MR. KNOW IT ALL MR. KNOW IT ALL
CROOKED VALVE STEMS,
Honorable Mr. KIA,
Most inner tubes come with two
nuts on the valve stem. I know that
one is to tighten against the washer
at the junction of the tube and the
stem. Isn’t the other one supposed to
tighten against the outside surface of
the rim? Otherwise, the stem can be
pulled crooked. My friends say I am
wrong. What do you say?
I say that you are wrong and that
you shouldn’t waste my talent on
infantile wagers. You are correct that
one nut should be snugged up on the
valve stem. The one on the outside of
the rim is used to hold the stem while
you install the tire. Once you have
put air in the tire, remove the nut or
back it up against the valve cap. That
way, if the tire slips on the rim, the
valve stem will get crooked but won’t
tear the stem off the tube. If you consistently see the valve stem getting
crooked, change to a new rim lock or
a second rim lock. If the rim lock is
functioning properly, there should not
be significant slipping on the rim.
STARTING SOMETHING NEW
Dear Mr. Know-It-All,
I have an early (2002) Yamaha
YZ250F. In most respects it has been
a very good bike. It doesn’t have
many miles on it, and the entire bike
is in good shape, so I would like to
keep it. The problem is starting. The
starting is so inconsistent that it has
been taking the fun out of rides. Is
there anything that I can do to make it
easier to start?
I see that you claim that your bike
is in good shape, but I find that claim
highly dubious. It is true that the early
YZ250F machines with the manual
compression release are not starting
perfection, but it shouldn’t be so difficult that it is ruining your ride. Before
you go ride again, check these things.
Valve clearance. If the valves are
tight, the starting will be extremely
erratic. If possible, have a shop do a
leak-down test on the engine to make
sure it is holding compression.
Replace the spark plug. Four-strokes rarely “foul” spark plugs, but
they do like new ones, and few owners bother to replace them.
Check the carburetor condition. The
earlier the FCR carburetor, the poorer
the dirt sealing was. The carb slide
has a wear plate on it. When it is new,
Once you have all those items
checked out and everything is set
properly, the starting should improve.
One problem is that you must find top
dead center every time you kick the
bike over, use the manual compres-
sion release to nudge it just past TDC,
then kick it. That is time-consuming.
You can install a later-model exhaust
cam or a Hot Cam. That will give you
an auto-decompression feature. No
more finding TDC. Just kick it and
go. If you take these steps, your bike
should be much easier to start.
Dear Mr. Know-It-All,
I am on a KTM 530EXC, and I love
the bike but not loving changing the
dual oil so much. The engine has
two screens under 13mm drain bolts
under the engine, but KTM makes the
bolts out of junk metal, and they are
so rounded that I can barely get them
out. Any suggestions?
My first suggestion is to get a clue.
You honestly believe that KTM would
choose “junk” to hold the oil in the
engine? That somewhat soft material
was chosen on purpose to keep ham-handed garage hacks like yourself
from stripping the engine cases. The
torque spec on the two drain bolts
is 14. 8 foot-pounds. I doubt that you
own a torque wrench, but they are
difficult to fit on these drain bolts in
any case. What that means is that if
you are using a wrench approximately
a foot long, you want to push on the
end of the wrench hard enough to
move a 15-pound object. That is not
very hard; I realize that it is very scary
to tighten an oil-drain bolt lightly. The
natural inclination is to tighten things
you are afraid will fall off as tight as
you can possibly get them. Don’t do
it. Use the torque spec. Now that the
bolt is rounded, you must replace it.
Torque it properly and you shouldn’t
have further problems.