Input needed crf125f or klx140

I dealt with this decision last year with buying my daughter a bike. Ended up getting her a KLX 140 RF. The RF model (older models were 140 G) have a 21in front and 18in rear wheels. We ride out in the desert a lot and the bigger wheels were a game changer for her confidence. The bigger wheels roll over the bumps better and are a lot more stable in loose sandy soil.
If you go KLX, open up the air box by drilling 6 1 inch holes and inserting those Uni 1' filter vents, you can buy them on Amazon. The KLX is jetted really lean to meet emission standards, (CA model), I jetted the bike to what Jets R Us suggested.https://www.jetsrus.com/FAQs/FAQ_jetting_repository_kawasaki_klx_140.ht…

I also stiffened up the forks a bit with BBR's kit. The forks are really soft, you want to stiffen them, otherwise the front will dive when braking, not good in sandy soil. If you're a handy guy you can cut about 3.5in off the fork springs and add a 3.5in PVC spacer. It's cheaper and BBR's kit is the same thing only they use an aluminum 3.5in tube.

The CRF has a 4 speed transmission, I wasn't really thrilled about that, at least last year's model was a 4 speed. If it helps, my daughter is 5"3'. I didn't realize how much the bigger wheels helped until she rode it. I can take her all over the desert. So much fun riding with my kids! It's a really fun adult bike too!

I should add, Kawasaki is the only company that offers a kids bike with big wheels. After buying the 140RF, the other bike brands are missing out! The frame is the same as a 140L, so the pegs to seat to bar distances are the same as the L model. You get the 21in and 18in wheels, a little bit longer swingarm, and the frame has extra bracing to handle the longer swingarm. If your kid fits on it, it really is a great bike!

I got a klx 140L for a play bike. I liked that it had a full cradle frame and disc brakes front and rear. Even a play bike shouldn't have a drum brake in 2022.

How big is he/what's he weigh? Trails or moto? Aggressive/competitive personality or laid back?

I am a big proponent of the KX100 with a heavy flywheel weight for newer riders. Lighter, way better suspension, manageable power. Both of those 4 strokes are heavy with primitive suspension in comparison. The KLX140 in particular is a real pig. I haven't yet seen a 12 year old that didn't start looking for jumps to hit within a few weeks and the KX100 will give him room to expand his skills. Just IMHO, but I've taught quite a few kids to ride, and most are over a 4 stroke trail/play bike in a month. Suspension is the first thing they override.

Con of the KX is premix hassle and it takes a little more TLC (top ends and cleaning powervalve) than the 4 strokes. Both of those are pretty bulletproof and require little other than gas and oil changes.

Hammer 663s

+1 on the KLX140G (or RF as otg said). I picked one up for my wife due to a CRF230F being too heavy for her, and while it's still heavy due to old technology it's been great.
Hammer makes a great point as well for the KX100 (or KTM 105 smoker) as the KLX is not well sprung as is.

A group of us have ridden these bikes on Michigan ORV trails just for fun and the 21/18 wheels make a ton of difference... the poor saps on CRF150Fs and TTR125s call mine a cheater bike LOL. Hardly hahaha

You can also swap out the klx140 forks and shock for KX100 suspension. Its pretty much a clean swap if you swap out clamps/tree withe the forks. I'm looking for a ragged out klx140 for a project bike now. can't wait to build it out!

I agree with Hammer. At 12, I'd get him a real MX bike, then tell him to take it easy at first. It gives him something to grow into as his skills increase.

KLX140l is almost 210. Crf150f is 236!! Kx100 is 168. Xr100 165. 12 years old and 95 lbs? I know what I’d buy.