Will a Bigger motor fit in an SX?

[Tri-ZNate]

I have some time on my hands this winter and was thinking that since i have so many SXs I would trick one out. My first plan is to put a bigger motor in it if possible. I was thinking like a rancher, forman or even a diff make like a 350 big bear. Has this been tried by anyone?

[bigredhead]

If you're gonna do up an SX.. make sure to work in Reverse and elec start !

Need to stay with the theme !

just more power !!

argh arghharrrgh.

[Tri-ZNate]

Hell Yeah! Tool man! Gonna Make my baby purrrrrr.

[Dirtcrasher]

I have some time on my hands this winter and was thinking that since i have so many SXs I would trick one out. My first plan is to put a bigger motor in it if possible. I was thinking like a rancher, forman or even a diff make like a 350 big bear. Has this been tried by anyone?

If you want to trick one out, figure out a rear suspension improvement. The last thing the stock SX needs is a bigger, faster, heavier motor to try and ride without being tossed off. That rear pogo stick should be priority number one. I have been promising alot of guys that I would come up with something for the SX and I am still working on it. I'm not just gonna hack anything on there, I want it to look and work great.

[Tri-ZNate]

Well if the motor required a diff rear then I could try to make mounts so the shocks would work. The mounts im speaking of go at the top of the shock.

[03 ORANGE SHEE]

ever try the 86 trx 3504x4??, or a dirrect bolt in, an 88-99 trx 300 4x4?? same cases, different stroke

[Tri-ZNate]

Im making a list from what has been said in here and what I think. Any Adiitions? and remember I'd like to know what higher cc motor i can put in


So far.....
Things that need to be done to trick out my SX:

Different (refered to as diff) rear suspension
Smaller tires in back
New plastics all around (200x up front and 350x rear)
New motor
350x headlights
Twist throttle
New exhaust (probably cobra megaphone)
Bigger carburetor
K&N or UNI air filter


Any other suggestions?

[Tri-ZNate]

ever try the 86 trx 3504x4??, or a dirrect bolt in, an 88-99 trx 300 4x4?? same cases, different stroke


So far I havent tried anything yet. Also what makes the wheels up front turn in 4x4, isnt there another drive shaft that comes out of the motor for the front?

[hrc85250r]

[QUOTE=250sxwheeliepop]
Different (refered to as diff) rear suspension
QUOTE]

He means differential rear suspension, not different... :rolleyes:

[Tri-ZNate]

I dont think I mean differential. If I have time im gonna try to make a different rear suspention


ADDITION: diff is the way I write different in short hand

[RichinMO]

Might as well get a 400ex jug and sleeve it out to 440, that should bolt up to your lower end. Hopefully you can get the 2 headpipes around the downtube. Do that and then upgrade the suspension front and back. Then worry about the piddly stuff-(headlights, stickers, etc.)

[Yamahammer490]

Well if the motor required a diff rear then I could try to make mounts so the shocks would work. The mounts im speaking of go at the top of the shock.


That picture looks like the quad has independent rear suspension. I've always wondered how a trike would work with IRS.

My guess is that it would either be real tippy and handle like crap OR it would give you a little leaning ability and handle more like a bike. Sorry to get too far off the track but the picture sparked my interest.

Aside from that, I like the SX with the wide front tire so please don't put a "X" front end on it. :D

[Wickedfinger]

Personally, for all the work it would require to get a TRX350 motor or even a TRX300 mill in there you really need to ask yourself if its worth it. I can guarantee the 250SX motor probably has more ponies stock than the 300 or maybe even the 350. Just because they have more cc's dosent mean they put out the kind of power a sport bike would need. Even though the SX motor is basically the 250ES utility motor, its tuned differently. My advice would be to work your motor - first thing I would do is look for an aftermarket exhaust, more aggressive cam and drop a medium compression or hi-comp Wiseco in it. You will see far better results.

[Tri-Z Pilot]

There use to be a 300 kit, I think four stroke tech made it (fst racing).
I'd put a 200x front end on, probably dont want to go too big on a carb, as you will loose bottom end the bigger you go, I hear cobra's are junk, might want to see if they made a supertrapp or DG system for it. Another upgrade is an 87 rear end. I hear they spice up the earlier models. Your going to want to watch how you mod the suspension, the shaft is to one side, and when you start playing around with independant units you'll have to measure pinion angles so you dont go binding your drivetrain.

[smokinp]

why not just leave the 250sx alone and buy like a 200x or 350x.sounds like you need one...

[BigGreenMachine]

I agreed with Wickedfinger, mod your stock engine with a cam, pipe and piston and you will see far better results. I'm sure a stock SX vs a stock TRX300 would see the SX having the faster acceleration and top speed. Try mods like wheel spacers and aftermarket fork springs. As for the rear shock why not get it sent off to Works for a rebuild, heavier duty spring and have them set it up for your weight.

Money spent to buy and install a 300 motor only to see a lackluster result is just not worth it IMO.

[250sxer]

There use to be a 300 kit, I think four stroke tech made it (fst racing).
I'd put a 200x front end on, probably dont want to go too big on a carb, as you will loose bottom end the bigger you go, I hear cobra's are junk, might want to see if they made a supertrapp or DG system for it. Another upgrade is an 87 rear end. I hear they spice up the earlier models. Your going to want to watch how you mod the suspension, the shaft is to one side, and when you start playing around with independant units you'll have to measure pinion angles so you dont go binding your drivetrain.

I have a '85 250sx. It's fresh. All I did was put a uni-filter and Cobra Megaphone exhaust. I was told by someone else on this site to use the stock main jet from a 350x carb (138 I think) and put 20" tires on it. I didnt do it. I saw good results with just the $120 I put in it. I have 22" Bear Claws and that beast just won't get stuck and tops at 64 mph. As far as the exhaust, Cobra Megaphone is the only exhaust they make for the 250sx, trust me I checked everywhere. But the other guy was right about the power of the 300 and 350, your 250sx is geared differently and the TRX motors will not be as quick or as fast. By the way, I am looking for a 6 pack rack for my '85 350x.....can anyone help????

[Tri-ZNate]

Personally, for all the work it would require to get a TRX350 motor or even a TRX300 mill in there you really need to ask yourself if its worth it. I can guarantee the 250SX motor probably has more ponies stock than the 300 or maybe even the 350. Just because they have more cc's dosent mean they put out the kind of power a sport bike would need. Even though the SX motor is basically the 250ES utility motor, its tuned differently. My advice would be to work your motor - first thing I would do is look for an aftermarket exhaust, more aggressive cam and drop a medium compression or hi-comp Wiseco in it. You will see far better results.


From what ive heard from the forums though all that will do will make it a little peppier. Im not quite sure what i want the motor to give me. I guess I want to have a little more speed for when I drag race my dad and to make my friend's trail blazer bow down to me. I suppose that would be the smarter move just doing mods to the original motor then to put a whole diferent one in there.


Might as well get a 400ex jug and sleeve it out to 440, that should bolt up to your lower end. Hopefully you can get the 2 headpipes around the downtube. Do that and then upgrade the suspension front and back. Then worry about the piddly stuff-(headlights, stickers, etc.)

What cams can I put in, and what advantages would a 400ex jug give me?

[Tri-ZNate]

Oh also If anything ill put a 350x front end on. AT the moment im just looking to put a 200x front fender on and a 350x rear fender.

[BigGreenMachine]

I'm pretty sure when I say a 400EX jug won't bolt onto an SX bottom end. Trust me on that one.

The rearend on an SX is the limiting factor to top speed. All you can really change now is how quickly it accelerates by modding the motor. A TRX rearend may bolt in but again I don't know if its geared higher than the SX.

[yater]

That picture looks like the quad has independent rear suspension. I've always wondered how a trike would work with IRS.

My guess is that it would either be real tippy and handle like crap OR it would give you a little leaning ability and handle more like a bike. Sorry to get too far off the track but the picture sparked my interest.

Aside from that, I like the SX with the wide front tire so please don't put a "X" front end on it. :D


An SX with IRS would be a deathtrap! The only thing that keeps a trike upright is it's ability to slide through corners. Without a solid rear axle, the trike wouldn't slide worth a damn

[Tri-Z Pilot]

I'm pretty sure when I say a 400EX jug won't bolt onto an SX bottom end. Trust me on that one.

The rearend on an SX is the limiting factor to top speed. All you can really change now is how quickly it accelerates by modding the motor. A TRX rearend may bolt in but again I don't know if its geared higher than the SX.
Yeah, I'm pretty sure I would have read on here if it was possible to just bolt on a 400ex jug, all sxer's would be doing it.
I think that the trx rearend is identical to the sx, but I'm not positive

[Wickedfinger]

Yeah, I'm pretty sure I would have read on here if it was possible to just bolt on a 400ex jug, all sxer's would be doing it. In theory, anythings possible - but it would be next to impossible to get a four-valve jug to work on a bottom end made for a two valve set up, especially when the 400EX's is bolted on with 6 studs and the SX only has 4.

[Tri-ZNate]

Yeah the trx rear is compatable but its just not worth it. Ill just make mods to the engine I have now then when I get like a 350x or R I'll play with it a little more. Thanks everyone for your advice and info

[JLurch58]

I have a 85 sx with a 200x front end. Motor runs great but the axle is missing. It has a Cobra exhast and new plastics. Its for sale in the Rimersburg Pa area. I may even let you take my R for a ride, MAYBE. LOL

[BIG_RED-ICULOUS]

Hi guys, I`m new here, but not around honda trikes. I`ve personaly built two big red with trx 300 motors in them. they work awsome. lots of useable low end grunt. the power reminds me of a foreman 400 motor. Just thought i could help!

tyson

[Lomax]

Here's my theroy on what I would do

Front end from a 350X or 250R
Rear shock thats slightly taller but not too much due to driveline angle
Wheel spacer to get a better stance
Good Exhaust
250X TRX carb (works good)
Now on the engine this is something I have always wanted to try
There used to be these bolt on 300 kits (yes for an ES and SX). They consited of a new cyclinder and piston and gaskets. This woudl give you a now 300SX if you can find one of these. Now here's the part that would be awsome. I have a 97 TRX300 crankshaft here, Lets suppose it would fit, stock CC difference is 246 vs 282, thats a difference of 36cc's of engine, mate that up (if it would work) with the aftermarket 300 cyclinder. 336 torque monster... Ok im done.....