Pablo's DR350

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

  1. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    The new arm is here. After some cleaning, it's looks great.

    [​IMG]
    #61
  2. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    So I decided to finish destroying the old one just because I'm curious. I drilled off the heads of the bolt holding the arm on. Then I smacked it with a hammer until the epoxy broke. This took a lot of force. Here's what it looks like underneath.

    [​IMG]

    The round hole is the one I drilled, but as you can see, there was already a lightening hole molded into the inner part of the swingarm.

    I took a wire wheel to the swingarm to remove all the epoxy. Once the epoxy is gone you can go through the aluminum fast so it's a touchy process. After I removed all the epoxy and placed the arm back to the center section, there was enough slop that the swingarm would need to be placed in a jig to re-weld it. Clearly, trying to weld the arms to the center section is a failure on many levels and I won't be trying it again.

    I also learned that this bolt is not removable:

    [​IMG]
    #62
  3. DisTech

    DisTech Been here awhile

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    :eek1 Great info!
    #63
  4. frdbronco8

    frdbronco8 Been here awhile

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    Great info, thanks for figuring all of this out for us. Im looking forward to what you find out to decide what to do to mine.
    #64
  5. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    I finally had some time to get back to this project.

    holes drilled in the new swingarm:
    [​IMG]

    I finally got to use this fancy tool. I've had it for years and never used it.
    [​IMG]

    I made the shape in cardboard first, then aluminum

    [​IMG]

    [​IMG]

    And then I welded it all up. It was difficult welding the section around the brake bracket due to the difference in thickness of the pieces. The brake seems to mount just fine.
    [​IMG]

    And here's the other side finished. I later had to grind down the welds around the two chain-stay hole to get it to mount.
    [​IMG]

    I weighted the swingarm before and after. These modifications added 13oz.
    #65
  6. a1fa

    a1fa Throttle Jockey™

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    Why did you do that?
    #66
  7. DisTech

    DisTech Been here awhile

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    Nice work! Hard to believe how much more stout that looks.
    #67
  8. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    Start with post #2
    #68
  9. a1fa

    a1fa Throttle Jockey™

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    Yes I am subscribed, but I am not seeing the point Pablo :(
    #69
  10. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    to reduce swingarm flex.
    #70
  11. BikePilot

    BikePilot Long timer

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    Years ago when people rode DR350s hard Scotts sold stiffer swingarms that were said to make a huge improvement. I think Thumper also sold plates to be welded in just like you've done that were also reputed to be quite an upgrade. The swingarm is very flexy, just grabing and twisting the ends with the wheel removed it is notably less stiff than my XR or CR. Not an issue for casual dual sporting, but it does make it difficult to keep the bike pointed straight when the pace quickens.
    #71
  12. yondering

    yondering Long timer

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    How did you weld it without overheating/destroying the epoxy in the joints? Or do you know if you damaged it? The damage to the epoxy probably won't be visible.
    #72
  13. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    After my failed initial attempt to weld up the swingarm I ground out the welds, drilled out the bolts, and broke the epoxy so I could see how the swingarm was assembled. Despite all the welding I did on that swingarm, the epoxy was still incredibly hard to break, so I'm assuming it's still strong on this one.
    #73
  14. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    I'm removing the manual decomp from this bike. Where do I find a plug to cover the hole in the valve cover?
    #74
  15. 3uba296

    3uba296 Thumpcurious

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    Three ways to go..

    1: I did this om my -97 head with autodecomp that fore some reason had the manual decomp axle to. Since I had the cover loose I removed the seal, drilled the hole (with a stationary drill) to 10.5mm and tapped for M12 and loctited a M12 stop screw into it.

    2: If you don´t have the stuff to do this, simply keep the seal and modify (cut of) the part of the shaft that engages with the cam shaft.

    3: Remove the seal and plug the hole with a plug. Where to get it? Dunno. That´s why I did it my way. :D
    #75
  16. 3uba296

    3uba296 Thumpcurious

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    Or... try to find a core plug in the right size?
    #76
  17. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    Yes, I was really wondering if these are available.
    #77
  18. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    primary drive ratios:
    DR350 20:64 (3.200)
    DR250 22:62 (2.818)

    I'm led to believe that the lower ratio (from the 250) will be easier on the tranny and harder on the final drive. I'd rather be replacing chains/sprockets than trannies, so I'm going with the 250's primary.
    #78
  19. HeadTrauma

    HeadTrauma ¯\_(ツ)_/¯

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    Yeah, what the numerically lower ratio does is transfer less torque through the geartrain by making it spin faster. A numerically higher final drive is then required to multiply the torque back up again. That's why Honda's HRC kit for the XR600 included an NX650/XR650L primary drive set with a lower ratio.
    #79
  20. Pablo83

    Pablo83 Sleep, Wrench, Ride

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    I reviewed your comments on my NX build when I was deciding what promary to use. Thanks for all the help. BTW, since when are you into DR's?
    #80