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Thread: 250sx racer

  1. #1
    Join Date
    Oct 2018
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    Tn/Portland
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    15

    250sx racer

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

  2. #2
    Join Date
    May 2013
    Location
    Brownsville, Tn.
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    1,102
    No one did back in the day.....maybe in modern times.
    * 1978 ATC 90/180 Pauter PJ1 / Springer "Team BAPP" Bike *

    * 1980 ATC 110/180 "Danny's Machine Works" 3D Sprint Dune Bike *

    * Nicholson 500 Race Bike *

    * HPATC Yamaha RD350 "Big Moe" Trike *

  3. #3
    fabiodriven's Avatar
    fabiodriven is offline Aspiring romance novel cover model, and the Official 3WW slayer of thieves and swindlers. Catch me if you can
    Join Date
    Jun 2008
    Location
    East Bridgewater, MA
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    9,956
    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.
    85 Tri-Zinger 60
    85 ATC250SX
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    87 ATC250SX
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    84 ATC 480R

  4. #4
    Join Date
    Jul 2018
    Location
    TN
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    584
    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!
    Amateur Resurrectionist

  5. #5
    Join Date
    Jul 2005
    Location
    Manheim PA 17545
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    4,824
    its a trail racer. I had two of them, fun machines.
    2005 KFX700
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    Coal Country Rider

  6. #6
    Join Date
    Apr 2012
    Location
    MI, USA
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    2,689
    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.

  7. #7
    Join Date
    Oct 2018
    Location
    Tn/Portland
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    15
    I don't race I was just wondering if any body had a modded one for racing

  8. #8
    Join Date
    Jan 2019
    Location
    Cleveland tx
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    15
    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

  9. #9
    Join Date
    Jan 2019
    Location
    Cleveland tx
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    15
    Click image for larger version. 

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ID:	257208here is my 250sx

  10. #10
    Join Date
    Apr 2012
    Location
    MI, USA
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    2,689
    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).

  11. #11
    Join Date
    Jan 2019
    Location
    Cleveland tx
    --
    15
    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

  12. #12
    Join Date
    Apr 2014
    Location
    Edmond, KS
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    1,484
    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.Click image for larger version. 

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  13. #13
    Join Date
    Jan 2019
    Location
    Cleveland tx
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    15
    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/showthr...big+bore+250ES

  14. #14
    Join Date
    Apr 2012
    Location
    MI, USA
    --
    2,689
    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.

  15. #15
    Join Date
    May 2006
    Location
    N.E. Ohio
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    1,810
    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.

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