Tx300 vs Tc250 chassis

I’m fairly certain that the actual frame, shock position, etc., is identical on both models.

I thought those chassis were identical...

Valving and spring rates can do that.

Also, the TX has a much more mellow power curve with more torque and taller gearing.
A bike with punchy bottom end and low gearing will be easy to upset the rear suspension.

Chain-torque has an effect on the rear suspension feel. The difference in gearing (especially rear sprocket size) between these two bikes will result in a different rear end feel due to that chain-torque effect.

I've ridden both of these and really didn't like much about the TC250 on a motocross track. The TX was a pleasant surprise. The suspension was too soft on the 300, but the engine was excellent and delivered enough torque that the taller gearing made up for the short power curve these bikes have.

Yep exact same chassis. The TX has a bit more weight due to the larger tank, e-start, kickstand and such. Just don't fill the tank all the way for MX and it'll help. The suspension is a lot softer on the TX, but it's pretty adjustable. I added 8psi to the forks, 1-turn on high speed compression, and 3-clicks on low speed for MX vs my off road settings and found it pretty good. Still very plush and eats braking bumps for lunch, but still also a bit soft and can blow through travel a bit on steep jump faces, so watch your feet if a face is steep and rutted. I only did one day on a MX track and didn't have time to mess with further settings. I suspect going in further on the compression adjusters would be helpful.

Same chassis. Different suspension valving(very different). Motors are also pollar opposites. The TX has less timing, less compression, wider ratio gearbox(no thanks), heavy estart and a crank that is nearly 1lbs heavier to accommodate the charging system & heavier flywheel.