What may be wrong with a kx 250 that you can hold the throtle wide open and all it does is idle it will not even begin to run?

Answer 1

Answer 1Could be the clutch needs adjusting or it isn't going into gear. Answer 2Obviously answer 1 did not understand the question in which the keywords are: "...throttle wide open...all it does is idle..."

The proper answer is that the linkage [a "push-pull" cable] between the handle grip throttle and the carburetor has somehow become disconnected.

A push-pull cable is made of two parts: a movable solid wire inner cable, inside of a fixed "wound wire" outer cable, usually covered with a rubber or plastic protective sleeve. At it's lower end, the inner cable is attached to the carburetor throttleplate arm, and at it's upper end, to the throttle grip on the handlebar. The connection at the grip end is linked to the grip by a slider/follower which is pulled through a spiral slot inside the grip. This mechanism converts the rotary hand action on the grip into linear action at the carburetor, in order to move the throttle plate arm on the carb.

There are three [that I can think of] possible causes for failure of this linkage:

1. The set screw which secures the throttle cable to the carburetor throttleplate arm has loosened. IF the carb is an SU type, the lower end is terminated with crimped-on "barrel," or cable bushing which has become disconnected.

2. The inner throttle cable has broken.

3. WEAR on the spiral actuating slot or the follower in the throttle grip, has allowed separation.

Item one can be corrected by reattaching the inner cable to the throttleplate arm, properly adjusting, and tightening the set screw.

IF the carb is an SU type, and the barrel or bushing has separated, or the cable has broken, it will be necessary to replace the entire cable [inner and outer come as a single assembly].

If items two or three are the cause, it will be necessry to REPLACE the cable AND/OR the handlebar throttle grip assembly.