300EX To 250X Swap

[thyman17]

Hi i was wondering what i needed besides motor to put a 250X motor in a 300EX frame. And how hard it would be to convert seems like there the same chassis and engine mounts but i need a different wiring harness for sure right?

[the Z Man]

You could probly use the 300ex harness, if you were going to a 300ex you would need that but that is for the electric start, I believe everything should work with what you have, I know for a fact everything bolts up......

[rollinlow]

im in the middle of this swap right now the wiring is not the same cant be used but the motor bolted right up

im havent trouble with not getting spark i think its a ground problem

[the Z Man]

I think everything works but different color codes, just need to trace wiring from a manual, you can probly eliminate a few things form the 300ex harness, but the essentials should be there to use.. just a thought, follow from the stator and find the hot wire and cross reference it to the other colors.

[rooster300ex]

You need a 250x harness.

[MTDman11]

wait isnt the 250x the same thing as the 300ex but with a smaller motor. why wouldnt u keep the bigger 300ex motor in it?

[thyman17]

I blew the 300EX motor to pieces and i bought a 250X motor for 250 bucks so im gonna put it in after throwing in a new set of top end gaskets. As for wiring goes can i use the wiring from the 300? i still have the motor and all the electronics from it are new. Ive transplated motors before but this one seems too easy what all do i need if someone can tell me step by step how to wire it with the 300 harness that would be greatly appreiciated. Im going into the army so i would like this done before i go so i can have one last ride with my buddies before i go. thanks for all your help..

[bwamos]

Originally posted by thyman17
I blew the 300EX motor to pieces and i bought a 250X motor for 250 bucks so im gonna put it in after throwing in a new set of top end gaskets. As for wiring goes can i use the wiring from the 300? i still have the motor and all the electronics from it are new. Ive transplated motors before but this one seems too easy what all do i need if someone can tell me step by step how to wire it with the 300 harness that would be greatly appreiciated. Im going into the army so i would like this done before i go so i can have one last ride with my buddies before i go. thanks for all your help..

No, you really need a 250x wiring harness and CDI.

DC system vs AC system. Much easier and cheaper to just get a 250x harness off of e-bay.

[tecate87]

yes, you will need the 250x electronics if you are running the 250x engine. cdis, stators, flywheels are different,

[thyman17]

Ok i gave up tryin to wire up the 250X motor so i decided to rebuild the bottom end of my 300EX motor and throw the piston head cylinder on it. Works like a charm started right up first push of the button but i had to adjust the clutch. Also what would cause a broken Key on the crank? too much compression or just an old key? I had a bunch of new ones so i through one of them on. The 250X motor was bored .050 over and had a new piston cam and valve train so i thing 250 for the motor was a good deal .. ill let you know how it goes..