250sx stroker? has any done this?

[98rangerll]

i bought 2 85 honda 250sx for 300 bucks one needed the kick starter spring installed and cdi box is what i was told im working it now hopfully will have it running in the next few days the second i was told that the guy he got it from put 400ex valves in it so i got another head and am planning on rebuilding it but im thinkin if i have it tore down that far i might try to make a stroker out of it has any one done this if so were can i get the parts to do this or send away to get it done thanks

[TheRealFatShady]

Maybe you can bolt in a trx300 crank.

[Dirtcrasher]

By the time you get stroked, and a piston/cam/valve springs and an exhaust to compliment it you'll be 1000$ poorer and with a trike that will get to 50MPH a bit faster........

[98rangerll]

well dirtcrasher i talked to a machine shop in nevada that said they might be able to do the stroker protion for 450-500 and a cam and spings is gonna run bout 150-200 or so i think im also thinkin bout boring it 20 over at the same time witch piston rings and boring is gonna be bout 200-250 more so your 1000 buck estimate is pretty acurate from what i have found out looking around and piecing stuff togeather from thread to thread the pipe im not even sure who makes them for it is the aditional power and exceleration gonna be worth the money ??? and if you know of a place you could recomend to get any of the work done please help me out cause im looking at a big bill to complete all this and i want it done right also if im already into it as far as all that does it make sence to port and polish it while im in there?

[Xpress]

A 250SX is not going to get a whole lot better. It is what it is, and it's a good sport/utility trike.

FYI, complete sentences help out ;)

[TheRealFatShady]

It seems like a LOT of cash to spend on a 250sx engine. I've seen Dirtcrashers SX, never rode it. I think he has about $600 into the top end alone on it, 350x carb, 200x front end?, and it's only a little better than a stock sx he told me.

I know some guys use the TRX300 engine and mod the hell out of those things. For $1000, you can probably buy a full engine/wiring, big bore kit, cam, clutch, etc. Or just use that crank in the 250sx, it's the same bore, stroke is longer.

I have a 4 valve head I am planning to put on mine....hoping to get to trying to put it on this weekend, depending on what happens tomorrow in court. If that works, it may be a very significant benefit, and cheaper.. But machining work is of course required.

Highlifter.com - check their forums for engine mods.

[98rangerll]

TheRealFatShadyok So if i understand you right then a trx 300 crank will fit in my 250sx cases and work for a stroker but if im looking for more power i would be better off just getting a trx 300 and bolting it in with some mods. i appreciate your imput on this its a good idea ill try and do some resurch on it. i also apreciate the info about Dirtcrashers sx and how it realy hadnt made much of a difference with what he has done. let me know how putting your 4 valve head on goes and how it works when its done sounds like a fun project i hope all goes well for you and again thanks for the info and links.

Xpress i also appreciate your oppinion im gettng alot of good imput and ideas and possible alternative ideas to moding my engine and goin with other possibilities i do also appolagise for my spelling and grammer i never have been very good with it and in the army i realy didnt need it so im pretty bad eith it but im workin on getting it a bit better again thanks for your imput also

[Chazz of Blades]

For $1000 you could just start looking for an atc thats MADE to be fast, instead of spending a wad on one thats not, and making it a bit faster. Look for a 200x if you can.

[TheRealFatShady]

Yes, I believe the cranks *may* interchange, I read up on it but then found a TRX300 2wd engine,. 1988-2000, must be the two wheel drive model.

You need the output shaft from the 250es/sx engine, there's some threads on the search.

Just know that the SX will not do any larger jumps, a 350x or 250r is best for that. It will still give you more power with the TRX engine, and you can always swap the differential for a big red 250es one for lower gearing/torque if you wanted.

[98rangerll]

i bought 2 of the 250sx for 300 bucks im putting togeather the best i can from the 2 i might sell the second one and get a 200x or even a 350x im still at the resurch stage on this i have never had a 3 wheeler so its all new to me i am trying to figure out what makes sence and make sure i have a strong running machine and get the other running and go from there i might even just go for a stock build on these and sell one and then get another one that goes faster later im just trying to make descition with some info so i dont do somthing to crazy lol

Chazz of Blades thanks for the advice

[Chazz of Blades]

I have a 250es, 200es, and soon to be a 200x. Theres really not a whole lot you can do to your workhorses to make them keep up with a racer, unless you send about the money to buy a racer down the pit for it. Read my thread about my quest for a 200x, They are AAAALLLL worth it, and more common and cheaper than a bigger 350x, which I would not go with if I was a beginner, same with the 250r and Tri-Z. I prefer a 200x for what it is, and I know I cant do hardly anything to my BRs to match it cheaply. But great steal on the SX though, I wouldnt mind having one myself, but I've never saw one localy.

[Dirtcrasher]

If that crank fits, thats an easy solution with a spacer plate or a piston with a higher pin.....

[Tri-ZNate]

By the time you get stroked, and a piston/cam/valve springs and an exhaust to compliment it you'll be 1000$ poorer and with a trike that will get to 50MPH a bit faster........

Like dirt said, it can only be so much at 50mph. Fix up the SX for trail riding and pickup a cheap 2 stroke to pour money into. Been there, done that, and IMO an SX isnt worth pouring money into to make it "fast"

[the great gazoo]

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...............

[98rangerll]

ok guys thanks for all the imput i think im goin for a basic top end rebuild to take care of the smoking engine and get a little better compression but other than that atleast on the sx im just gonna get em goin so to speak and clean up the frame and diff ad call it good might end up selling one later to get a x though im kinda afraid to get a r last time i rode a 2 stroke i ended up in a barbed wire fence lol

[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,