Making it handle
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
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.
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
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.
posted by veloandy at 8:56 AM
3 Comments:
hey mate, glad to see your bike is doing well. i left you a comment a few months back with some queries about my own xs400, and am pleased to say that aside from getting occassionally stuck in neutral, its running beautifully. Ive been noticing that my fuel consumption is a little higher than i would have expected. I generally get 250km on a tank, including reserve (running out of petrol on the side of the road was a nice experience). I think i may be either revving the bike too high or too low in the gears, which may be burning more fuel than necessary. If you wouldnt mind helping me, how many miles do you manage to get off a tank? and around about how many revs do you generally keep your bike at for each gear?
i hope this isnt too much trouble, i have been enjoying working on this bike, and hopefully will one day have the budget to do the kinds of modifications you have, yours looks great.
Thanks again, Dave
your fork gaiters will not help with the stiction in the fork.
stiction is "sticky friction" between the fork seals and the internal slide bushings that has to be overcome to move the fork, puting a gaitor over the seal and slider will not chance the ammount of friction that exists. the gaitors do have a function. it is partly cosmetic and partly functional, cosmetic first, it is a very retro look and servs to hide the chrome of the fork slider to give a "darker" look. functionally, they protect the fork seal from dirt and debris, and they protect the fork slider. if the forc slider were to take a stone hit (or similar) it could create a sharp edge that would dammage the fork seal (if the sharp edge were to travel past the seal) when the damage to the seal is bad enough it would eventually leak fork oil and the fork would become ineffective and the oil could dammage the brake pads if it dripped that far.
love the ionfo and article links. i am trying to build a cafe race style 400. i am in the parts acquire mode right now.
can you tell me more about what it took to fit your "loaf tank"?
Hey Eric,
You're right that most of the stiction is between the fork seals and the fork leg, and adding a fork gaiter doesn't do anything about that...HOWEVER, to add a fork gaiter, you have to take off the dust wiper (basically a rubber cap that the fork leg passes through, that covers the seal). I was hoping that would make a difference, but I was surprised how little friction there was between the dust wiper and the fork leg - I bet it didn't make any kind of difference.
I do like how the gaiters look, though...and keeping crap off the fork legs (and preventing nicks from rocks, etc.) is sure to make the seals last longer.
I didn't end up liking how the "loaf tank" looked...it's sitting in my garage now - if you're interested, I'll send it to you for the price of shipping. It fit right on, except that it didn't have reliefs along the backbone-tunnel to clear the coils. To get it to "fit", I sat it on the bike, traced around where the coils were with a perminent marker, and pounded out dents where I had marked with a 5lb engineer hammer. It was crude, but it got the tank to fit. Too bad it didn't look nearly as nice as the stock "custom" tank.
I have taken a bunch of new pictures and have a bunch of updates to post, but I haven't gotten around to it yet...I'm surprised how much traffic this site is getting, though. I hope to post an update soon. BTW: The Harley shocks didn't work -- the eyelets were too wide to fit in the frame pockets at the top mounting point.
Good luck with your cafe racer! Let me know how it goes!
Later,
-Andy
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