Wednesday, January 30, 2013

Sizing Up The Swingarm Options

I like most things about the DR350's design, but one thing I can't get past is the rear swingarm.  It's clunky looking and those fins have not aged well.  I'm sure the three-piece design was cheaper to manufacture than a welded, boxed aluminum design that can be seen on almost every modern dirt bike, but it's also far more flexible with the open C-channels.  Most DR owners agree that the rear swing arm is the DR's biggest weak area.

I have been toying with the idea of swapping it out in favor of something else.  Since I am not too concerned about suspension curves (maybe I should be more so) and I have no issues cutting or adding tabs to the frame to support new linkage mounts, my options are broad.  So broad in fact that I put #2's swingarm side-by-side against one I have from a CRF450.  Granted, the linkage designs are wildly different, but it's eerie to see how similar they are despite their 15 year design gap and different manufacturers.

1991 DR350S swingarm in the background, 2005 CRF450X in the foreground.  The DR swingarm is at least twice the weight of the CRF swingarm.
DR350 swingarm in the background, CRF450X in the foreground.  The pivots are aligned, which helps show the added length of the CRF swingarm.

There are a couple dimensions that really give this wild idea some traction: both swingarms take a 17mm pivot axle, and the CRF swingarm is 5mm narrower at the main pivot than the DR swingarm.  That doesn't mean a swap like this one, or any other, will be remotely easy, but it does mean I won't have to modify the frame-side of the main pivot.  Just say'n...

For the fun of it, I placed my components in their places.  That's #2's frame, the DT250/400 tank, #2's forks (lowered 3.5"), an 18" CRF rear rim floating in the front, a CRF swing arm, and #2's rear 18" rear wheel.  Mentally photoshop some tires and a different, more road-race-esque rear section, and we are in business.


  1. Hey, someone on the same trail as I am. I'd be real interested in seeing how you could make that CRF linkage fit in. I have a 98DR w/441cc kit and would like to swap over a 99 YZ250 rolling chassis's stuff to it, you might just motivate me! Thx, JR

  2. Oh, the elusive 1998 DR350. If you do swap over the YZ's suspension goodies, make sure those forks end up on eBay. The 1998-1999 DR350s came with cartridge forks and are quite sought after by DR enthusiasts.

    Do you have a build thread, blog, or place to monitor progress? I would like to see your project.

  3. Thanks for that- I would prob be smarter to just leave the bike as equipped and do some mods to make it less sponge-like, but it seems that valve kits and rebuild fees will prob cost me more than the time and the 'already-sitting-there' YZ parts. My DR is actually VIN'd as a 97 but was made in 03/97 and has the 98 suspension. My wish was mainly to try to make it feel at least no heavier than a DRZ and I'm guessing some heavier springs alone would accomplish that, but I am a skinny 6'6" so to make it taller, lighter and even an inch or 2 longer seems like a good idea. Your post about the weight of the stock swingarm surprised me, made me think that thing has gotta go. (I'm so old, initially I thought those fins looked neat!) I have done some engine swaps/frame modding a few times, but never blogged it, maybe some day..

    1. The DR swingarm is a heavy bugger compared to modern offerings. There's no denying that. However, as far as aesthetics are concerned, I have to eat my words. If you haven't already seen, check out this DR350 swingarm swap and mod to a CR500:

      Those fins look pretty sexy on that application.