Waiting on some wheel adapters to put the bigger tires/wheels back on it as I used the original axle due to the damage to the other one. It still has good speed and torque but not as radical as with the 200cc motor. The biggest difference with the motors is the 125cc has a #420 chain vs. the #520 on the 200cc motor. I only had a few choices with the sprockets and went with a 44t, the factory had a 50t. It seems to perform well with this gearing but the bigger tires may change that. It doesn't have anywhere near the top speed- maybe about 35mph now, that's still a good speed for our trails and it still climbs well. Here's a quick vid. of the 1st run with the TRX125 (a wire came disconnected) motor:
https://www.youtube.com/watch?v=2hShxalyTMY