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Trials Bike Build/conversion?

Discussion in 'Trials' started by rizzer, Jun 23, 2011.

  1. REALGRAVEROBBER

    REALGRAVEROBBER LEAVING GRAVES EMPTY

    Joined:
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    Oddometer:
    878
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    GFY, Montana
    Just discovering this great thread!

    For years I've thought that a 1986-On Honda XR200 chassis, and an engine like the RT180 Yamaha engine would be good ingredients.

    RT180 Desirable aspects:
    -Inexpensive, reliable, an old tough design.
    -Cooling system self contained, can file or grind down fins for clearance.
    -Could use or ditch the oil injection system.
    -Narrow, relatively light weight.
    -Big flywheel, made for grunt of a trail bike.
    [​IMG]

    [​IMG] [​IMG]

    Xr200 desirable aspects:
    Brakes are drum (narrow, cheap, reliable, light).
    Steel tubular chassis, easily mod'd by the home tinkerer.
    -Seat, tank, and fender mounts easily mod'd for your wants (adjust rake, shorten, etc).
    - 18 & 21 wheels, big clearance for rear tire.

    Big square shape engine bay to accept engines:
    [​IMG]

    Had I not found the following 03 Beta 250 Rev3 recently for a good deal $1,500.00 (30 days ago), I would want to build such a xr200-rt180 bike:

    [​IMG]

    [​IMG]

    Honestly having a newer used (15 years old is new to me!) hasn't made me ride any better. Just being honest.
    #81
  2. MATTY

    MATTY BORDER RAIDER

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    Interesting thread with some equally interesting bikes, i think loosing enough weight to make it truly competitive would be difficult on say a typical Dual sport bike, i do feel you could however make a worthwhile unique trials bike if you thought about the donor / build bike.
    The small 125 to 200cc Chinese CG 125 clones would be a feasible option i feel. i have a Parts bike i got with a Minimalist build project my son subsequently stole the main bike from to play with and promptly destroyed gradually any practicality in continuing thus leaving the parts bike lost and unloved but reading this thread i decided to get it running and do some thing with it Trials like conversion.
    I had considered this several times in recent weeks but reading this today i am on it! I went out not a hour ago and adding new fuel had the little 150cc single thumping away so the heart is good we got life! So i have decided to take it further.
    We have had several of these china clone CGs one is still thriving after several years as a play bike round the place, the kids did not kill it and they did try hard too.
    this donor parts machine is very stripped but functional all there, to achieve road worthiness even in its most basic form totally impractical, but as trials conversion fodder its perfect.
    I will make a point of creating it on this thread as i think its a thread needs far more input its interesting and i think even if you already got a trials bike only good can come of building something out of scrap in any spare time you might want to fill, my winter night just got more interesting today, it sure beats the heck out of staying in watching the TV set lets put it that way. Anybody else got a dead bike lurking unloved in the back shed they could re incarnate .?
    #82
  3. Greebe

    Greebe Been here awhile

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    A used trials bike might make more sense.
    #83
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  4. MATTY

    MATTY BORDER RAIDER

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    I totally agree and if all a rider wants is a trials bike to ride and is not interested in the unique or does not have the time or need the challenge in their life, a late 90s/ early 2000s bike would be better and perhaps cheaper in the final analysis. But for the less serious competitors and those who perhaps just want something of their own its an option some might want to consider.
    In my case we are falling over Trials bikes here as it is and dont need another, but re purposing back shed clutter could just get some thing with having .
    #84
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  5. Norman Foley

    Norman Foley Devotee of the Husqvarna Supporter

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    I'm a Husky guy, so always wanted to build a replica of the Husky prototype trials bike from the 70's. Andy Elliott from HVA Factory in the UK built one a few years ago. At some point I'll start putting aside the parts to do the build.
    [​IMG]
    #85
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  6. motobene

    motobene Motoing for 49 years Supporter

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    Something like that Yamaha motor 175 to 200cc would be my preferred engine to build a custom trials bike around. I'd also use a Hodaka 250 engine to get more displacement but with Hodaka's compact ball-lock transmission. But Hodaka 250 is a rare machine and I don't know if the clutch is a good design.
    #86
  7. Achro

    Achro Adventurer

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    [​IMG]
    Anybody know anything about this bike? Taken from the MAVT website. Looks like a TY250 cradle with modded sub frame, bodywork, and tank. Maybe swingarm extended?
    #87
  8. dave_d

    dave_d Adventurer

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    NY

    There's a few of those bikes floating around the western NY area, Most belonging to members of NTR (http://www.ntrclub.org/). They're all custom builds, I believe some were built with TY250 motors, at least one with a BSA 441, and 2 owned by the Miller brothers (http://millerranchtrials.com/), have Honda 200x motors. They used to have some info about them here, http://millerranchtrials.com/cool-bikes/ , but it seems like the pictures are gone now. I did find this picture of one of the Honda powered machines. If you need more info, the Millers contact info is on their webpage, and i'm sure they'd be happy to answer any questions you have.

    index.jpg
    #88
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  9. 2whlrcr

    2whlrcr gooligan

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    How about a bigger picture of that Honda framed bike?
    #89
  10. oldtrialer

    oldtrialer Trials since 74

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    The green bike is Chad Busswood at Candytown MC. He has test ridden Expert sections on it to try them out. The bike works very well.
    #90
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  11. Achro

    Achro Adventurer

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    Thanks for the info @dave_d and @oldtrialer. Those bikes are really cool. Hopefully I'll meet one of those dudes and learn more about the fab on those bikes.
    #91
  12. Brewtus

    Brewtus Buffoonery, Inc.

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    Interesting build. Not to sound like That Guy, but isn't that an awful lot of faith in those upper shock mounts?
    #92
  13. Achro

    Achro Adventurer

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    I hear you... Maybe those tabs are L shaped? Or square stock?

    This got me thinking. Does anybody have experience with changing shock and swingarm angles? I'd be more interested in qualitative descriptions of how it changes the feel of the bike. The forces involved obviously vary from frame to frame and shock to shock...
    #93
  14. Brewtus

    Brewtus Buffoonery, Inc.

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    Dunno, can't tell by the pic. Hope so, because from the angle it appears to be just a tab and a bolt. Gotta be more than that...
    #94
  15. Junglejeff1

    Junglejeff1 Long timer

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    Back in the 90,s I purchased a very used IT 175 with a bad tranny.I collected a lot of old bikes back then and put a transmission and shift drum out of a 79 yz 125 in it.Those old yami,s had many parts that were interchangeable.It lowered the gearing into trials territory with the stock sprockets.bike would top out at 35 to 40 but was a blast to ride.
    #95
  16. MATTY

    MATTY BORDER RAIDER

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    The NTR bike pics look good, a build along these lines is where i think conversions become a real practicality for those wanting to undertake the job.
    a build on a mono shock bike would be good to see if any exist, the more bike pics the more to draw ideas from.
    #96
  17. motobene

    motobene Motoing for 49 years Supporter

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    I've researched a potential cheap source for trials engines for custom builds and found the 1988 to 2006 Yamaha YFS200 Blaster 4 wheeler may be a great source for engines. The Blaster had a simple air-cooled 2-stroke 200 with 6-speed transmission and small-format engine:

    https://en.wikipedia.org/wiki/Yamaha_Blaster

    These were produced in volume. You can buy whole machines cheaper than buying salvage engines, especially redneck specials. Parts can be inexpensive. On eBay I saw multiple examples of piston assembly AND the cylinder for under $80!

    Yamaha BYFS 200 Blaster Engine Right.JPG
    Yes, that's oil injection clutter on living in the primary cover.

    Lots of available parts:
    Yamaha YFS 200 Blaster Whole Top End.JPG

    And kit stuff like 240cc top ends:
    Yamaha YFS 240 Blaster Top End Kit.JPG
    #97
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  18. Brewtus

    Brewtus Buffoonery, Inc.

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    Makes me wonder if one of these would fit in a TY175 donor, quadbilly gearing notwithstanding.....:hmmmmm
    #98
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  19. Luke

    Luke GPoET&P

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    [​IMG]

    Blasters? I think they're great motors.

    Not a trials bike, obviously, but a trail bike. This was a YZ125.

    I've gone a little nuts modifying it, but all it really needs are a PWK28 and some heavy clutch springs. Many of mods that you can buy are crap- they increase the top end at the expense of bottom end. Fortunately there are good mods (like chambering the head) that are super easy and can be done at home, or done cheaply by pros. There's a ton of helpful information and spare parts for them too.
    #99
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  20. motomofo

    motomofo Been here awhile

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    There was a guy who showed up to a few state series events here in TX a few years back who used a Montesa 315R chassis, converted it to twin shocks, machined his own brake drums and shoehorned a Yamaha Blaster motor into it. It was an interesting machine, and the coolest part was he claimed that he could easily bolt all of the original parts back up and have a regular, stock 315R again.
    MATTY, jonnyc21 and Brewtus like this.