I really like my XS400, but I have started to notice its handling limitations.
It handles great on straight city streets and highways, up to about 55 or 60 MPH. That is mostly where I drive, so I don't usually have any problems.
However, it tends to feel like it wants to wander and twitch when I drive on gently curving streets at 40MPH (the limit on this particular road, BTW). Also, when accelerating away from a right turn, the back end feels slightly wobbly -- not planted at all.
On the interstate is where it is really scary. The interstate where I live has a speed limit of 75MPH, which means that people actually drive closer to 85MPH. It is built from sections of concrete with longitudinal rain grooves and tar-filled expansion joints about every 20 feet. The surface is cracked and ruined, but the cracks have been filled with big, bulbous tar snakes.
The engine in my XS400 is happy to push the bike up to 85MPH, but riding the bike on that surface is sickeningly scary. It feels like a rocking horse as it hits each expansion joint. The front wheel feels like it wants to follow the tar snakes and rain grooves. It doesn't go into a wobble or weave or anything, but it takes
a lot of concentration to ride.
I have aligned the wheels and verified the tire pressures without much improvement.
The lack of decent handling started to bother me so badly that I considered buying a different bike...but then I thought maybe I should look into if I could fix the handling of mine.
I did some research and found that Yamaha's XS650 (which is a much more popular bike than an XS 400) had a lot of the same handling problems from the factory. As far as I can tell, the main culprits are the fact that it used plastic swing arm bushings and barely-adequate steering head bearings.
This article on "The Minton Mods" describes how to make an XS650 handle well. This article claims that massive improvements in handling can be obtained if you
- Replace the plastic swing arm bushings with bronze bushings
- Replace the barely adequate steering head ball bearings with quality tapered roller bearings
- Modify the front forks to have less "sticktion" and less damping
- Buy decent rear shocks
I went to bikebandit.com, looked up swing arm bushings for an XS400 and an XS650 and saw that they use the same part number. www.MikesXS.com has bronze replacement swing arm bushings for $38.
Unfortunately, the steering head bearings are different between an XS650 and an XS400 so I can't get tapered roller bearings from MikesXS. Luckily, though, I found
a tapered roller steering head bearing conversion set for an XS 400 for $35.95, but I'm going to have to buy it from a local motorcycle shop. No big deal.
The Minton mods suggest drilling additional holes in the fork dampers to decrease over-damping. I'm a little wary of making such a drastic and permanent change. I think I'll just change the fork oil and replace it with 5W, filled up to six inches below the top of the fork tube. While the forks are apart, I think I'll replace the dust seals with fork girders from Mike's XS to reduce stiction a little bit.
Finally the shocks...I have often read that the factory shocks on Yamaha XS models are so bad that they appear to have no function other than preventing the springs from flying off. Unfortunately, nice new shocks are very expensive. Then I stumbled across a thread by a guy with a Harley Sportster who wanted to upgrade his rear shocks. He said he replaced them with some Progressive Suspension units which he hated, and then replaced the progressive suspension shocks with take off air shocks from a Harley touring bike -- a "wide glide", I think. I took a quick look at ebay, and there are a ton of cheap, adjustable Harley shocks that people took off immediately after buying the bike. I *think* these shocks would fit an XS400.
So...I have a new project. I expect the parts to cost close to $120, which is much less than another bike. I hope, by the end of the day, I'll have a motorcycle that is not sickeningly unstable on the interstate, feels rock-solid and planted on curving roads, and doesn't squirm when accelerating out of corners. I will update this blog with the progress.
