250sx racer

[191145guy]

Has anyone ever seen or heard of someone racing a Honda 250sx

[Joseph Farrow]

No one did back in the day.....maybe in modern times.

[fabiodriven]

You could race it just for fun. All the races at Trikefest are just for fun and there might be other events where you could get it into a certain class, again, just for fun. They're obviously not made for MX. The swing arm can get bent from big jumps, the SX is a tank.

The SX would be far more suited to a hare scramble or enduro racing.

[Gabriel]

Aside from the weight and girth of the machine, not being able to change your final drive ratio to suit the track would be a major hindrance.
Nothing stopping you from trying it though.....Give 'em hell!

[oldskool83]

its a trail racer. I had two of them, fun machines.

[ps2fixer]

I've raced my cousin's TRX250x and he barely beat me on a gravel road, but that's stock to stock and who knows which machine has more engine wear lol.

Are you looking to build a race machine, and what kind of racing?

Gear ratio can be modified a little, 250es transmission gears interchange to give lower gearing, and the 250es rear diff changes to give lower gearing. Not sure if there's anything that interchanges to give higher gearing though. Tire size of course effects gearing too.

I suspect the go to mod would be a first gen (83-85) ATC200X front end swap which is lighter and has a narrow tire (also lighter) and has disk brakes (lighter again and can be upgraded I'm sure). The ~86 TRX250 utility 2wd quad swing arm is nearly a bolt on interchange for +3in swing arm. I think the only thing you have to do is weld up a new shock mount. There's atleast one 350cc big red modded engine out there, I'm pretty sure a TRX350D top end or a ATC350X top end was used. It's 4 valve instead of 2 besides being larger displacement, so better for high rpm max power. Besides weight reduction and such, I'm not sure of any other performance mods to do besides like carb swaps, exhaust upgrade etc. It would be neat to see a 250sx race machine, I think the sx could be fast, but the suspension needs to be reworked (too stiff) and shaft drive is an automatic like 20% power loss vs chain drive. I suspect if the machine was purely race only, the primary clutch could be replaced with a solid gear setup and use the clutching on the shifter for taking off and changing gears, not sure how the kick start would work, might have to be electric start only with that mod (jump it at the pits or w\e). If you went super extreme, I think you could also pull the reverse gears out for weight savings, but I'd think having reverse would be quite handy to have and it's not saving much.

Anyway, the go to race machine was the ATC250R, the ATC350x can do alright for a 4 stroke and I've heard people hopping up the 200x can make it quite fast too (lighter machine than the 350x). Of course all are chain drive.

[191145guy]

I don't race I was just wondering if any body had a modded one for racing

[Tfields87]

I was wondering the same thing I love the look of the 2nd and 3rd gen 250r with low profile fenders but there's no options for those plastics on a 250sx I did put a 10x5 front wheel and 20s with 2 inch spacers on the rear and it made the bike alot more stable in the corners and light for wheelies I really want a set of aluminum rear wheels and after purchasing the steel front I wish I would have shelled out the extra $20 for the aluminum wheel I'll try to post pics

[Tfields87]

257208here is my 250sx

[ps2fixer]

Your 20in tires probably did a lot more for the wheelies than the weight. That's about 10% lower gearing which can make quite a large difference on an ATV.

I tried riding my sx with wheel spacers (1.5in per side, 3in overall), and I hated how it effected the handling, it didn't turn as well and such. yea it was less "tippy" but it's the nature of the beast, give it more gas and the back end goes back flat besides really leaning into the turns, also called body English. Look at the 80's era atv racing videos to get an idea. This tip is more or less 250cc or larger though, maybe the 200x has enough power, but like a 200es is too heavy and low power to really ride hard like that to get the back end to go flat with more gas.

My cousin's 250sx has a 250es rear end in it, and his became a wheelie monster with the minor difference in gearing. Both machines are 85's and both ran about the same and both were on 22's (stock size tires).

[Tfields87]

Yes sir tippy is what I was referring and for me the spacers made a better ride because I'm a little fat and out of shape to be doing all that body English you are speaking of

[350for350]

Personally, I like the 1.5" spacers on my 85 250SX. I have noticed that it doesn't turn as sharp as it should, but reverse still works too. I wouldn't go back to stock width.257213

[Tfields87]

So I don't know if I'm doing this right but t herei s a link to to a thread on big bore and cam kits for big reds and 250sx it really has me intrigued. ps2fixer is the trx250 swing arm a +3 stretch or width?

http://www.3wheelerworld.com/showthread.php/173824-The-all-new-Big-Red-250es-250sx-350cc-big-bore-kits-are-in-stock?highlight=big+bore+250ES

[ps2fixer]

Makes sense, your riding style is just different from mine. I ride pretty hard and slide though a lot of corners, the tight turning I use all the time in wooded trails. I was kind of thinking a lot of people in 3 wheelers are also older than me so bad backs etc could be a good reason to run spacers.

The TRX250 swing arm is +3in in length. I didn't measure the width, I suspect if you used the left side spacer piece from an SX you could run an SX axle, if I recall correctly, that's how we fit a 250es rear axle in my cousin's 250sx. His SX's splines on the axle were worn out, and I didn't check the rear diff, but I assumed it was also heavily worn so opted to replace both. I think it was an 86 250es rear end too so the swing arm part was the other style since our machines are 85's. The swing arm bolts to the frame the same though. I didn't personally test fit the trx250 swing arm on an SX, but I read it was possible, and I measured the length to see what the difference was since it wasn't mentioned. Somewhere I have that swing arm yet, not sure if I'll ever use it, or just sell it, If I recall correctly it was from an 86 trx250. My cousin seems like he doesn't ride his SX any more and he owes me some money, so maybe I'll end up with his machine. It's a little bit rigged up and such, so it could be an interesting machine to do some mods to and test ideas out on, and make kind of a "racer" machine, but with lights and minus the expensive engine work.

For the big bore kit, race wise, I think you can mod the SX engine to accept a TRX350D or ATC350x cylinder + head + piston, but I'm not sure if it would have the right stroke, might have to use the TRX350D crank for that. The TRX350D is basically a 250es/sx bottom end with an atc350x top end, maybe just swapping the whole engine over would be possible. Kind of wish I had a roller frame to test that theory in... well I do have a parts 250es, but it's missing some rear end parts. It's engine was a smoker and didn't shift right (thinking bent shift fork), so maybe an engine swap will be possible. The TRX350D I have is basically no fenders because they are so sun rotted, and something either the front swing arm or the frame is bent so on flat ground only 3 tires touch. Besides that, the TRX350D lives up to what people describe driving them as.. a "tank", they turn like crap, super heavy, but seems to be able to pull a lot. My engine also has a slight knock to it that I have to figure out, low rpm it's like a bottom end knock like the rod, but higher rpm it goes away completely, maybe weak oil pump or some oil pathways are partly blocked or something. I wouldn't have anything happening on this idea for a while, too cold right now and glare ice everywhere.

Anyway, if you wanted some measurements, I could probably get them off the TRX250 swing arm I have. I don't recall for sure if the axle is installed yet or not, but the swing arm should be in the shed I'm thinking of. There's a fair chance the TRX rear axle might be narrower than the SX, but an axle swap should be possible. The diff is also one of the few that can work with the 250ES/SX if I recall correctly (based mainly on photo and them looking the same atleast). I think there was 3 or 4 machines that were the same layout/look.

[Tri-Z 250]

Just go as is...gate up at a local harescramble. Your machine is already Race, other than bars if stock. Tricking out the Stock Spring rates revalve and oil rates will improve performance on time, over motor mods. A better exhaust with a simple rejet of the carb always the cheapest in power gains. In the woods it's the rider at the end of the day, the SX has proven hours of mud time left in it. Go have fun on it ! Back in 2006 or so a guy came to run SmithRd MX on a BigRed. He just set his own pace and had a blast doing it.

[swampthang]

Hot Rod 250sx... the idea has pasted my mind a couple times. Its fun to build a machine that's kind of a sleeper. Yes there are lots of ways to hop one up motor wise but in the end your left with a heavy machine with limited handling and an empty wallet. One other mod for speed that hasn't been mentioned is changing the primary drive gears. guys take the primary drive gears from 250es/sx and 300 fourtrax and put them in foreman 400/450 for a 14.5% gear reduction. Havent heard of anyone trying it but if you could fit foreman 400/450 primary drive gears in a 250es/sx case then you would gain 14.5% higher gearing for more top speed.

[schlepp29]

That would be cool! A little bit more speed for the back roads would really nice.

[ps2fixer]

Hot Rod 250sx... the idea has pasted my mind a couple times. Its fun to build a machine that's kind of a sleeper. Yes there are lots of ways to hop one up motor wise but in the end your left with a heavy machine with limited handling and an empty wallet. One other mod for speed that hasn't been mentioned is changing the primary drive gears. guys take the primary drive gears from 250es/sx and 300 fourtrax and put them in foreman 400/450 for a 14.5% gear reduction. Havent heard of anyone trying it but if you could fit foreman 400/450 primary drive gears in a 250es/sx case then you would gain 14.5% higher gearing for more top speed.

Generally most people want lower gearing for racing. My 250SX topped out at 52mph based on a Rincon's speedometer on a dirt road @ ~700ft elevation.

A cheaper way to get about the same gearing difference is to throw 25in tires on instead of 22's. The machine looks a bit funny but they fit fine. I'm not sure if the 250sx in stock form has enough guts to use the higher gearing to actually go faster and overcome the wind resistance, seems like it didn't fully rev out when I tried the top speed run.


Another option for lower gearing is to either swap the transmission gears from a 250es, or swap the whole engine. The 250sx rear end + transmission is setup for 22in tires, and the 250es is for 25in tires, from what I've read the final gear ratio (engine rpm vs tire travel speed) is the same on both.

Also when I was doing that top speed run, my cousin's 87 TRX250X performed about the same as the 250sx. It wasn't my machine, but it seemed to run well. I can't recall who was faster, but it was close for top seed.

Quick story, my uncle put 14in rimmed car tires (around 25in or 26in tall probably) on his 650 Rincon to travel around 20 miles to state land, then road on the state land trails with the car tires and did fairly well. Only thing he said was a problem was mud because the tires had horrible tread for mud. Pretty much anyone could do the same thing, you just need to get a set of ATV rims that are 14in and throw car tires on them (used or cheap works fine). The ATV is a lot lighter than a car, so in theory the tires should last a long time. It looks a bit funny because they are so skinny, but it is more ideal for road traveling if that's something you do a lot. It should give a little more top end from less wind resistance (skinnier tires), and less rolling resistance assuming you're top speed isn't rpm based. Just don't try to blow up your machine by trying to go 60mph at red line rpm for 20 miles lol.

[swampthang]

Depending on what type of racing you are doing most people go to a smaller tire like a 18 or 20. I had a sx that had 18s on it when I bought it and it was painfully slow 1st and 2nd gear was nearly unusable as you was only in them for a second, 3rd-5th it pulled good as you actually had time to let the motor rev and use its power. Top speed was terrible never tested it but id guess 30-35 at high rpm and you wouldn't want to run it at that rpm for long.