Runaway RPM after removing airbox 2009 GS500F

[Foltzmeister]

Hi everyone, first post here and new to working on motorcycles so I'd really appreciate any help you can give me!

I have a 2009 GS500F, which unfortunately sat unused for well over a year. A few days ago my brother & I decided to get it rideable again, and with a new battery and fresh fuel it seemed to start up fine but idled weakly, made a knocking sound around 4k rpm, and white exhaust. My brother wanted to take a look at the carburetor so we disconnected and removed the fuel tank and airbox and decided to try to start it up by funneling gas directly into the fuel lines.

This is where the real trouble started; the bike started but with runaway rpm, it shot up to about 7k before we shut it off (some popping sounds were also heard). After trying again with the same results we decided to reinstall the airbox and fuel tank, but we had the same issue. After letting it sit for a few days we tried it again today with the same result.

Does anyone have any ideas on what went wrong? Is there something we could have reconnected improperly that would cause this kind of runaway behavior? Any insight you can give me would be really appreciated!

[Sporty]

Check that the throttle isn’t being held open.



Check the enricher AKA “choke” isn’t being held open.

The red arrow is on the bar  the choke cable pulls.  The arrow is pointing in the direction of “off”




The red circle is around the idle screw. Make sure the metal linkage with the red arrow is touching the end of the screw, and that the screw isn’t turned way in clockwise.  The red arrow is pointing towards less throttle (slower).

Note: I had the idle screw turned in quite a bit in that photo




Work the the throttle and the choke lever and watch that everything is moving smooth, and that it returns to idle, and no enricher/choke respectively.

Carbs  are a constant battle to keep clean, especially with ethanol blended gas. If you let the carbs sit with gas in them.... expect trouble.

Might as well learn to remove and clean carbs if you’re going to mess around with old bikes.

There is plenty of info out there, youtube, forums, etc...
Here is one link
https://www.gixxer.com/threads/understanding-carbs-rebuilding-forks-and-1100-shocks.159718/

[sledge]

Trapped or incorrectly routed throttle cable/s maybe 

[Foltzmeister]

Thanks so much for the replies, I'll definitely give all these things a shot! And learning to remove/clean carbs is definitely on my to-do list