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Thread: New/old Guy, old Question

  1. #1
    Join Date
    Nov 2019
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    Florida
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    New/old Guy, old Question

    Hello First post,
    I searched, a lot before asking this question, found a lot of information but not exactly what I was looking for.
    I have a 1985 250sx, I know its not the 250r or even they 350x but I always liked the look of the flat track bikes.
    I really like the TT street type tires. I read lot of concerns with "bell" wheels clearing rear brake drum, I read lot about 350x front ends and disc brakes.

    So what I am looking to do is upgrade to 20/10x10 rear tires with TT/flat track tread pattern
    and a 10x5 with a 22x7x10 front kenda with the slot front tire. both front and rear Douglas aluminum wheels. 4/110 pattern

    I also saw where some guys rotate the front forks and move the axle to the front of the fork. does this help?
    If possible, what offset would widen the rear without spacers? Possibly use a wider rim with less backspacing?
    How do the TT tires ride? do the slide well? I ride on hardpack trails and roads, no mudding, no rock crawling, no big hills.
    I am sure a pair of holeshots would hook better, but I am more into light trail and dirt road riding, donuts, wheelies type stuff. I figure the 20" tires would lower the bike a bit, be easier to spin along with the lighter wheels, the 22 front would add some rearward rake.

    I also know the sx is not intended for this type of flat tracking. but I wanted auto clutch and reverse. So the 250sx was my pic.

    Sorry, seems I am not allowed to post pictures yet.

    Thanks in advance
    MrC.
    Last edited by MrConcdid; 11-25-2019 at 03:46 PM.

  2. #2
    Join Date
    Nov 2019
    Location
    Florida
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    nothing, Really?

    116 views, not a single response.
    The site wont let me post pictures, I was able to in my intro but not here. idk

    MrC.

  3. #3
    Join Date
    Apr 2012
    Location
    MI, USA
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    3,489
    I don't know exact answers, but I've own two 250sx's so for the back spacing on the rim, just guessing but it looks to be about 2in in from the inner face of the rim. I think the offset is based on center of rim though so like -2in if it's a 8in wide rim. 10in should clear just fine, the OEM is 8in with a big offset outward. The ATC250ES brother to the 250sx uses 9in rims and if I remember right a little less offset. I guess long story short, you want the rims pushing out as much as possible, center offset rims has to clear the whole drum. Bolt pattern from memory is 4x110mm.

    If you want more ability to spin tires, you could look at engine mods. I know the early TRX300 is used to source parts sometimes, I think the engine was a near direct bolt in swap after swapping output shafts to make it have the right offset for the shaft drive. If you want a longer swing arm, look up the first model of (something like 1985-1987) TRX250 (2wd utility quad), it's swing arm is about +3in longer than the 250sx one and should be a bolt in interchange + welding in a new shock mount. I don't recall if the rear axle was wider or not.

    Not sure if pushing the front tire out further would help for your goals or not, I can't remember the riding characteristics that it effects. A lot of people like to swap to the ATC200X front end but the 350x and 250r are options too, I think the forks just need to sit down the tubes a bit farther to stay level.

    If you don't mind the challenge, in theory you could run wider hubs but you'd need one that is larger than the axle tube bearing size and turn it down so the bearings are still used and sealed. The axle design requires the axle not to move side to side, so sadly no way around this unless you want to do some taboo mods like welding the ring gear spine to the axle but I think that makes the 85 machine impossible to remove the rear axle, the 86 the axle tubing is removable if I recall correctly and same thing with the TRX axle/swing arm.

    If you want lower gearing, another thing you could do is swap in an ATC250ES diff as a whole unit. It's not a huge gear reduction, but it's enough to notice it. My cousin's 250sx had a bad axle so we swapped it to the 250es diff/axle and his machine is a wheelie monster more so than stock. If you want even lower gearing w\o extreme mods, swap the 250sx engine out for a 250es, the transmission gearing is the main difference between them.

    You can get into extreme mods for gear reduction like changing the primary gears out from a TRX model which requires welding and probably riveting/bolting/welding the old clutch basket to the new gear.

    I ride a 350x as my main go to because of the power characteristics it has, pretty much what you described, the 250sx is my 2nd pick. The only thing I long for is the 250sx to have the power of a 350cc. Some day I hope to mess around and get a TRX350D engine swapped into a 250sx frame. I think the mounts are completely different, so not an easy swap.

    I recall people swapping cylinders and pistons out with a machine, like the TRX300 utility machine to make the 250sx 300cc. I think you can swap the cylinder/ top end over from the TRX350D if you bore out the 250sx crank case centers to accept the larger piston. Probably more to it than just that but I know something similar was done with a 250es.


    Not sure what restrictions there are for images, but I suspect they might be 60 days + 10 posts or maybe just an age related restriction. You get the error that says you don't have permission right?

    Ironically I wanted to do something similar with the 250sx machine that I swap the 350 engine into, lighter rims, 200x/350x front end and maybe strip the lighting and charging system out to reduce weight. Longer swing arm swap too. Basically make a shaft drive version of the 350x. The 250sx is about 18hp, and TRX350D is 24.5hp. To compare, the 350x calcs to about 26.6hp. I think the hp specs are from the era where they tested at the crank, but I could be wrong. Shaft drive naturally looses more power vs chain drive and is heavier spinning mass and suspension but the low maintenance and high resistance to issues is nice =).


    Hopefully this atleast helps get you pointed in the right direction for further research/searching.

  4. #4
    Join Date
    Apr 2011
    Location
    Mexico
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    7,911
    Thereís a good number of photos of Mickey Dunlopís 200 based trikes on here and the Internet in general. All the forks Iíve seen are trailing. Contacting him directly might be a good option to point your project in the right direction.

  5. #5
    Join Date
    Nov 2019
    Location
    Florida
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    Thank you both for responding and going to such detail.
    Yes, I can not post pictures on any thread other than my profile. No message per say, the manage attachments button is missing.

    Yes, it seems a blend of 250sx and 350x would have been the perfect bike.
    Power, handling, auto clutch, reverse.

    I have bought rebuilt and sold many many atv, I only work with Hondas. This is my first atc, other than growing up with them in the 80s.
    I like the look of the 10inch dwt wheels, I wondering about a larger front say a 24 or 26 and a shorter 20 inch rear. Kind of a big wheel feel.
    Power up grades are always a benefit. I have heard of a 10. To 1 piston and maybe a good port and polish would make a noticeable improvement may be a 350 carb and exhaust. I'm sure the auto clutch is the limiting factory, I am not sure how much hp it can handle. But at some point you realize there is no perfect machine. But for me the sx/350x are the two most well rounded.

    Thanks
    MrC.

  6. #6
    Join Date
    Apr 2012
    Location
    MI, USA
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    I haven't looked into hopping up the 250es/sx much, but in theory the TRX350D or TRX300 should have a similar primary clutch. If I recall right, the 250es/sx clutch has 4 ears that come out while the bigger models had 5. Not sure if the physical size changed though. The secondary clutch (trans input) you can get heavier springs and such to handle more hp.

    I'm not sure if I'd like the small rear tires + bit front tire. You can adjust the angle the machine sits a little with the shock mounts, you'd just need longer shocks to increase the front height but I'd think it would make the handling worse. It's set within a pretty small range for a reason I'd think unless you're going more for looks over function.

    I agree, I wish Honda made a shaft drive sports 3 wheeler with a similar power plant to the 350x. Some day I'll have to tear down the TRX350D machine I have and see just how similar it is to the 250es/sx. The bottom end design is similar to the 250es/sx but the top end is effectively a 350x engine. I think even the head interchanges.

    https://www.partzilla.com/catalog/ho...big-red/clutch

    https://www.partzilla.com/catalog/ho...man-4x4/clutch

  7. #7
    Join Date
    Apr 2011
    Location
    Mexico
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    7,911
    I think if you post 10 more times and wait until you’ve been registered for a month that you will be able to post photos.

  8. #8
    Join Date
    Nov 2019
    Location
    Florida
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    I get its a security concern, but the first thing new people want to do is share a pic of there bike, ask a question with a photo to show the problem.
    I am here for the long haul, like I am on another atv site dedicated to hondas.

    Ps2fixer- i am sure you are right about the handling worsening with so large a tire in the front. Bottom line I would hate to buy wheels and tires for my new to me sx and they either not fit, and under preform. I was thinking the light wheels would be a plus, and dropping to a 20 in rear would get it a little more grunt of of the corner.

    El Camexican - thanks for the heads up

    MrC.

  9. #9
    Join Date
    May 2006
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    N.E. Ohio
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    Would you consider the SuperX200 other than shaft drive it’s a winner of a build. 86’ 200X roller with a 86’TRX200 motor and electric harnessing system pretty much bolt up. You can do the 250cc upgrade to boost output but not a must have. Auto clutch, electric start, and reverse...just more to consider.

  10. #10
    Join Date
    Nov 2019
    Location
    Florida
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    Tri-Z 250- Now your just trying to confuse me, yes you are correct that would be a contender.
    I am going to need a bigger shop.

    MrC.

  11. #11
    Join Date
    May 2006
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    N.E. Ohio
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    It’s not to confuse you, sorry for that. It’s just that the SX is a tank of a trail machine and a Sporty work horse. The SuperX strips the bulk, adds suspension performance, with some after market upgrades. It retains the sport work horse auto motor and trans on a chassis you can push harder on.


    3WW has a few really GOOD posts on these mishmash builds. If anything you might find inspiration for your build.

  12. #12
    Join Date
    Nov 2019
    Location
    Florida
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    Tri-Z 250- That does sound like a fun project. To be honest I don't see cutting up this SX, its so complete and original, I have been looking hard for a real project, so far just a few 110's and a 185.
    I promise you if, I run across a 200x or a 350x, I will pick it up. That said, I have considered picking up a 400ex, there cheap, fast and "Honda", I could see mounting a 200x or 350x front end on one of those. It would not be for work, strictly play.
    Thinking out loud here, cutting the stem off a trike and grafting it on the 400ex frame isn't that hard, only real concern it what angle of rake and getting it true. Of course you loose the auto clutch, shaft drive and reverse which is whats so nice about the sx platform. Like many have said, there is no perfect bike that does everything, that why we need several to fill any voids, just like in guns and cars.

    MrC.

  13. #13
    Join Date
    Apr 2012
    Location
    MI, USA
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    Yea the 200x, 250r, and 350x all start with better suspension mainly because they were designed for more extreme riding and all have chain drive. The 250sx is the sportiest shaft drive that I know of. I heard/read there's some trx models that were made within the last like 10 years that were sport + shaft drive but know little to nothing about them, I think they where 250cc.

    The auto x is a pretty common build, never heard of this super x, but it seems to be the same concept except using a trx 200 series engine instead of an atc one. I looked up the models for 86 because I didn't recognize the model + year combo, I suspect it's the TRX200SX. The actual TRX200 (no letter) was released in 1990 and only lasted till 1991. I think the TRX200D is effectively the same machine (91-97). I've looked at the 2000 and older machines way too much in the last year lol.

    If you want to talk about tanks, check out the ATC250ES =) pretty sure that was the heaviest Honda 3 wheeler, something like 100lbs heavier than the 250sx... actually let me grab the specs.

    250sx - 364lbs
    250es - 406-410lbs (guess I overshot a bit for my guess)

    350x - 320lbs
    83-85 200x - 282lbs
    86-87 200x - 278lbs
    81-84 250r - 302lbs
    85-86 250r - 289-291lbs

    Just for fun, here's a "smaller" shaft drive machine...

    84 200es - 375lbs

    Since weights are kind of interesting to check out side by side I compiled some data together from service manuals and brochures. I just did a quick run through the ATC and FL models since there's a million TRX models lol.

    http://atvmanual.com/honda/atv-weight-by-model

  14. #14
    Join Date
    May 2006
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    N.E. Ohio
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    Quote Originally Posted by ps2fixer View Post
    Yea the 200x, 250r, and 350x all start with better suspension mainly because they were designed for more extreme riding and all have chain drive. The 250sx is the sportiest shaft drive that I know of. I heard/read there's some trx models that were made within the last like 10 years that were sport + shaft drive but know little to nothing about them, I think they where 250cc.

    The auto x is a pretty common build, never heard of this super x, but it seems to be the same concept except using a trx 200 series engine instead of an atc one. I looked up the models for 86 because I didn't recognize the model + year combo, I suspect it's the TRX200SX. The actual TRX200 (no letter) was released in 1990 and only lasted till 1991. I think the TRX200D is effectively the same machine (91-97). I've looked at the 2000 and older machines way too much in the last year lol.

    If you want to talk about tanks, check out the ATC250ES =) pretty sure that was the heaviest Honda 3 wheeler, something like 100lbs heavier than the 250sx... actually let me grab the specs.

    250sx - 364lbs
    250es - 406-410lbs (guess I overshot a bit for my guess)

    350x - 320lbs
    83-85 200x - 282lbs
    86-87 200x - 278lbs
    81-84 250r - 302lbs
    85-86 250r - 289-291lbs

    Just for fun, here's a "smaller" shaft drive machine...

    84 200es - 375lbs

    Since weights are kind of interesting to check out side by side I compiled some data together from service manuals and brochures. I just did a quick run through the ATC and FL models since there's a million TRX models lol.

    http://atvmanual.com/honda/atv-weight-by-model
    Itís the quad version of the SX 2x4 motor combo from 86í My mistake thanks for catching it.

  15. #15
    Join Date
    Apr 2012
    Location
    MI, USA
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    Not a problem, wasn't trying to bash your details or anything, I just know when I read threads like this and there's no letter at the end of models, or the year is missing, it makes the data really hard to follow to actually be put into use. Like just saying a TRX400 engine swap is kind of pointless with out the year since there was a EX and X and I think there is 2 main versions of the EX. Can't remember why the 400 comes to mind, was something I researched and had to dig deeper into to find solid info on an interchange, might have been the CDI.

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