Dual-sporting a Honda TL250

Discussion in 'Old's Cool' started by jtn, Feb 7, 2012.

  1. jtn

    jtn Been here awhile

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    Hi folks, I've had some great input here before on other projects so I thought I'd put this one out there too.

    I've got a 1976 TL250 (one of the classic Honda trials bikes) bored out to a 360 and was left to sit since the mid-80's. The bike has a lot of memories and nostalgic value in it, so yes, for what I'm planning for it I could probably get a newer/faster/shiny-er bike but that's not really the point with this build. I'm looking more for making a bike with a lot of stories in it fantastically ridable.

    The basic goal is to get it into excellent running shape, looking awesome, and make it street legal. A couple quick initial tests show that the high tension plug wire is corroded and I'm getting 60psi compression, which I'm hoping is due to some gunk on the valve seats.

    A couple of pre-work photos:

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    Thanks in advance folks -- this will be fun.


    Some questions for the gurus out there:

    The original gearing is way low for trials riding, and I've heard that I could swap out a 76-78 XL tranny. Anyone ever done this or have one they want to sell? I know Honda used alot of the same parts on this era bike. It would be great to have some master part-number cross ref list -- anyone heard of any such thing?

    I want the brightest headlights I can get on this thing, so I'm planning on swapping out an XL stator (and maybe rewinding it? I'm not sure there are extra empty coils on it so I'm not sure if it would make a difference . . .) and using the Trailtech regulator/rectifier along with LED turns/rear/brake. I'd love to put the Trailtech 8" Halogen Race light on, but it takes 55W.
    http://trailtech.net/8in_race_light_kits.html

    A couple of useful sites I've found so far:

    http://www.thumpertalk.com/topic/560660-changing-from-6v-to-12v/
    http://www.thumpertalk.com/topic/870123-1976-tl-250-rehab/
    #1
  2. fgrep

    fgrep n00b

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    Don't know your location, but in California you would need a battery, as
    you must be able to run taillight, horn, signals(?) without engine running.

    this site has the code for honda part numbers:

    http://www.kaila.net/tl125/tl125partcode.html
    #2
  3. Growl

    Growl Adventurer

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    I can relate, having converted a Yamaha TY250 trials bike to dual sport use in the late 1970's... I added a mirror, larger tail light, and the factory option bigger seat. It was a good experience overall and I even did some touring BUT the trials bike had some inherent limitations that lead to a couple dangerous close calls on the street. Consider upgrading the brakes... perhaps adapt a front end which has a disk brake AND consider stretching the wheelbase... makes the bike more predictable and controllable at speed... probably could adapt a longer swingarm. I am not suggesting a radical stretch... maybe 2 or 3 inches.

    The transmission is probably fine... just raise overall gearing with a smaller rear sprocket.
    #3
  4. jtn

    jtn Been here awhile

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    I hear you about the brake -- that stock thing is tiny.

    Anyone know a 35mm fork/wheel disc combo that I could swap out? I'd like to keep the stock triple tree to keep things simple . . .

    Got it started the other day after cleaning the points, carb, and replacing the spark boot. Kudos to the folks who stored it back in the mid-80's.

    An example of how clean the guts were:

    [​IMG]
    #4
  5. jtn

    jtn Been here awhile

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    Turns out there's an extra TL engine I've got and a '70 cl350 frame . . . hmmmm . . .

    [​IMG]

    And I haven't done a rebuild yet that didn't have visitors like these in it:

    [​IMG]
    #5
  6. pennswoodsed

    pennswoodsed lizards,bugs and me

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    Rather than expensive trans mods , 1 tooth up on countershaft, the trail seat or xl seat , find a swingarm that will fit or weld 2 inch bent extension ,fork brace ,and fit any front wheel with better brake that will fit. Honda used lots of stuff that should work.Oh do anything to increase light output. This came with a battery ,didn't it ? As long as you are not shooting for desert sled ,these were great single track bikes. Oh yeah ,and could be ridden like a speedway bike,full lock and wheel spinning.
    Regs,Ed
    #6
  7. jtn

    jtn Been here awhile

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    Found a '75 CB500T front end with a single hydraulic disk. Used the All Balls Racing site and a set of calipers to find replacement tapered bearings, cut & re-welded the CB triple tree shorter to fit in the TL frame (with an interior sleeve to add strength), welded a turn stop on the frame, and am rebuilding the brake master and caliper with new seals/pads and a stainless line. Found the easiest way to do a fork swap was to replace everything rather than find the matching fork dia/wheel spacing/height/etc.

    http://www.allballsracing.com/index.php/forkconversion

    Forks got new seals/oil and the engine blacked out:

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    #7
  8. OldPete

    OldPete Be aware

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    Nice work! :*sip*

    Wasp nests. Kill'em with spray but leave the nest, that way they don't return.
    Used to get those by my porch light and they always came back until i just left the dead nest inplace.

    Yes, i know it is on the bike but you gotta have them nesting in the garage or around the house.
    #8
  9. McJamie

    McJamie STROMINATOR

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    Brake cleaner also kills the buggers. We got swarmed one day at the garage door, and it was all I had. They just drop to the ground instantly.
    In 1986 Cycle World voted the TL250 as best dual sport that year, so it should work just fine.
    #9
  10. aDangerousBusiness

    aDangerousBusiness Always Working

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    late to the thread, but I'm also rebuilding a TL250 (frame no. TL250-1000408) and the frame I've got doesn't look anything like yours. Did the previous owner do custom work on it or perhaps it's a later model with a TL250 motor thrown in? Looks pretty trick.

    This isn't my image, but it's what my frame looks like
    [​IMG]

    As to the front brake, I had the same trouble trying to find a disk that would fit and couldn't come up with a solution that wasn't much different than yours. I'm going to try arcing the drums (mostly 'cause I'm curious to try it) and see what I can squeeze out of the original brake in a best-case-scenario. :D
    #10
  11. jtn

    jtn Been here awhile

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    It's a custom frame, I'm not sure who fabbed it but I know this bike was at one time a vintage sidecar observed trials bike (hows that for specialized?). What is 'arcing the drums'? I'm assuming its like turning the drums on a car? If so, can you just take them to a brake shop? The reason I ask is that I have a couple other 70's bikes with drum brakes in front that need to be freshened up.
    #11
  12. aDangerousBusiness

    aDangerousBusiness Always Working

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    It's funny you mention it, because the one I've got was also set up with a trials sidecar. My dad bought it from a guy back in Tenn back in the 80s. I actually found his contact information in the original papers we got at the time of sale and got back in touch with him a few months ago to ask him some questions about the bike.

    He used to compete in nationals with it. I asked him if he made the sidecar and he said he didn't, that it was a BKS that he'd imported from England. I looked into that and it turns out the "BK" in BKS is just Barry Kefford (Sidecars) - a now-elderly gentleman living outside Birmingham.

    I did a little more digging to get in touch with him and had a few interesting email and phone conversations; including him sending me a bunch of photos of the sidecars he'd made and his years serving as the starting flag man at the Isle of Mann races. Pretty cool stuff. I'm and idiot and don't have those with me right now or I'd scan them it. I do have a picture of the frame though:

    [​IMG]

    As for brake arcing, yeah, it's the same as what you'd do on cars to get the pads and the braking surface to mate as accurately as possible. I used to be way more common when drum brakes were state of the art. I'm sure you could find some old 50's motorcycle articles that detail exactly how to do it - these days the information is a little harder to find. There are a few shops that do the procedure but I don't think you'd have any luck at a basic brake shop (or even a basic motorcycle shop).

    Vintage Brake has a single-sentence tip on doing it yourself (at the very bottom) and there's a slightly better explanation on the RaceTech site - though I don't exactly understand what their setup is there. Some buddies and I have a machine shop in Oakland, CA so I'll be giving it a shot myself in the next couple months, throwing it up on the mill or lathe (it's definitely on the list... just not super high up there).

    Some people say the difference is huge, but that's usually guys racing on big vintage street drums... I'm not sure you're ever going to be doing stoppies on the tiny TL250 hubs. But who knows...

    -Conn
    #12
  13. jtn

    jtn Been here awhile

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    That's pretty neat, I wouldn't have guessed there would be so many sidecar stories with these bikes. As far as the rear drums, thinking I'll put in some new brake pads in and see how it does.

    Just finished drilling out the front rotor inspired by an article in Iron & Air (awesome photography in there!)

    http://ironandair.com/issues/

    and setting up for some new Dunlops:

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    #13
  14. jbcaddy

    jbcaddy Long timer

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    Wow, two trial hacks being dehacked! and I was hopeing to find what you are taking apart. Oh well, prolly could not find a person to be a monkey anyway :deal
    #14
  15. kingrickman

    kingrickman n00b

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    JTN , Did you ever finish the dual sport TL project ? If you have given up would you consider selling it ?
    #15
  16. pommie john

    pommie john Long timer

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    How did you get on drilling the disc? I have heard that they are very hard. Do you need a special drill bit?
    #16
  17. jtn

    jtn Been here awhile

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    #17
  18. jtn

    jtn Been here awhile

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    Lots of cutting oil, drilled a pilot hole, and lower spindle speeds, but otherwise just used my regular bit set, then chamfered the hole. I believe the discs of this era were cast iron and I didn't find it especially hard -- if you have access to a mill I'm sure a proper end mill would be smoother. Maybe someone with a better knowledge of disc brake metallurgy could pipe in here?

    Found the instructions on how to do it in an issue of Iron & Air -- maybe about a hear ago?
    #18