Fuel For Thought
by Rod Morris
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Welcome To Fuel For Thought
Written by: Rod Morris
Glossary of terms and abbreviations:
MSM - Multisurface Motorcycles/Motorcyclist
MMP - Multisurface Motorcycle Products
TGMP - Top Gun Motorcycle Products
MSM Weight Classifications:
Lightweight (LW) - up to 250lbs
Middleweight (MW) - 251lbs - 300lbs
Light-Heavyweight (LHW) - 301lbs - 350lbs
Heavyweight (HW) - 351lbs - 400lbs
More KLR Shock Stuff
We seem to do more articles on the KLR650 shock than any other subject and there's
good reason. Every KLR650 from 1987 to present needs a spring upgrade.
There are a number of springs available through the aftermarket (how many we don't
know) including ours. Do they all fit properly, are they able to handle various load
weights safely - sad to say the answer is no. We know of one shock spring offered by
the aftermarket that actually came from an automobile. We don't know what vehicle it
fit, we only know that it didn't fit the KLR650 shock very well. It rubbed against the
center part of the swing arm and it was anybody’s guess as to what rate it offered. I
guess it was a "one fits all" situation. Well, that idea didn't work very well.
It wasn't until Elden Carl decided to consult with some suspension experts that any real
spring progress was made. I know Elden spent many hours talking with experts like
Charles Curnutt who invented the first long travel mono-shock back in the 1960's or
70's but I believe that most of the actual testing time was with Precision Concepts and
Stig Petterssen of Ohlins fame. Precision Concepts has provided quality suspension
set-ups for years, both to the regular weekend racers and the Honda Baja 1000 Race
Team with lots of input from the great Johnny Campbell who won about every type long
distance race there is. After Johnny retired, Robby Bell took his spot on the Honda
Team and is also winning on a regular basis. Just so happens Robby is the son of Bob
and Diane Bell, owners/operators of Precision Concepts with Bob as chief mechanic.
So, there was a lot of expert help in producing a top quality shock spring designed
specifically for the KLR650.
Part of the testing was to find out what rate the stock spring offered. As we like to work
in metric units, all of our numbers may seem a little foreign to some people but they still
show the difference. The stock KLR650 spring rated tested at about 5.1kg/mm. Our
first spring was 6.6kg/mm and worked well for total loads weight up to about 230lbs.
Total load weight is the rider with normal riding gear on and any added weight like
boxes, bags, bars, bash plate, tank bag etc. that is on the bike 90% of the time or how
the bike would be loaded on a daily basis. This is very important in order to get the
proper spring for your total load weight. After a period of time, we kept getting requests
for a spring that would handle total loads weights up to about 280lbs. After a little more
rate figuring we started producing a 7.4kg/mm spring. Then the big boys started calling
and saying, "hey what about me, I'm over 280lbs total load weight”. More figuring and
out came our 8.0kg/m spring which worked well to about 315lbs total load weight.
We've been asked about total load weights above 315 lbs and we considered an 8.5
kg/mm or even a 9.0kg/mm spring. This caused us to go back to our experts and we
were advised that anything over the 8.0kg/mm spring could possibly damage the pre-
load unit. If the pre-load unit breaks it means buying another shock (around $600)
because the pre-load unit is not available as a separate unit. Sometimes you can bid
on a used KLR650 shock on E-Bay or Craigslist but I haven't seen that many offered,
so take care of yours.
One part on the KLR650 shock that is overlooked a lot is the bump rubber.
Unfortunately, Kawasaki uses a very poor quality material in making their bump rubber
and consequently it will eventually go bad. There are a number of reasons why but the
two main reasons: some sort of corrosive material like oil, gas or even chain lube being
thrown onto the shock, and the wimpy stock shock spring. Your suspension should be
set to contact the bump rubber occasionally but lightly on the hardest hits. When you
start piling on a heavy rider, boxes and all the add-ons, the shock body slams down
with great force on the bump rubber, and much more frequently. You may remember
those surprise bumps that made the rear end go klunk; well, that’s the bump rubber
being crushed to about half its normal size. Add some of that corrosive stuff, poor
material with crushing blows and it won't take long to pulverize the bump rubber into
submission; whatever the cause, it will happen in time.
When we first introduced our 6.6kg spring we also had to find a way to remove the old
spring and install the new one. We made our first springs with closer inside tolerance
then the stock one because of the larger wire used and we were afraid the outside may
hit the swing arm. We found that it couldn't be installed from the bottom of the shock
like most are done so we designed our own spring compressor to do it from the top,
which wasn't easy operation either. We have since relaxed the inside diameter and our
current springs will install from either end.
When we were installing springs we would notice that the stock bump rubber was often
flaky, pieces missing, or crushed down and out of shape. The only fix was to take the
shock apart so you could slide the old one off and install a new stock one. Of course
that only meant that eventually the stock replacement would go bad again - now what
Well, along came Elden to the rescue again. After many more hours researching the
Kayaba shock it was decided that we could do KLR650 shock services ourselves. Not
only did we get genuine Kayaba parts but Elden found a racing bump rubber that
would withstand a beating and keep on ticking.
|After only 8000 miles, this bump
rubber has seen better days!
This whole article is leading to what I
discovered recently on a customer’s
KLR650 shock. I received a 2008
KLR650 shock that had 8,000 miles on
it. The customer wanted us to only
install a new shock spring. The 2008 to
present KLR shock has a plastic guard
around the shock body that's suppose
to help keep dirt and things away from
the shock shaft. When I first looked at
the shock I noticed that there was a
few pieces of material stuck around the
spring. I didn't like what I was seeing.
When I pulled the spring and plastic
guard off I found that half of the stock
bump rubber was missing (see photo).
There was a top part and a bottom part, but no middle. The parts that were still there
looked fairly normal; no oil staining or other obvious corrosives but the broken edges
looked like crumpled cork. I notified the customer with the bad news that the shock
would have to come apart to change the bump rubber and he OK’d the work.
Once the shock was apart and we could get a closer look at the bump rubber, we
decided that something corrosive had gotten on it and that the continual pounding while
riding was most probable cause of its demise. Only 8,000 miles - WOW.
Remember, every shock or front forks eventually need servicing so keep an eye out for
leaks or other abnormal things you may feel. In the case of the 2008 to present KLR
shock, the plastic guard won't allow you to see the bump rubber. Another side note on
the new model suspension is that the front and rear have 1" less travel then the
previous models and may let the shock body hit the bump rubber more often especially
when total load weight is high. Just one more reason to change that spring.