MR. KNOW IT ALL MR. KNOW IT ALL
Dear Mr. Know-it-all,
I have a 2005 KTM 250, and I’ve
noticed the muffler is getting a little
louder. I read about everyone com-
plaining about excessive noise taking
away riding areas, and I don’t want
to hurt my local area. When I took my
muffler apart, almost all of the pack-
ing was gone and the stuff that was
left was real oily. My riding buddies
told me I should just go to the hard-
ware store and buy some steel wool
instead of using the expensive muffler
packing sold by motorcycle shops.
They also say it will last four times
longer than fiberglass. I don’t want to
have to redo this because I used the
wrong packing. What do you think?
I applaud you for recognizing your
obnoxious exhaust. Between you and
me, I believe it is the single-biggest
fly in the ointment that dirt bikers
have to overcome. But I digress,
It is a consumable product, just like
tires, chains and sprockets. Having a
properly packed muffler goes farther
than simply keeping your bike quiet.
According to Donny Emler, owner
of FMF Racing, a blown-out muffler
can cause your engine to loose up to
four horsepower. Simply put, it has
to do with pressure waves that travel
through the entire exhaust system. By
using the proper packing material, this
pressure wave is unmodified and your
motor performs at its best. Steel wool
doesn’t offer the same density, which
is required for proper sound absorp-
tion and pressure wave performance.
Dear Mr. Knowing dude,
So my kid had his KTM 150XC
pinned the other day in fifth, and it
locked up solid. Seems he had got-
ten a stick in the radiator earlier in the
race and all of the coolant vanished.
I am slightly worried that the rod
may be bent. I don’t have the tools
or know-how to split the cases and
check it. Is there an easy way to get
an idea if it’s bent?
Well, dad of seizure boy, you can
go hillbilly on it if you’d like, and this
will give you a clue. First, the cylinder
needs to be removed. Also, removing the base gasket from the cases
is good, and then dig around for a
longer Phillips screwdriver. Place the
screwdriver through the wrist pin, and
lower the crank until the screwdriver
shank just starts to touch the base-gasket surface.
Since the wrist pin and the base-gasket surface should be parallel, or
in alignment with each other, you can
easily tell if the rod has been bent,
even slightly, by the distance between
the screwdriver and the surface.
Hopefully, they touch each other on
both sides at exactly the same time.
If so, then you are okay as far as rod
You can then remove the pin and
bearing and inspect the top rod and
pin surfaces for galling or seizure
marks. If okay, then it’s pretty safe
to assume the bottom-end bearing
is in usable shape. However, without
taking the crank apart, who knows
for sure. By the way, I’d consider it a
pretty good idea to purchase a decent
radiator guard, which would have
minimized the drama that you’re fac-
As always, you really should have
known, and I’m personally not liable
for your weirdness
Dear Mr. Know-it-all
So when I take my two-stroke up to
the high elevations, like 7–9000 feet,
in the summertime in Flagstaff and
ride the singletrack, it has a tendency
to kind of load up, even though I have
it jetted pretty well. Do you have any
suggestions to help this?
Well, Flagstaff loader, just curious
here: have you been hitting the pipe?
There are several thoughts that are
just wandering around my gray matter, the first one being bike brand, bike
size, bike year, current state of repair
and modifications to the steed? I do
have one thought: heat that dude up!
You see, when you’re at higher elevations, the pressure just isn’t in the
air like at the lower elevations, which
means the compression in the cylinder, the necessary heat and the resultant power are soft also.
The lack of heat creates a colder
running condition, especially in singletrack, where you are at lower throttle
openings and the engine is producing
little power. You can modify the head
and add compression head, or you
can go the frugal route and just run
lower octane gas.
Have you ever been to Colorado
and noticed that the have 86 octane at
the pumps? Why? Because they know
that the lower octane is an easy way
to make needed heat in your engine at
the higher elevations and lower temps
that you get there. So just try 89 or 87
octane gas instead of the normal 91
the next time, and watch your throttle
response and power and lack of loading up get better.