Kawasaki Sportsbike Riders Club - Australia - Online Forum

hey all, i have a gpx 250 2001,
i completely stripped the ass end to get the airbox out cleaned it all up, when i noticed that the carby slides dont move with the throttle when bike is turned off is that normal. i originally suspected something wrong with the tuning due to it flattening out when i hit around 4-6000 rpm and then picking up again like powerband lol, any help is appreciated cuz i dont wanna put all that shit back together to find out i gotto do it all over again. i swear they do it so u dont attempt to pull it apart and have to take it to kawasaki dealer

69gpx250 wrote:...i noticed that the carby slides dont move with the throttle when bike is turned off is that normal....

Yep its normal.

Turning the throttle with the bike turned off will only open the butterfly valves that allow more air into the carb. Since carburetors rely on vacuum pressure to lift the diaphragm and hence needles to let more fuel be drawn through the jets, you won't see any action here unless the engine is running.

I'm no expert my any means in the mystical black art of carburetor tuning, but I have messed around with them on a few ninjas and gpx 250s. If you want to play with the carbs, be prepared to pull it apart and put it back together a few times to get it right!

Have the carbs been adjusted at all or are they stock? If it's flattening out down low the carbs might be gummed up and need a clean. If you've got them apart then (carefully) dismantle the diaphragm, needles, lower assembly and main jets and give them a thorough clean. Make sure you can see through the main jets and there should be no gunk inside.

What was the throttle position when it flattened out?

hahaha yeh i thought it needed the vacuum to move the slides i was just confused cuz iv only worked with holleys and mikuni carbs lol. i dont wanna start pulling the carbs apart at the moment i will wait and take it in the next week or so and get them synchronised etc and see what the dealers say etc

throttle posistion would of been about 1/4 to 1/2 rpm about 4000--6000 it just seems to flatten like it has a vacuum leak or sumthing i checked all the lines and air box etc when i stripped it apart and couldnt see anything old or failing but will see when i take it in.


thanks for ur help much appreciated