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Discussion in 'Thumpers' started by Pablo83, Sep 14, 2010.
The new arm is here. After some cleaning, it's looks great.
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.
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:
:eek1 Great info!
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.
I finally had some time to get back to this project.
holes drilled in the new swingarm:
I finally got to use this fancy tool. I've had it for years and never used it.
I made the shape in cardboard first, then aluminum
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.
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.
I weighted the swingarm before and after. These modifications added 13oz.
Why did you do that?
Nice work! Hard to believe how much more stout that looks.
Start with post #2
Yes I am subscribed, but I am not seeing the point Pablo
to reduce swingarm flex.
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.
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.
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.
I'm removing the manual decomp from this bike. Where do I find a plug to cover the hole in the valve cover?
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.
Or... try to find a core plug in the right size?
Yes, I was really wondering if these are available.
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.
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.
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?