Top Gun Motorcycles
Technical Insights
by Elden Carl
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07/01/2008

Shearing Forces and the KLR650

At first I wondered why Pauline and I with our gear all loaded onto the KLR650 never
broke a stock upper sub-frame bolt. With over 40,000 miles two-up on and off- road
carrying approximately 375lbs on the sub-frame, we should - according to the so called
experts on the Internet - have been bitten by the broken-bolt gremlin a long time ago.
What was different?  Number one, our stock bolts were properly loctited and torque, and
number two, we have never crashed. Number one is important because a properly
torqued bolt is much harder to shear off than a loose one. Number two counts because
crashing and whacking the rear of the sub-frame hard causes it to act like a long lever
against the two upper bolts that are very close together.

What’s can you do?
  • Install upgraded bolts (not blue ones with washers; they break - ask Jay Bass), and
    be sure to loctite and torque them into place.
  • If you crash and hit the sub-frame hard, replace all the sub-frame bolts .
  • Install 10mmX1.25 socket bolts which require a little drilling and tapping.  

We recommended this solution before the 2008 came out only to find this was Kawasaki’s
fix for the perceived problem (they got scared too). If these 10mm bolts are not loctited
and torqued they too may shear.

Whatever you do, avoid the $50.00 kit with the long/large bolt. Drilling all the way through
the welded-into-place collar is a bad idea since it has a considerably smaller outside
diameter inside the backbone than outside where your bolts are installed (you could
actually break through the wall inside the backbone).

Another potential bolt shearing problem concerns the 4 bolts that hold your handlebars in
place.  In stock configuration they are fine, but if you have bar risers that are flat on the
bottom and do not engage the area that the bottom half of the handlebars usually occupy,
you have a weakness.  A crash and a hard hit on the handlebars could cause excessive
shearing forces to be applied to the four fasteners. If you do crash with this type of riser in
place, it would be a good idea to replace the (4) bolts as well as the bent handlebars.

Radiator guards pose another potential shearing threat. Avoid any radiator or catch tank
guard that is anchored by only 6mm fasteners. The tiny 6mm bolts cannot sustain large
crash forces and could shear off, ruining the brackets and the radiator they are supposed
to protect.

We’ve only seen one good radiator guard, and that is from “Dual Star”. Crash forces are
absorbed mostly by the left front engine mounting bracket which the guard is welded to.
Real beefy! No guard is needed on the right; there is already a metal frame there behind
the right fairing shroud.  Shearing forces of lesser importance exist in other places on the
KLR650, but replacing all cheap #4 and #7 fasteners on the bike with high quality flange
bolts properly loctited and torqued into place will solve most potential problems.

P.S.  If you decide to install 10X1.25 socket bolts into your upper sub-frame, do not drill
and tap deeper than the existing holes.

KT-966 Blues

Dr. David Webster, long time MSM rider told me about the new King KT-966 tire back
when it first came out. Rod Morris and I tried and loved them for their long life and all
around usefulness. The KT-966 rear allowed us to use one rear tire for almost all
conditions. We’d just change the front to a Cheng Shin, 325/350-21, C-755 knobby when
conditions were sandy, muddy or otherwise loose.

We now find that this great and inexpensive tire is no longer available due to insurance
concerns (Lawyers again). It seems that if a manufacturer sells a DOT approved tire to a
distributor (in this case, “Western Power Sports”) it must come backed by liability
insurance.

Since King refused to insure their DOT tires, Western Power Sports dropped them. We
can only hope that King decides to remedy this situation so that we can again be supplied
with the wonderful KT-966 and their copies of the Metzeler Unicross knobbies which are
also
DOT approved but not insured. Wake up Mr. King, your customers are waiting.
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