Bike has irratic idle issues

[Gartellhello]

A friend of mine bought a 2006 GZ250 with 20K on it. I have had the carburetor off put in new needle and seat, diaphragm and gasket. Cleaned what little dirt there was inside float bowl area, removed low speed and high speed jets, blew out the orifices. Lubed the choke cable and lever.
With choke off and idle stop screw adjusted properly when you open and close the throttle the bike would then start to run at a very high idle speed. After several minutes it will gradually begin to slow down just slightly. Readjust the idle stop screw and it would be ok for a short time before it would start to run at a high idle speed again. Then readjust to slow it down and then it would kill as it was too slow. Each time this would happen after opening and closing the throttle. The throttle cables appear to be moving properly and in correct adjustment. I then replaced the diaphragm in the petcock thinking that was perhaps causing the erratic idle situation. IT did not correct the problem. Basically it is the worst designed piece of garbage I have ever seen in all my years of engine service. I have put jet kits in 600cc and 1000cc four carburetor Yamaha's that I own. I have rebuilt Holley and Carter automotive carburetors in years past. I have rebuilt outboard motors, lawn mowers, chain saws you name it. Never have I run into a useless piece of garbage as the one on this motorcycle. Kudos to Suzuki for using someones wet dream of a carburetor being fed fuel by a petcock with a diaphragm in it.

[alantf]

Just a thought..........Check the "slide" of the choke, where it goes into the carb. Sounds like it might be sticking.

[jdavid901]

I'm no expert, but I had similar symptoms on my bike. I fixed the problem by doing several things at once so I'm not sure exactly what did it. I replaced the fuel hose, cleaned out the carb, replaced the o-rings on the starter plunger and the needle valve seat, and readjusted the exhaust and intake valves because they had gotten extremely tight.

[jonathan180iq]

It's acting like there is an air leak.

All of the experience in the world doesn't mean you haven't overlooked a small fault during the reinstall process. Retrace your steps. You either put something and it didn't seal correctly when you buttoned it back up, or in removing and reinstalling parts, something else got bumped.

Common leaks can be found in the aged vacuum lines, the air box breather hoses, and the air box drain tube (which is supposed to be sealed at the end.) Also, the needle diaphragm can very easily become pinched when you put the top back on, causing a leak.

Pilot jet?

[newtoriding]

hi my question is i just bought a 2000 gz250 an it idles hi how can i fix this problem?

[alantf]

Use the big white knob, under the carb, to adjust the idle speed (when the engine is HOT) Suzuki recommend 1200 - 1400 RPM.

[fairweatherrider]

I have a similar problem. I noticed what seemed to be a crack in the intake tube so I ordered a new one plus the o ring. I'm not sure yet what is involved in changing it. Not sure if I have to remove the gas tank. Any ideas?

[fairweatherrider]

Originally Posted by Gartellhello

A friend of mine bought a 2006 GZ250 with 20K on it. I have had the carburetor off put in new needle and seat, diaphragm and gasket. Cleaned what little dirt there was inside float bowl area, removed low speed and high speed jets, blew out the orifices. Lubed the choke cable and lever.
With choke off and idle stop screw adjusted properly when you open and close the throttle the bike would then start to run at a very high idle speed. After several minutes it will gradually begin to slow down just slightly. Readjust the idle stop screw and it would be ok for a short time before it would start to run at a high idle speed again. Then readjust to slow it down and then it would kill as it was too slow. Each time this would happen after opening and closing the throttle. The throttle cables appear to be moving properly and in correct adjustment. I then replaced the diaphragm in the petcock thinking that was perhaps causing the erratic idle situation. IT did not correct the problem. Basically it is the worst designed piece of garbage I have ever seen in all my years of engine service. I have put jet kits in 600cc and 1000cc four carburetor Yamaha's that I own. I have rebuilt Holley and Carter automotive carburetors in years past. I have rebuilt outboard motors, lawn mowers, chain saws you name it. Never have I run into a useless piece of garbage as the one on this motorcycle. Kudos to Suzuki for using someones wet dream of a carburetor being fed fuel by a petcock with a diaphragm in it.

Sounds like you're a little upset.