250SX ideas that need a 2nd opinion

[Rajunrick]

Hello everyone. My work on my 85 250SX has slowed down greatly due to funds.
So at the moment all I can do to it is brainstorm. Here are my ideas so far, feel free to let me know what you think. So far I have ditched the stock frontend and have an 85-86 250R frontend on it now. The gas tank has holes in the bottom so I'm trying to decide if I want plastic or another decent metal tank. Found a place online that will make a metal tank but they want $400+ for it. I scrapped the stock swingarm and have an 85 TRX250 swingarm to go in its place. I know I'll need to fab the shock mount on it. My biggest brain teaser is this, do I build the 250, swap it in for a 300 and change the angle drive and wiring, or do I dare try and see if an 86 TRX350 4x4 motor will fit? On the 350 I haven't made any measurments yet, but it does look like it would fit. Of course I would have to change the angle drive, the leftside crankcase cover (was thinking that the 300 or 350X cover would do the trick), and the wiring. Already have a 350X carb on the 250 now. The advantage of the 350 would be like having a shaft driven 350X. From what I've researched so far, the 350 and 350X are in fact the same motor. The possibility is in front of me, just have to decide what to do. The guy I'm dealing with has a 300 motor and wiring and also has the 350 and wiring. As soon as my money is right, I'll take my spare 250 motor and see if it would fit in the 350 frame. So let me know what you think.

[Name Brand]

I'm curios what you come up with for the lower shock mount on the swingarm.

I'm pretty sure the rear brake was upgraded (better sealed) on the '86 models.

Phew, don't know what to tell you on the engine choices! I resigned myself to the stock 250 engine till it dies; then I'll put in a 300.

[The Goat]

I personally think that even if you did manage to get that 350d engine in there, your gearbox would go CRUNCH...

300 route with a 385 big bore....done.

[Dirtcrasher]

I've never seen a rear diff fail from broken teeth....

And the tranny the SX runs has the same size gears as the 350X.

I think your merely limited to how it bolts up and lines up.

To me, the SX doesn't need any more mods than what you can do to it in stock form. The top end speed and suspension are limitedand thats what mademe move onto the 200 and 350X.

I still love my SX but put 20 hours on it in 3 years versus hundreds on the others.......

[The Goat]

I've never seen a rear diff fail from broken teeth....

come on down to the thick mud of the bayou land...300 hondas running vamps, and big reds running AG tires...

I've only seen those two types go crunch...but both have heavier gearing than the 250sx don't they?

but we're talking upping the hp from the 250sx to the 27 crank hp of the 350...that's a fair jump...

I wouldn't trust the rear in the thick stuff....especially if I was running oversized tires.

catch one good tree root when spinning the tires pegged in second...bam.