Top Gun Motorcycles
Technical Insights
by Elden Carl
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12/01/2008

Adjustable Pre-Load Fork Caps, by Elden Carl

We understand that among the new products released recently are pre-load adjustable
fork caps for the KLR650. If you are constantly changing the weight carried forward of
where the seat and gas tank meet they might be helpful. If not, they're superfluous. It's
more important to have Schrader valves in your fork caps (like the pre-'o8 KLR650). As
the ambient temperature changes or you get a temporary pressure buildup due to long
hard riding, you can get rid of excess air by pressing on the Schrader’s. On a cold
morning your Schraders allow you to reverse the process.  

A properly set-up conventional fork has:
A.  Balanced compression and rebound action.
B.  Springs of the proper rate (never use air as a spring supplement). Note: DR650s and
pre-'08 KLR650s come with decent spring rates if you don't carry a lot of weight forward of
your family jewels or ride excessively over rough ground).
C.  Suspension fluid of the correct type and viscosity and the oil level set so as to achieve
the correct pressure build-up during compression action (kinda like adding extra pre-load).

My DR650's didn't come with Schraders so I installed the fork cap relief air valves from
Motion-Pro which just require the press of a finger to equalize pressure.

The pre-'08 KLR650, which we much prefer over the '08 for off-road, comes with Schrader
valves in the fork caps, but when I get time I'll install the Motion-Pro valves (which are
quicker and don't require a valve).

We at Top Gun seldom need to make pre-load changes in front because we never carry
any significant extra weight forward of the family jewels. Even when Pauline is on board,
the front end pre-load requirements don't change because her 118 pounds, the
"workenest" 118 pounds in KLR-dom, are carried directly over the rear axle (Note: We do
use progressive springs up front on Pauline's bike).

By the way, the rear spring and damping requirements on our KLR650 change
dramatically when Pauline and our gear are onboard (gross weight approximately 750lbs).
Her Ohlins shock has increased damping and a 9.0kg spring (my spring is a 6.5kg).

Riding quickly and safely especially off-road requires not only skill, but properly set-up
chassis and suspension. Having a bike that has its wheels constantly in contact with the
surface and that provides a stable chassis makes all the difference when it comes to
getting where you're going comfortably and safely (at 74 and 81 years respectively, we'd
like to continue keeping the old bodies separated from the hard ground).

If you have a KLR650, start by replacing your woefully weak rear spring with one from Top
Gun.  If you have a DR650, you're OK at both ends unless you weigh much over 200 lbs.
Cheers
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