The Kawasaki KLX140G is great intermediate size dirt bike for teenage kids.  Good trail riding bike, electric start, choke up on the handlebars, chain is easy to adjust, oil and filter easy to get too.  Had to replace a clutch handle already when it was laid down while riding, overall a great bike.   If you take it to moto track, remember to remove the kickstand or ziptie it up, even though it has a strong spring you don't want it flopping down on a jump, seen a bad accident happen, so even though we haven't experienced that with this bike, I always take those off when the kid rides anything with jumps.

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