See the tapered section of the KTM drain bolt just above the threaded portion? If
the copper washer falls off, that taper will ruin the threads in your engine cases.
I MESSED UP MY 450SXF DRAIN BOLT
I replaced the oil in my 2017 KTM 450SXF, but when I got the job done,
it leaked oil out of the drain plug on the side of the engine. So, I drained it
again, but this time I cross-threaded the drain-plug bolt. Now I have wrecked
the threads. What can I do to fix this?
First, you need to understand how this happened. We’d guess that when
you pulled the drain plug out to change the oil, you failed to notice that the
copper drain-bolt washer fell off. Then, when you reinstalled the drain bolt
(sans copper washer), it threaded into the engine cases too far (since the copper washer is used to achieve the desired length of the drain bolt). Without
the copper washer, the tapered and unthreaded shaft of the drain bolt rolled
the first threads on the engine cases over. When this happens, the bolt will
feel cross-threaded when you try to take it out or put it in the engine cases.
Since you kept trying to put the drain bolt in, you messed up the threads
on your cases and probably the threads on the drain bolt. All of this happened because you lost the $2.95 copper washer. You’re lucky that you did
this on a KTM 450SXF, which has an easily accessible drain bolt (below the
shift lever). If you did it on a 250SXF or 350SXF, you would find that you
can’t access the drain-bolt hole to chase the threads without removing the
engine from the frame. The best solution is to clean up the threads in the
cases with a tap to make sure that the first threads will allow a new bolt to
get started—and you will need a new drain bolt and copper washer.
If you don’t have a tap-and-die set to chase the threads, the backyard fix
is to take a new drain bolt and carefully start it into the drain-bolt hole. This
shade-tree repair can be done on the 250SXF, 350SXF and 450SXF without
any fancy tools. You must make sure that you have the drain bolt properly
aligned. Once you are sure that it will thread into the drain hole in a straight
line, thread the new bolt in and out slowly, using the new bolt to clean up
the threads that are damaged in the cases. Only the first couple threads were
damaged by the tapered shaft of the drain bolt (when it went in past the end
of the threads because the copper washer was missing). Once you have the
threads cleaned up, gently tighten the new drain bolt and copper washer.
Don’t overdo the tightening.
The wire backfire screen protects
the air filter from flames.
WHERE THERE IS SMOKE…
I’ve always wondered if it’s
true that an air filter can catch
fire. I’ve never seen a burning air
filter in all my years of racing.
Yes. It doesn’t happen very
often, but there is a kernel of
truth to it. Four-strokes have been
known to backfire and catch the
air filter on fire. It isn’t a common occurrence, but it happened
enough times that in 2012, Honda
actually doubled up the backfire
screen on the CRF450. It should
be noted that the MXA wrecking
crew has removed the backfire
screens from our four-strokes for
years (and never called the fire
department once). That said, you
can order special flame-resistant
air filter oil from DT1 (www.
dt1filters.com) that will work on
any brand of filter, while Twin Air
makes special air filters that are
made from flame-resistant foam