Hi All,

I have an 83 GS550ES that will shoot up to 4000-5000 rpm once it gets really hot if you twist the throttle and it will not come back down unless I put it into first gear and let it stay in low RPMs (below 2500) for around 30 seconds. I have tried so much on this bike and found quite a few problems but still the problem persists. Here is a list of everything I have tried so far:

- Checked for air leaks using a smoke machine, wd40 and an unlit propane torch with no discernable change in idle
- replaced the intake o-rings that sit between the engine and the intake boots
- replaced choke o rings
-ensured the slides were moving properly
- gave the carbs an extremely thorough cleaning and found that the pilot circuit was seriously clogged but that still didnt fix it
- set the float bowls to factory spec
- correctly gapped and replaced the spark plugs
- new battery
- the bike is currently running 40 pilot jets and 150 airjets but factory is 35 and 145 but i tried replacing those which didnt help
- I bench synced the two carbs but havent been able to vacuum sync them bc the idle is so high
- tried turning down the idle screw (obviously )
- i have the air/fuel mixture for the pilot circuit at 1.5 turns out which is what is recommended even though they are plugged from the factory but someone drilled the out. I tried turning the screws to two turns out bc i thought i might be running too lean but it runs way worse at two turns out.
-Checked the choke and throttle cables which arent binding but i oiled them anyways
- Throttle spring on carb seems to be very strong still and throttle snaps back when pulled.
- Ect. (I honestly cant think of everything at this point)

This bike is absolutely mint with only 3500 miles on it and it sat in a dudes living room from 1990 to 2020 and then i bought if off a dude a couple months ago. Im not quite sure what could be causing this bike im running out of ideas. The only other information I can give you guys is that the bike runs perfectly and barely needs the choke to start when im starting it cold, and gets much worse from there. If I dont touch the throttle when it is red hot the idle will go between 1000-2500 rpm for no reason. Again when its red hot it only shoots up to 4000ish rpm once I touch the throttle and It acts like someone is holding the throttle open. Thanks for any help in advance!

- Joe

PS: Pic of bike attached