Converting kx100 to kx125

[dinknshell]

So much for letting friends ride your bike. This one came back toasted. My son has an 03 kx100 and I want to put a kx125 on his frame.
Anyone know if it will bolt up properly? I have not bought the motor yet. I am making my son sit out the first few weeks of spring without his bike.
It should teach him a lesson. (I hope).
Also does anyone know if i will run into major problems trying to do this?

Thanks for any information. This is his (and mine) first kawasaki, and we love it!

[roostdoctor]

Things to consider for your swap. You will notice that the 100's ex. pipe runs on the left side while the 125 runs on the right like most bikes. Take note that that the ex. pipe on the 100 is a side exit while the 125 has a straight exit - means major mod to the forward craddle. That just for starters. I think it can be done by a competant fabricator but not easy by any means

[bikepilot]

The cases are very different. I suspect you'd have to weld in a new, custom engine cradle, possibly modify the fuel tank for more clearance and build a custom expansion chamber. Also, the 125 engine is not going to fit with the KX100 swingarm/frame pivot - some custom work of some sort would likely be required.

I'd suggest that if its more power you need you go with a bore and stroke. You can get to 112cc IIRC this way and it will run quite well.

good luck!