuum leaks
sync

[md86]

"Idle screw rubber gasket" ? Help me out here . Is that the pilot screw o-ring maybe ? There something I'm missing ?

[Anonymous]

yep

[md86]

Huh ?

[Anonymous]

sorry, yep as in the pilot screw o-ring

[md86]

Gotcha . Interesting . Jim's bike was doing the same thing . Not sure how he solved that . His pilot screw would back itself out over time . But I thought the little metal washer went over the o-ring , so the scew doesn't "see" the o-ring . Actually , it's the spring that the screw sees , ain't it ? Been a few weeks since I've torn apart a set of carbs ....

[Anonymous]

Yeah the spring...but without my o-ring, the spring was kinda loose, and that enabled the screw to turn with just engine vibration.

[Black_peter]

Big 10-4 on Kickit ...

I would sugesst this:

1.Valve adjustment..
(who know when it was done last)

2. Carb clean.
(At the very least pull the F/A mix screws and spray in there, then spray all the little ports you can see
with the air box off)
The o-rings can be tricky and damage easily..
They are cheap too!

3. Carb sync.
(IMO usless with out step 1 and 2)

[KatanaJim]

Carbs were just "redone" according to the previous owner. Valves are definatly on the list. I am going to get it in "runable condition" thn take it in to the shop for the valves...

[Black_peter]

Valves are pretty easy on the Kat..
For what a shop will charge you could buy:
A Suzuki factory manual.
A carb tool.
A valve adjustment tool ( not really needed)
etc..
(I'm only up to $200 or so!)

[KatanaJim]

Black Peter, your right! If I am going to stick to my low budget theme, I may just try it myself. Are the shims expensive or hard to get? They do use shims right?