Major problems associated with turning a 2002 KTM 125 into an Adventure Bike?

Discussion in '2 smokers' started by Sp4rks, Aug 4, 2013.

  1. Sp4rks

    Sp4rks Been here awhile

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    Alright guys, this is my first thread(Hi my name is Sp4rks, I'm new here, blah, blah, blah) based on my bike. Now, that is my '02 KTM 125sx, started life as a competition ready MX bike, it was neglected, after I bought it, I started getting it ready for more enduro riding, after fixing/ getting fixed all the stuff that was wrong with it. Now, I was looking at some numbers, and it looks like this bike makes more power(But with much less weight, stock) than a KLR650R, one of the preferred "low end"(But nearly indestructible) bikes on this forum. So, I figured, 2 stroke 125 adventure bike? Why the hell not. I'm 17, giving me the ability to make up my lack of experiance with poor judgment, and beat up on my body by going on an adventure with a 125cc 2 stroke mx bike. Of course, there's some problems(and non-problems) with trying to do this. Here's my list


    Problems:
    • Gas mileage(Acerbis makes a 6.6 gallon tank for this bike, that settles that, if I need more range, I'll add a baja designs rear auxiliary gas tank)
    • Cooling(After market over-sized radiators, assuming they'll fit with the Acerbis gas tank)
    • Oil Capacity(Don't have a solution, maybe an external stator that increases capacity?)
    • Powerband(Space out the gearing, toss in a flywheel for good measure)
    • Power(75W Stator, I don't need much, just for lights and GPS, don't even need enough to start with, it's kickstart only, I don't plan on using heated grips, or other comfort stuff)
    • Durability(The frame needs to able to handle enough gear for where ever I go, that's the only problem I see so far, other stuff such as pipe armor, skid plate, and handguards are readily available
    • Fairing(Some wind-protection would be nice, if I could find a rally style fairing for this bike, that'd be great, if not, a mountable windshield would be fine)
    • Luggage(I need to carry stuff, water proof would be nice)


      Non-Problems(Basically, stuff that doesn't matter to me)
    • Vibrations(Unless it shakes the welds loose, I handle some vibes, I'll toss in some inserts on the pegs if anything)
    • Comfort(SDG seat is pretty nice and I already got it, heated grips, passengers, noise, and the like is stuff I don't think I need, mostly because I intend to exploit the benefits of being a 17 year old male, such as being able to be hard on my body because it's nearing it's prime)

    Anything else I missed? Once I get started, I'll either post here in the "two smokes" forum or the "some assembly required(speaking of which, where would this conversion go?). And out of curiousity, has anyone else(Other than that guy that tried to do Paris Dakar on a KTM 150xc, yes, really) tried something similar to this? A 2 stroke adventure bike built from a modern 2 motocross bike?
    #1
  2. tHEtREV

    tHEtREV Encouragement award recipient. tEAM iDIOT.

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    I tried to make a 2000 200EXC into a long distance bike, but gave up after one trip.

    Big advantage of the 2stroke is weight, but mine chewed so much fuel that I had to carry so much to get anywhere that it became as heavy as most 4 strokes.

    I was using 10 liters per 100k so it ended up being cheeper to tow the bike were I wanted to go riding instead of riding so I lost interest.

    Lack of carrying ability was a worry too, but I only planned on using it as an overnighter.

    I also had other bikes that were much better suited to long distance stuff (640ADV and a 525) but if it was my only bike I would have kept at it.

    The 6.6 gal tank also needs some brackets and fiddling to make fit (at least mine would have).

    It could be done though.

    And Louise(sp) finished the Dakar this year, but from what I was told, he left a trail of pistons behind him.:lol3
    #2
  3. Sp4rks

    Sp4rks Been here awhile

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    Well, the Acerbis tank is designed specifically for this model, and I also intend to use it for only one or two day trips(Mostly to get to this Adventure Park that's a 1:45 trip away and has 200+ miles of trails, no sticker needed, get out of school on Friday, head over there, camp out, Friday and Saturday night, return Sunday night). And commuting. As far as pistons, would a bore kit take away from the time needed between rebuild? If not, I could use the extra power.
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  4. Twin-shocker

    Twin-shocker Long timer

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    Its certainly possible to use an MX bike for trail riding, but the cost of the conversion work, fuel consumption, and very frequent rebuilds, means in almost all cases a 4T trail bike of some sort is a much better choice.
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  5. Forde

    Forde Been here awhile

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    it might make more peak HP than a KLR but the KLR has way more torque and a better spread of power. also the ktm will be unreliable and is too small to carry gear if you are going on a real adventure.
    #5
  6. tHEtREV

    tHEtREV Encouragement award recipient. tEAM iDIOT.

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    I have only seen two part numbers for the 6.6 tank, one for natural and one for orange.

    I could certainly be wrong on that but I know when I bought mine I only had those two options.

    Regardless of that I can't see you needing one if you are going to be near fuel, and I would avoid getting one unless you absolutely have to, they are big wide tanks and seem to ruin the nimble feel of the bike.

    I had a rear Baja designs tank and a 11l IMS and found that I didn't notice the weight to much.

    [​IMG]

    I wouldn't hesitate to take my old 200 on a trip down the highway, I did a few 45 min trips, whole day of riding and then ride home trips on it and a 300 or so hundred Klm dash in the poring rain down the highway at 110Kph once.

    And while I am not saying it can't be done, I am going to have to agree with Twin shocker on this one.
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  7. Twin-shocker

    Twin-shocker Long timer

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    People often ask about using trials bikes for trail riding, and again while its completely feasible, the downsides are in most cases greater than the advantages, and I would guess a small capacity MX bike is even less suited to trail use.
    #7
  8. Grreatdog

    Grreatdog Long timer Supporter

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    My MXC200 is a better trail bike than an SX but it still sucks as traditional dual sport. The close ratio box and instant power that allow it to blow away damn near anything else I have ever ridden on goat trails is hell on the highway.

    With the highest gearing I can reasonably run highway speed is right at the powerband hit. So roads aren't much fun. Even with extra flywheel weight it is a beast at highway speeds. And, as said, it uses as much gas as my truck.

    That said, when I was you age I rode all over hell and creation on a two stroke 125. So if it is all you have then go for it. Putting myself through the wringer when I was young is what makes for the best stories now that I am an old fart.

    But if you plan to spend a bunch of money getting it ready, then I would just sell it and buy an old EXC for cheap.
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  9. B_C_Ries

    B_C_Ries Long timer

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    Fabricate some sort of rack for the back, strap on a plastic gas can, a sleeping bag, a sheet of canvas, and a small bag with extra socks and underwear.
    Do about 500 miles on a nice scenic road and decide if a 125 Adventure Bike will be right for you.

    If it was me, I wouldn't put too much money into this project. I would just get rolling. You're 17 so you should be able to handle some discomfort and exposure to the elements.

    Hit the road and enjoy the trip. When I was 18 I bought a POS Honda SL350 for $300. Lots of my friends kept telling me how they were going to get better bikes and how mine was a ratty piece of junk, but I was rolling and that is what matters most.

    You will most likely get tired of the 125 pretty soon, but you will enjoy remembering and talking about your early shoestring budget trips for a very long time.
    #9
  10. 81cr450

    81cr450 Been here awhile

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    I'm of the mind that your on the right path Grasshoppa. Alot of guys on here wouldnt ride anything but a 4-poke with auto pilot & enough gear that it takes an hour just get into or out of it. & your getting off the couch & "doing" something, not just living in the alternate reality of video games or internet :clap.

    From what I understand, you want to ride to a recreation area set a base camp then play. A "framed" backpack will work to hold a night or 2 worth of gear & if you get one with a lower bar to rest on the seat not all of the load is on you. I'm assuming your in the 150-175 lb range , so even 50 lbs of gear wont seriously overload the bike.

    The piston is pretty simple get a forged one & it should go for a bit. The narrow trans ratio is gonna be a hard one with that bike. You'll wanna go up like 2 teeth on your counter shaft sprocket to get near a 55 mph cruise speed. Take off will suck. I'd personally look at a wide-ratio trans acording to this finding one should be easy

    http://www.ebay.com/itm/5-speed-Tra...Parts_Accessories&hash=item2ec620aafd&vxp=mtr

    While your in the motor replace the main bearings w/quality ones, seals, & a rod. You'll be taxing it & it'll be best if it's fresh. If the plating in the bore looks good, no flaking, just put in the new forged piston.

    If that has the adjustable power valve you can hopefully tune out some of the hit at cruise speed. Cruise speed's will be like 55, your not gonna want to ring it out WFO for mile after mile. Think scenic highway not freeway.

    The lighting kit & licensing , might be next to impossible where you live. What state , as others from there might be able to chime in & help you? I just did a plate on a rmx 250 I spent like $200 on a tusk lighting kit & battery, $110 to register it, $100 for a years insurance.

    All this does assume you want to do the work yourself as part of the fun.
    #10
  11. Sp4rks

    Sp4rks Been here awhile

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    Actually, I weigh 135lbs(5ft, 9 in tall), I can still carry a decent sized pack though. I already have a silencer(FMF Shorty) that favors low end power, and an expansion chamber(FMF Fatty) that broadens the powerband. So, I'll gear up the counter-shaft and see what it does for me(I did however, go 2 up on the back to bring 1st and 2nd closer together, so I might go 3 up on the front). Worse case, yeah, I'll put in the new transmission(stock is a 6 speed transmission, oddly enough). Texas is really relaxed on making a dirt bike street legal, street legal tires, speedometer, horn, one mirror, lights, and some reflectors(Nope, don't need turn signals). Get it inspected, go request a title change at DMV with the title and form from inspector, request change over. Should be relatively simple procedure, thanks for the advice. Engine was strong last time is was checked(certified KTM mechanic). So, once I need a new top end, I'll put in the 134 kit. Thanks, once I get started I'll start posting pics in the 2 smoke forum as previously mentioned.
    #11
  12. Twin-shocker

    Twin-shocker Long timer

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    If you seriously want to use an old 125 MX bike for trail riding, and dont want to suffer major issues with the motor, then I would suggest a full rebuild using OE or good quality pattern parts, and maybe reduce the compression a little to lower the amount of heat being produced, which should help to extend engine life.

    You will also need to service top end on a frequent basis, and I would guess replace pistons quite often. All in all though setting issues with the motor aside, the major thing you need to be thinking about is what sort of mileage you are wanting to do, and will you be able to access fuel no problem?

    You can of course fit large capacity fuel tanks etc, but that might mean that most of the advantages of having a 125 Mx bike will be lost. Using a 125 MX bike for trail riding, is a bit like using a hacksaw to make something out of wood.................its certainly possible, but far from ideal.
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  13. Grreatdog

    Grreatdog Long timer Supporter

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    55mph is probably being generous with a SX125. On my MXC200 I went two teeth larger at the countershaft up to a 15 tooth which is the limit with a hydraulic clutch. That sprocket puts the chain scary close to the slave cylinder. I also went to a 45 tooth rear. It doesn't really hurt the acceleration. It will still lift the front wheel easily. I added a flywheel weight to calm it down even geared like that.

    But even with a six speed and that seriously high gearing it still isn't happy running 55 mph. It will do it but I have to dial the power valve up to the top of the rpm range to get it to behave. Otherwise it is hell since the hard hit is right at 50ish. The bike really wants to be ridden around 45 to 50 mph on the highway to stay below the hard hit and serious fuel guzzling. The close ratio box just isn't meant for the highway.

    I have been watching eBay for an EXC transmission but may just bite the bullet and order a new 5th and 6th gear set to match the EXC or XC-W ratios. If the OP goes transmission shopping an EXC six speed wide ratio with the "overdrive" sixth gear would be the hot ticket.

    For the OP's stated use I wouldn't sweat reliability. Just be cool and don't ride it pinned forever on the highway. Mine is an 01 and was just torn down for a new top end. The cylinder was still perfect, the crank seals good and the bottom end tight. A new piston, rings, minor head mod, power valve service and carb cleaning was a little less $500 including shipping both ways.

    Like I said before, I wouldn't put any real money into that bike because it just isn't going to be cost effective in the long run. Though it would be educational for sure. I would just try the ride described and see how it goes. If it sucks, which it likely will, sell the beast and try to find something more suitable.
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  14. Foot dragger

    Foot dragger singletracker

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    An SX125 has no lighting coil,be tricky getting lights on it,money would be involved. Close ratio trans useless on the street,youd be in 6th gear halfway down the block,Ive tried it.

    20 mpg wouldnt get far even with a 6 gallon tank,piston life is longer then a japanese 125,but not too long compared to any 650 single.
    But really I think this idea has only just popped in to your head, and will go no farther then this thread,like many blue sky threads.:rofl
    #14
  15. orangebear

    orangebear Long timer

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    Sale the bike. And then get a bomb proof 4/ and then hit the road.
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  16. Twin-shocker

    Twin-shocker Long timer

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    Thats pretty much spot on, and I guess is advice that can be applied to pretty much any 2T MX bike, whose owner is wanting to use it for trail riding?
    #16
  17. orangebear

    orangebear Long timer

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    Only matter if you ride in the dark. I road a mx bike on the road with no lights front or rear and never had a problem
    #17
  18. Grreatdog

    Grreatdog Long timer Supporter

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    It is only around $100 to add a lighting stator to an SX anyway. The ones I have seen only put out enough to power a 35/35 headlight plus LED taillight and signals. So you aren't going to be burning holes in the darkness or powering a GS like array of gadgetry. But it will get the bike past inspection and get you home at night. To be honest, the 35/35 on my 200 isn't that much worse than the headlight on my 640.
    #18
  19. davesupreme

    davesupreme grand poobah

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    i've been dreaming about a plated 200 for awhile.... i think you can keep your crank, put a 200 barrel and piston on that and make it a 175, the 200 has a longer stroke... check it out, that's what i'd do if i was gonna rebuild... 125 to 130 something ain't gonna be much.... there's a guy on the KTMTalk forum, andrew cooksey who does the 2-stroke cranks, he's in tejas too... sounds like a great guy....
    #19
  20. Navin

    Navin Long timer

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    I have a true wide ratio WR125 Husky. Forget it. I hate to ride it the 6-7 minutes at 35 MPH to the trail head in 6th gear, and that is just about it for comfortable cruise speed. Yeah, It'll do near 60 MPH as top speed I guess, but that isn't a speed you'd just ride it at on the streets. I'd guess you could gear it to do 45-50 but it won't move off the line and forget trail riding like that.

    I'd not worry about the frame or carrying weight, that will be fine. It will vibrate itself to death if you go down the road for a few hours IMO.

    As a trail bike they are great if ridden at race pace. Slipping the clutch, WFO, carry speed and gear it low. Street is misery.

    The oil capacity is just transmission BTW. You are "changing" the motor oil every engine revolution. I'd not worry about that at all. Bigger rads either. These bikes run cool when a 4t is boiling over, non issue.
    #20