Pablo's DR350

Discussion in 'Thumpers' started by Pablo83, Sep 14, 2010.

  1. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    I have been riding a plated '01 Yamaha WR426 for the last few years and it's a very capable bike, but I'd like something that requires less maintenance and has a six speed gearbox. As part of my low maintenance requirement, I wanted something air-cooled. After researching many bikes, it appears that the DR350 is the largest displacement air-cooled dirt bike that come with a 6-speed tranny and and weighs less than 300 lbs.

    So last winter I bought a '98 DR350 kicker.

    [​IMG]
    #1
  2. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    The first thing I noticed about the 350 is it appears to have a hinge somewhere in the middle of the bike. I had heard that the frame on this bike is very flexible and that turns out to be the case. I got used to the handling pretty quick, but this is still something I want to fix.

    Shortly after buying the bike I found a used 440cc big bore kit for it on CL, it appears to be a kit sold by Jesse a while back. I have yet to install it.

    After reading this post in DisTech's DR350 rebuild (which has been a real inspiration), I decided I wanted the DR250S's tranny. I recently acquired the second half of my winter project, a '91 DR250S. Here are my two DR's:

    [​IMG]
    #2
  3. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    So here's the plan...

    From the 250 I will use:
    Frame (since it's a titled, street-legal vehicle)
    Tranny
    Rear hub (has cush drive)
    Wiring (assuming the 250's alternator rotor will fit on the 350's crank).

    From the 350 I will use:
    Crank
    Head
    Suspension - I understand the '98 kicker has cartridge forks and the 250 only has damper rods.

    Additional modifications will include:
    440cc big bore kit
    Removing the "hinge" - I think a big cause of this is the 3-piece C-section swingarm. The plan is to weld the swingarm arms to the center section and use some aluminum strap to box in the C-section arms. A fork brace wouldn't hurt either.

    More input is welcome, just keep in mind this will be a budget build (no USD suspension, FCR carb, or Vortex air-box [although I might build my own airbox as the stock one is clearly restrictive])
    #3
  4. Pablo83

    Pablo83 Sleep, Wrench, Ride

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  5. ShooterDave

    ShooterDave Adventurer

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    WOW. :eek1 :eek1 :eek1 That is quite a winter project. Good luck and keep us posted. I don't own either of these but am interested in following your progress.
    #5
  6. plugeye

    plugeye mc caregiver

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    i like the sound of this
    #6
  7. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    I spent this morning re-reading DisTech's build. There's an enormous amount of information there. I just need to clean some Transalp parts out of the shop before I start this build.
    #7
  8. CodeMonkee

    CodeMonkee Geek Adventurer

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  9. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    Since this is a budget build, I'll try to track the cost of everything since some people seem to be interested in that kind of thing. Items begin with N or U for new or used.

    U 98 DR350 - $1100
    U 91 DR250S - $950
    U 440 big bore kit - $175
    Acerbis tank $207
    aluminum plate for swingarm: $98
    peg extension $30 (I think)
    Cycra hand guards w/ ATV mounts: like $110 I think
    protaper bars $70ish

    [EDIT] shortly after posting this list I stopped keeping track. I certainly went way over budget. Overall I would guess this bike is slightly cheaper to maintain than a modern CRF/WR/RFS, but not a whole lot cheaper.
    #9
  10. Kawidad

    Kawidad Long timer

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    Yes it is true. The 98 and beyond had cartridge forks that were sourced from the previous generation RM race bikes. Also, they improved the shock, IIRC, they were also sourced from the RM. In addition, the brakes were RM brakes. So, all in all, big improvements. :thumb
    #10
  11. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    Just a little background on the project...

    In college I rode a friend's chopped out GS1100 with open headers. It was an absolute turd. I really didn't have much respect for Suzuki's after that.

    A while back it seemed like everyone was trying to get me to buy a KTM, but I had the impression they were terribly unreliable, so I did a survey to try and understand if my impression of KTM's was true. That survey is here. There's a lot of information there, so the short form is, I tried to find the percent of people that rode each type of bike and compare that with the problems reported on each type. The data showed that KTM's were unreliable*, but the more surprising thing I learned from the survey was how many ADVers rode Suzuki's, and how few problems they reported.

    It was because of this survey that I started looking at Suzuki dirt bikes.

    *Now that I have a better understanding of KTM products and I have gone over the data again, it turns out that about 90% of the reported problems are with the LC4/8 engines which means the RFS engines are probably just as reliable as the Japanese manufactured bikes.
    #11
  12. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    Thanks!
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  13. motoman250f

    motoman250f Been here awhile

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    I would really try a fork brace before making a bunch of changes. it makes a huge difference.. Cool Project!
    #13
  14. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    For the front, I'm tentatively planning on just adding a brace. Do you use one? If so, what brand and how do you like it?
    #14
  15. DisTech

    DisTech Been here awhile

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    Awesome! :thumb

    You will need to get a DR350SE crank and starter clutch set (starter clutch, bearing and gear). I think the magneto will work but the dirt crank does not have room for a starter clutch set. Some pictures, here.

    Can't wait to see how you box the swingarm and how the bike turns out!

    :lurk
    #15
  16. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    Thanks for the help. Both of the DRs I'm working with are kickstart only. I saw the issues you were having on your build and asked about kickstart-only compatibility and you replied:

    So I'm assuming neither bike has a starter clutch and maybe I can use the 350 dirt crank??? Ultimately I just need to tear into both bikes and see what I'm working with. But I really appreciate any input you have.
    #16
  17. DisTech

    DisTech Been here awhile

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    I remember the question, sorry I didn't connect it with this thread. In this thread I was thinking you had an electric start DR250S. 93 was the first year electric start DR250, I should have checked.

    So, DR350 kick crank and big bore top end in a DR250S kick bottom end. That should go together nice. Looking forward to your progress.
    #17
  18. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    Excellent :thumb
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  19. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    Here are some weight measurements I took with some cheap bathroom scales. The first column is front tire weight, the second is rear and the third is total.

    98 DR350___121__137__258
    91 DR250S__126__165__291
    difference____5___28___33
    #19
  20. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    I should be making the initial parts order for this build next week (engine gaskets, rings, valve seals). Unfortunately I won't be able to get started on the build right away, as I have a couple XR engines builds that I need to get out of the way first.

    In the mean time I've been riding the two DR's a lot recently on some short trails in back of my house. I've had the 350 for nearly a year and I almost never use the decomp lever because the engine is so easy to turn over. I've wondered if that might indicate engine issues, but I don't have the right size adapter for my compression tester so that hasn't been checked. But the new-to-me DR250 is nearly impossible to kick over without the compression release, so my guess is the 350 needs some engine work.

    Despite the needed engine work, the 350 has loads more power than the 250, but that's not saying much. The 250 leaves a lot to be desired in the power department. If the difference between the 350 and the 440 big bore kit is as much as the difference between the 250 and the 350, I'll be a real happy camper.
    #20