putting the trx300 on 250sx

[aldcgd]

ok guys I am thinking of putting the trx 300 motor on my atc 250sx. what all do I change and what harness do I use. will it make enough difference to be worth it

[aldcgd]

anyone know if this work .swap heads only

[TheRealFatShady]

Stroke in longer, so the wrist pin locations are supposedly different. *(Only repeating what I've heard.....I've heard the same for 300ex/250x engines, but supposedly those pistons interchange??? So it may not be true)*

Basically, take off the right side cover. Take out clutch. You need to remove the output shaft (where the driveshaft connects) and slide it out through that side. Basically to do this, turn the engine on the side.

DO NOT RUSH! There's a thrust washer on the end of the shaft, closest to the ride side case you took off.

Basically, o=shaft, g=gears, w=washer
[OoggggW] Sorry if that's hard to explain, but don't drop that washer down.

Also, the hole on the end (you'll see when you take right side cover off) needs to be made a little larger with a drill. Oil feed tube gets bent to fit that as it's maybe 1/4" longer than the 300 one.
And there is one gear +2 clips on the letter diagram above, right where "O" and "o" meet. You do NOT need them. It's a c-clip, gear, c-clip. The 300 does not use those.

Here's the end of the shafts, notice one is so much smaller?

Here's how your engine (300) will look. 250sx engine too if you want to use it again so you don't lost that thrust washer.

And here's what they put in place of the shaft while sliding it out. I used a pipe that was the right diameter. Pretty much every gear in the bike sits on that shaft, so you better not let them fly everywhere!
\

Then for wiring, the guy who posted those pics originally I think made one out of the TRX and SX harnesses. I am just using the full TRX setup whenever I get my case tig welded, my frame fully fixed and painted, and maybe fenders.

[aldcgd]

k thanks a lot. I may come out better just bore it out. I am pretty sure the head only is bad on the 300. so think I will just do a little to the 250. thanks a lot for the pic and info. I was just running some ideas around. I just had a 300 that runs good but bad rear end and was trying decide what to do with it. LOL. I would rather have the sx going. got my eye on a 350 x and a 250 r.

[TheRealFatShady]

I'd use the TRX300 engine. The swap is actually really simple.

Plus, there's so many more options for upgrades. Cams, gear reductions for torque, big bore kits, stroker cranks, carb/exhaust/etc. It's not as complex as it looks. Just don't lose that washer.....and don't let anyone touch your engine that may drop it and crack you case like mine!!!

[aldcgd]

so basically I just have to switch output shaft and it will work. I still got the issue with the head. someone tried to shave it before I got it and I think it is uneven. that's why I wondered about the 250head.