Warms up then idles up to 4,500 rpm?! '83 GS750

[Guest]

I'm working on getting my GS sorted out and here is where I'm at:

It starts right up with full choke, even after sitting for five days while I was out of town. Wants to idle around 2,000rpm on the choke. Once it get warm enough to idle without the choke it goes down more towards 1,000rpm but then almost always dies out. It sounds slower than 1k too... odd.

Once it gets good and warm (3-4min the gauge starts to come up towards 160) if I blip the throttle it seems to hang up at around 4k when I let off....and just idles there forever...well as long as I let it run anyway.

I've tried using MAPP gas around the carbs and both sets of boots to check for leaks, pushing on the throttle linkage to make sure it isn't hung up, nearly burnt myself backing out the throttle stop screw, set more slack in the throttle cable, tapped on the carb bodies with a hard plastic rod to try and free any stuck pistons (eveything felt fine when I put them together).

Vavles and float heights are set to factory spec. Carbs are newly "dipped" with new internal o-rings from Robert Barr, new intake and throttle shaft o and x-rings from me. I bench synched them before installing with a small drill bit. Air screws are set 1.5 turns out from lighhtly seated.




Any ideas or links to the thread I was looking for but didn't find?

/\/\ac

[Macmatic]

Ok. I don't know how cold starts will be now....or how I fubar'ed this in the first place but the high warm idle was due to the idle control screw being in way too far. I turned that POS back out until the idle dropped to about 1500 and started synching the carbs...

Now I've got 1, 3 & 4 at about 25cm Hg but can't see to get #2 to budge off 12-14cm Hg. The petcock vacuum tap is blocked off and triple checked. I've got a spare set of carbs to look at but I still can't see how to adjust #2 without putting the others way out of line.

/\/\ac

[LW_Icarus]

Are the 83 750 carbs VM or CV?furthermore does it have one carb that the other three get adjusted to? Ill bet it does, just synch number two to it and then 1 and 4 to those. is the little adjustment screw turning properly? I had one that needed removed and cleaned to get it set accurately.
Is the compression good on all four cylinders? and are the valves set properly? those can affect how much vacuum a cylinder is capable of producing, otherwise its just a matter of getting two set to three, and then making 1 and 4 work on that.
if all else is right they should cold start just fine, mine can sit 10 days and start within a second of touching the button, on a thirty degree day. getting it warmed enough to ride right is a different matter

[Macmatic]

Thanks for the input LW,

I see now that the center adjuster kind of makes 2 & 3 "see saw" on the carbtune. Turn it one way and 2 is higher, the other way and 3 is higher....find the right balance....mess around for 20minutes or so trying to tighten the locknut with the right tool...go order the tool and come back to finish the job.

So now all four are within 1cm Hg of the others 1,3 & 4 are even with 2 being very slightly lower. Good enough until I get the adjuster tool!

Tomorrow I'll get some road miles on and see how it looks/feels under load.

/\/\ac