looking to make a trail/desert bike out of a 98 YZ250

Discussion in '2 smokers' started by sect8dr, Jul 26, 2012.

  1. sect8dr

    sect8dr ride them all

    Joined:
    Nov 20, 2010
    Oddometer:
    257
    Location:
    middle of nothing illinois
    Looking at a 98 YZ on Sat and I am starting to get ideas in my head about turning it into something that would be decent in the woods and maybe not so bad in the desert. The bike belongs to a friend of mine and appears to be in pretty rough shape so this will probably be a long rebuild, which is not so bad since i am going to be off of work for a while anyway. So far the list in my head looks like this:


    bigger tank
    new wheels/tires
    skid plate
    new chassis bearings
    seat


    If anyone notices anything i miss feel free to chime in and call me a dumbass. Any suggestions on which brand of what or what size of this or that will be heard and appreciated. The engine in this bike is supposed to run 'awesome' in the words of my mostly alcholic buddy. I will know more about the bike on Sat, but will most likely own it as i have a tendency to buy bikes without too much thought. It does have a clear title and i will be making it street legal with a bigger stator. Does anyone make a fan kit for this bike with a bigger stator? Guess i will have to find out.
    #1
  2. KZJohn

    KZJohn Been here awhile

    Joined:
    Aug 15, 2008
    Oddometer:
    450
    Location:
    Anaheim Hills
    The YZ makes a great all around bike. We use a 98 YZ125 for pre-running in Baja all the time, just geared it up. We even left the 19" rear wheel on it. Zero problems, just stay on top of the maint. I don't know about making it street legal, (not an option here in the People's Republic of California). I have been using battery operated HID lights on it.
    #2
  3. anonny

    anonny What could go wrong?

    Joined:
    Mar 20, 2007
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    6,066
    Location:
    Beautiful Revelstoke BC
    Should make a decent toy but I wonder if there something that can be done about the close ratio gearbox.
    #3
  4. The Letter J

    The Letter J Long timer

    Joined:
    Aug 17, 2010
    Oddometer:
    1,452
    Location:
    Santa Maria, CA
    I recall several threads over on thumpertalk discussing (with part #'s) how to install factory yamaha wide ratio (just 3-5 or 1-5 if you care to do some grinding inside your yz cases) gears from a WR model. It's sleepy time for me but a search over there is sure to give the answers... http://www.thumpertalk.com/topic/457937-transmission-gear-swap-yamaha-yz250-3-4-5-wr4xx/
    #4
  5. sect8dr

    sect8dr ride them all

    Joined:
    Nov 20, 2010
    Oddometer:
    257
    Location:
    middle of nothing illinois
    Brought the bike home for $400 today. Nothing great to look at but it does run pretty decent, has a couple carb issues and does not want to idle but other than that everything functions as it should and other than an overflow tube from the carb doesn't seem to have an major leaks. I will try and post up some pics tomorrow evening after i ahev had time to dig into the good stuff.
    #5
  6. sect8dr

    sect8dr ride them all

    Joined:
    Nov 20, 2010
    Oddometer:
    257
    Location:
    middle of nothing illinois
    Checked the bike over and have discovered that it is in fact a 96, well the frame is anyway. The drain plug is stripped out, and the high idle problem is deffinantly an air leak of some sort. No pics yet but i will try and work on that.
    #6
  7. KZJohn

    KZJohn Been here awhile

    Joined:
    Aug 15, 2008
    Oddometer:
    450
    Location:
    Anaheim Hills
    Use an oil squirt can with premix oil in it. Put the oil on all of the intake tract gasket areas,( carb boot down stream, reed cage, center case gasket, etc,), while the bike is running. When it starts to smoke from the exhaust you have found your vacume leak.
    #7
  8. Twin-shocker

    Twin-shocker Long timer

    Joined:
    Jan 28, 2012
    Oddometer:
    1,673
    I would guess your air leak is almost certainly caused by main bearing play, which is allowing air in through the crank seals. Remove the ignition cover, and check for play on the crank, if there is any you have found your problem.

    Main thing with this type of project though, is the cost of repairs required to a bike that old will very often be more than you would be able to find something in good condition for. So before anything else work out exactly what the repairs are likely to cost, before making any decision to go ahead with the project.
    #8
  9. 2trally

    2trally Adventurer

    Joined:
    Aug 2, 2012
    Oddometer:
    62
    Location:
    Arizona
    It seems to me that it would be possible to keep 1-3 the stock close ratio and convert 4-5 into the wider ratio. Gives you the best of both worlds.
    #9
  10. sect8dr

    sect8dr ride them all

    Joined:
    Nov 20, 2010
    Oddometer:
    257
    Location:
    middle of nothing illinois
    Really doesn't matter about the cost to value ratio on this project. This project will not be a fast one and I only have a few hundred bucks in it so far. But it will be a slow going project as i am in the middle of turning a Grand cherokee into an adventure vehicle in its own right. Going to be taking some time off of work this Fall and will hopefully have both projects running by Christmas. Already looking into a top to bottom rebuild and the WR 4-5 gears, just tring to figure out if I am going to try it or if I need to find a decent mechanic anywhere near East central Illinois. If anyone knows a good 2 smoke mechanic, let me know I will pay good money to find a reputable wrench in my area.
    #10
  11. 2trally

    2trally Adventurer

    Joined:
    Aug 2, 2012
    Oddometer:
    62
    Location:
    Arizona
    I just read the thumpertalk link a little more thoroughly... and thats almost exactly what they do. :doh
    #11