I remember some more about my cable... On my particular 220's cable, there was some excess flash on the lug at the twist grip end of the throttle cable. Under close inspection, this flash could catch on the throttle housing, or cause the lug to bind, etc. It was certainly a possibility for my bike to have a stuck throttle with those particular components.
I removed the described flash, and never had a problem with the 220 all last year.
The other mentioned potential causes are certainly possibilites as well. But, as one member pointed out, this throttle sticking seems to be a newer KDX thing.
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-01 RM250 (mine) & 01 RM125 (kid's)
-Senior A Enduro and Hare Scramble Rider.
"Yep, that 14 yr old A Class rider is MY kid; He learned to ride from ME!!"