Swapping in a TRX300 engine into a 250ES

[86BigRedRider]

What exactly do I have to do to put the 250es side gear output case into a TRX300 engine?? I'm making a ATC300ES! I know that the gear case will swap out, but I'm not too sure how to do it and what parts/gaskets will be required. I have the 300 engine, a new shaft boot, the 250 output case and a gasket set for a 300. I work on Honda CARS! not trikes and have NEVER opened up a cycle engine. I would enjoy some expert or hands on knowledge on this. THANKS!!

[the great gazoo]

There is a member here (British guy, I think) who put a TRX300 engine in a 250SX . If memory serves, he had to machine a spacer to get the final drive to line up. Real cool build with lotsa pics.
Do a search for 300SX & I think you'll find it, TGG.................

[TheRealFatShady]

You have to take off the side cover, both clutches, oil line, kicker gear assembly, etc.

Then the unbolt the output shaft, and push it out. You need to use a pipe or tool to take it's place from the side where you removed the clutch; I think 3/4" piper or smaller will work. Basically, there's a thrust washer where the gear closest to the output shaft meets the case; you must keep it there. If you slide the shaft it, it falls down under the crank. It's possible to fish it out with a magnet without splitting the case, but WAY easier to just not lose it the first time.

The 250 output shaft end is smaller, where the oil cooler line attaches, so you may have to drill it out slightly. Also, there is a spacer that goes on the opposite end of the shaft as the thrust washer (this one is closer to the oil line feed, inside in the side cover behind clutch.) You MAY need to use the 300 one, I'm not sure. I don't remember.

Basically, just remember to use a pipe after unbolting the output shaft from the case. You don't want any gears to fall or be misaligned.

http://3wheelerworldforums.com/showt...ighlight=300sx

[Jason T]

Glad my thread is Still being useful
After 6 years of use the bike is still running well
It doesn't get as much use as we would like, much like the rest of our bikes
Few pics of it in action, may have posted some of them before:

[86BigRedRider]

How hard is it to remove the 2 clutches?? Any special tools needed?? I have a friend that is going to remachine the 250es angledrive to match the TRX300's for installed length and the feed hole in the end. I'm just worried about that damn thurst washer falling!

[TheRealFatShady]

You don't need to machine it; I'm finishing mine up this week, also putting on a 4 valve head. But others have done just the output shaft swap without machining anything, just by bending the oil feed line to fit and drilling out the 250's oil feed hole to be the same size as the 300.

I believe it's a hollow tube if you cut the end off to make it the same length; this means you'd have to press in the little 'insert' (the cup shaped piece which actually has the hole the oil line goes through) and push it back. I assume there is some sort of lip in the way which prevents it from being pushed in further accidentally; if there is, then machining it will be a little bit harder.

I think it's like a 27mm or 28mm for those nuts.

All you need to do is make sure the oil line doesn't get hit by the primary gear that is attached to the rear of the clutch basket. You will need to enlarge that hole and push the feed line through it and bend it to get all the mounting holes to line up, but that's about it.

The clutches are really easy to change if you've done anything similar before. Basically it's two nuts, one of which is left hand threads (the centrifugal clutch I believe, the one closest to the front of the engine, not the tradition clutch setup with plates). You will need an impact gun and/or to seize the engine for at least the left hand one.

Also you need to take out 4 bolts and their springs on the other clutch. Just remember each nut has a washer behind it, they say on them which side faces out. And the nuts can/may already be staked.

EDIT - For the trust washer, just remember to take out the clutches first. You also want to carefully drill out the 250 output shaft oil hole before putting it in the engine, just use a bit that fits in the 300 one's hole. Use oil on the drill bit, try to get as much of the metal shavings out before installing.

And once the clutch and oil feed line are out, just get a pipe about the same size as the output shaft's end diameter (the end with the hole for oil in the middle) and use that as a guide/alignment tool/punch to get the shaft out. There's 3 bolts and 1 or 2 dowel pins holding it, but it's still kind of stiff to get started sliding. As the shaft is pushed out, it's immediately replaced by your pipe/tube/whatever you're using as a punch.

This way, all the gears and that very crucial washer ride on your guide pipe. When you replace the shaft with the new 250 one, it's the same thing but in reverse.

[86BigRedRider]

Ok that sounds pretty simple then. I should have those socket sizes at work. (I work for Honda fixing cars). Now for a different question...

Wheels~ What 12" rim will fit? I know it's a 4x110mm bolt pattern, but what is the side to side spacing? I know the original 9" rim is spaced 3 and 6". I plan to run some rear axle spacers to get the wheels out. And I want to replace all 3 wheels/tires. I'm liking the ITP Baja's.

[The Goat]

I wouldn't do bajacross on a big red personally...it'll beat you to death.

Have you seen the new sti black diamond? picked up a set day before yesterday. Just order the next size up as they run about 3/4 of an inch short

[85BigRed300]

Its a Process. I just got done with mine a couple months ago. You'll need to split the cases, so you might as well do a complete rebuild. Full gasket kit, piston rings. The only thing out of the ordinary is you will have to bend the oil line a little to fit in the output shaft. And drill out the end of the out put shaft to receive the oil line. Other than that its not bad. I went up a size on my main jet and up a notch on the needle
The electrical gets a little tricky. I ended up using a 300 cdi, spliced the wires for that according to the wiring diagrams, and the kill switch wire for the 300 cdi will need 12v power to run and open to kill. As opposed to Ground kill and open run on the 250 cdi. So i cut and spliced the wires to the kill switch and connected it to a 12v source and to the cdi. Note that now Your kill switch is reversed off=run run=kill. (I dont remember why i didnt use the 250 cdi, you may be able to but i had some issues and ended up doin it this way. Let me know if you have any more questions. I noticed more tourque for sure but not a night and day difference. Next step is the 355 big bore kit!!

[85BigRed300]

I know those guys are sayin you can just slide a pipe in place of the output shaft, and you can try it that way it would be alot easier, but i wouldn't.

[schneed]

Not sure what you mean by "beat you to death"?

And if I were to buy any ITP tires, I'd buy the Mayhems, now those are sweet (as least in the pic)!

Those Black Diamonds wouldn't work that well for the muddin we do (only 3/4" lugs?) I personally ride the Maxxis Mud Bugs (1.1875" lugs!), and luv 'em.