The Saga Begins: January 2000
Up until KTM re-embraced linkage rear suspension a couple years ago,
anyone who owned a 1998 and newer KTM had the PDS damping
system, which is pretty cool because there's no shock linkage to
maintain. One slight problem, though: the bearing in the lower shock
mount is a teflon coated heim-type bearing (sometimes referred to as
spherical-type). The heim isn't the problem; actually it is necessary to
handle the slight side-to-side movement that would destroy a
conventional bearing in no time. The KTM engineers decided to use a
bearing with a "maintenance-free" teflon coated race. In theory, good
choice. In reality, bad choice. Because of the various movements of
the swingarm, the seals can't keep out all the dirt and water from
contaminating the teflon coating (the seals actually move around a bit).
Normally you would smear a bunch of grease in the heim and around
the seals, but that's bad, because the grease breaks down the teflon
coating. So you're kinda darned if you do, darned if you don't grease
the thing. Without any servicing at all (as with mine the first year I
owned my KTM), the teflon breaks down after 60 or 70 hours of use
and play develops in the swingarm. I found this out by putting the bike
on a stand and lifting up and down on the swingarm. The end of the
swingarm had about 1/4 inch of movement before engaging the
What's the solution?
Prolonging the life is about all you can hope for. In the early days of
PDS, a KTM dealer was about the only option for find a replacement,
and back then KTM's parts were expensive. The first time I replaced the
bearing, seals and spacers in January 2000, I think I paid about $100.
That was tough to swallow, so I began wrapping the lower shock mount
with an old inner tube (see below). The goal was to keep as much
water, dirt, and mud from contaminating the heim's teflon coating. Also,
I would regularly pull out the seals and smear a light layer of waterproof
grease around the edges. My second heim bearing lasted about 100
hours, so these precautions added 30-40 hours to its useful life.
Over time, PDS-equipped KTM's were all over the trails and tracks, so
an after-market gradually developed for the heim bearing. In response,
KTM actually started reducing their OEM prices for the bearing kit.
Companies like Enduro Engineering now sell the heim kit for about $30,
which is a lot more reasonable than it used to be.
One thing I would recommend is buying a heim bearing tool. I used to
drive the bearing in and out of the swingarm with a socket and
sledgehammer, but many years ago I bought a special tool from a
now-defunct company called eRider. This tool greatly reduced the risk
of driving the bearing cockeyed and putting grooves in the housing.
Motion Pro makes a nice tool, but if you're careful, the socket and
sledgehammer method still works.
Heim Removal & Installation
1. Remove the swingarm. Not completely necessary, but you need to
grease the swingarm bearings anyway. Don't forget - gotta take off the
chain guide, too.
2. Pop out the bushings using a drift or other long metal object. Work
at them from within, attacking them from the opposite sides. After a
year of corrosion, they may need some persuasion.
3. Pop out the seals around the heim bearing using a flat blade
4. Use a socket or heim bearing tool to drive out the bad heim. Pound
on it like hell, and use some heat around the housing if it won't budge.
Be careful not to get the bearing mis-aligned on the way out or it will dig
into the soft aluminum housing. If this happens, a Dremel tool or file
can be used to smooth off any rough spots. The heim can be removed
from either side.
5. Line up the new bearing and start tapping it gently until you know it's
going in straight. A night in the freezer (the bearing, not you) helps with
installation. If you're using a socket as a driver, make sure it is only
contacting the outer race and not the round thingie that swivels inside
(you DON'T want to ruin your new bearing, trust me). Then pound like
hell until it's centered in the housing.
6. Tap in the new seals (don't even think about trying to re-use the old
ones). A little dab of grease around the seal lips is a good idea.
7. Put in the new bushings.
8. Re-assemble the swingarm and shock.
|Not pretty, but effective
|Here's how I used to try extending the life of my heim bearing. There are some
aftermarket alternatives to this now. The life of the heim will depend on your riding
conditions. If you like to play in the mud, plan on a shorter life.