Idle problems I bought a suzuki gsf 400 94´ today.. i runs like a charm, but it wont idle.. i dont know what is wrong with it. i can turn the idle screw but then the rews come down extremely slowly.. any idea what could be wrong? maybe some dirt in the carb..?

Hello, bike not running off of choke is an indication that the pilot circuit in the carbs is plugged.. the choke is a enriching circuit hence why it runs only with the choke on. When turned off the bike starves for fuel and dies. My guess is the bike has sat for longer than 4 months and the pilot jets are plugged from varnish... they will need to be removed and properly cleaned.

Possibly if moisture has got in and created rust then you have a problem. With the engine not running twist the throttle very slowly to full limit then let go the spring should snap the whole thing shut instantly. If this does not happen the cable is binding. Undo the cable at the twist grip end and get as much lube down it as possible a clamp type cable luber will help.

dont know if this is the same but i had a sj with same problem when it wwas cold it run fine but when it was at temp it cut out and revvin up and down ended up havin a new carb which was costly and hard to find now ...

It sounds like it may not be getting enough fuel to the carb(s). Check to make sure that fuel is flowing from the tank. If not, it may be a problem with the petcock or the vents on the gas cap may be clogged.

Try to start the bike while using Jumper leads. Your battery is probably flat.

If it was running fine when you got the bike it makes me wonder how you discovered the spark plugs were rotten? Clearly they weren't very rotten...

Spark plug gaps rarely need adjusting these days prior to fitting, mostly just checking to ensure a gap hasn't been closed due to being dropped is all that is needed. I am wondering if you made the elementary mistake of confusing metric and imperial measurements; I apologise if you find the suggestion insulting.

If it wasn't an elementary mistake, I think you should begin a systematic fault diagnosis by checking the spark power and quality.

Ride the bike 20 or so miles on open road. Stop and remove plug to inspect. 'Are they black or white ?


Black =rich white=lean

have you cleaned and syncronized your carbs lately ?sounds like they could be in need of some rebuilding or maybe just a good cleaning

its common on that bike that when the choke cable breaks the owners are to cheap to replace the cable and operate it right off the carbs