250sx stroker? has any done this?

[oldtrx]

im not 100% sure if they are or not... but if the bottom end of the sx and trx300's are the same then 450r transmission gears will fit. G H O S T on the highlifter forums has a trx300 4x6(2x4 with duals) web 40b cam, thumper racing 376 BBK, 400ex carb, and his will run 60^ mph and will lift the front end from a dead stop in 3rd gear.

[Tri-ZNate]

Whoa, dad! I thought you dropped off the face of the earth, bro. Good to see your textiles. And Yup, Nate KNOWS what he's talking about, too bad al the stuff from his SX build expired long ago, his was pretty cool...............

Yeah, Crasher knows better than I do though. Mine was simple bolt ons. He did engine mods. If you want more power, more snap, then put a 350x carb on it with a different exhaust. Really wakes them up.

[98rangerll]

ok that sounds like a idea bigger carb from the 350x and exhaust that might be just what would do the trick and alot less money thanks for more info guys

[TheRealFatShady]

im not 100% sure if they are or not... but if the bottom end of the sx and trx300's are the same then 450r transmission gears will fit. G H O S T on the highlifter forums has a trx300 4x6(2x4 with duals) web 40b cam, thumper racing 376 BBK, 400ex carb, and his will run 60^ mph and will lift the front end from a dead stop in 3rd gear.

I've seen that thread, it's like the inverse of a gear reduction.

If I ever get my SX converted into a FATCAT, maybe I'd look into that, but then it may be geared too high with the streetbike rear end on it. For now I'm more focused on getting everything ridable for playing in the snow; 350x, 480r, 300 4 valve big red/sx engine.

Today I finally got around to looking at the TRX300 engine and the output shaft. I worked with a new buddy, and got the 34mm OD (I believe) thrust washer back into place and got all the gears lined up on it. Had some restriction, but eventually it slid into place and every gear seems to be good to go now.

On a side note, I don't see a need to drill out the end 'cap' on the 250sx output shaft, the piece next to the clutch where the oil feed tube goes in.
It looks like it would be fine with the smaller hole (the stock TRX300 output shaft assembly had a much larger hole on the end) as oil will still get in, but less likely to 'spill' at the entry point. If I need to make it a minuscule amount bigger, I'm doing that while it's in the engine assembly, don't want to take it apart again to mess with it.

Next comes the 300ex or 250x 4 valve head assembly, will need a new gasket, reliefs cut in top of piston, and then maybe a 300ex or new head gasket.

It should be ready soon. Will likely put in my SX while the rest of the Big Red gets all the crap/rust/holes/bends etc fixed.

[oldtrx]

I've seen that thread, it's like the inverse of a gear reduction.




Next comes the 300ex or 250x 4 valve head assembly, will need a new gasket, reliefs cut in top of piston, and then maybe a 300ex or new head gasket.

inverse of a gear reduction would be using the 400/450 forman clutch basket with stock 300 primary gear (GR on 450/400 uses stock 300 clutch basket for 14% reduction, no modding required)


250x/300ex 4 valve heads are nice.... one problem... the motor rotates opposite direction so send your cam to WEBB and they can cut you a reverse cam .. if u have an account on HL PM gotmuddy he has done the 4valve swap i believe. also jamesrancher(the one who has has been cranking out 90% of the gear reductions on HL) he has built some HOT HOT HOT 300 motors recently..

food for thought

[TheRealFatShady]

Yep, I may have to talk to some of those guys again. One of them had some insane 500+cc build....stroked like 6mm or more, spacer places, custom studs, 4 valve head, big bore kit, etc....needs new rings every 6 months.

And I got the reverse grind cam from MHR on here. And had to make rocker arms, he offers it as a service.

[oldtrx]

seems like ya got it all figured out , good luck

[TheRealFatShady]

Sorry to clutter the thread, but do you know if the TRX300 engine has two dowel pins on the output shaft/where the 3 bolts hold it to the case?

I know I put the larger one on, but I just saw my old big red engine I stole the shaft from, and there's also a smaller dowel pin that I did NOT put in the 300. Don't think it will affect anything, do you?

EDIT - Yep, everything fell into place. It didn't at first, but constantly spinning the shaft/gears made it work. One I pushed it in further, it all seemed to be perfect.

Wow, it's not too hard to fish out that washer with a snake magnet. Can't imagine doing it without one!!!!

[98rangerll]

good info guys im learnign alot just also thinking about were to track down parts at to try some of this lol

[oldtrx]

as long as the shaft isnt getting into the seal before you snug the cover down i wouldnt worry about it, they are only there for alignment. just watch that is dosent move alot when tightening it down, shouldnt move about that much with the bolts started in it anyways,