This is tricky at best and you must be sure to inspect the
vehicle to make certain that there are no suprises later on
when you are paying for the certification. I have a sheet that
I use to go over the bike in an orderly fashion and that way I
don't miss anything important. Prices of motorcycles have risen
with demand and replacement parts are more expensive than ever
before so be careful when adding up the parts you may need to
purchase.
Brakes...disc
You have to be careful when checking disc brakes. There
is the brake fluid to inspect. Pad wear must be
addressed. The condition of the rotor itself has to be looked
at. These are very expensive to replace and they do wear. Feel
the edge and if there is a ridge at the outer edge then they
have worn. If the lever comes into the bar when the brakes are
applied then it may be rotor time :( The only way to really
tell is with the specs and a vernier. When looking at a
potential purchase you probably won't be able to check and
measure everything so see if the brake lever can be pulled into
the handlebar. Check for brake fluid leakage from the area of
the master cylinder.
The pads can be inspected by looking at the caliper from the
front, looking up. A brake pad should be on either side of the
brake rotor. Sometimes there is a red wear line you can see.
Having a small flashlight will really help out here. There
should, of course, be pad material on the pad. If it has worn
to metal then the disc will have a rough finish and be burnt
looking.
Brakes...Drum
You won't find many street bikes that have drum brakes
on the front wheel, they are still to be found as the rear
brake on some models. They are usually mechanically operated,
activated by a foot lever located near the right side footrest.
At the rear wheel there may be an indicator close to the
actuator cam shaft, but that is a rough guide at best. To
really inspect the remaining brake shoe life you must take the
wheel off the bike.
Some off road or enduro style bikes may have cable activated
front brakes and the thing to look for here is a siezed cable
(it will cause the brakes to stay engaged...not good) also,
there will be cable adjusters, that compensate for cable
stretch, make sure that these are not all the way out, thus
indicating that the cable is totaly stretched.
Brake Calipers
In the caliper a piston is activated by you when you
pull the front brake lever. It pushes against the actual brake
pads to apply pressure on the disc. One or several (depending
on make) "rubber" o-rings seal the fluid from escaping between
the piston and wall of the caliper. These rings serve another
function and that is to return the piston to its original
position (brakes off) These rings are the only thing
returning this piston and when there is corrosion, the piston
can be forced on because the hydraulic pressure is great enough
to do so, however there is no (hydraulic) help for the piston
to return and thus causes the brakes to be applied even though
we are not pulling the lever. The resulting application of the
brakes causes a heat build up, brake fluid expands (due to
heat) thus forcing the brakes on even more. This is not a good
situation to be in as a motorcyclist
I've seen bikes pull into the shop with the rear disc brake so
hot that it is glowing cherry red with heat build up. The brake
pads were totally worn away and the repair parts this bike
would need include caliper assembly, disc brake rotor, wheel
bearings and all dust seals. Expensive!!!
How If They Are Seized?
Elevate the wheel in question and spin it. Apply the
brake to that wheel and release the brake. Does the wheel spin
now? Is it a little harder to spin than it was before you
applied the brake?
Previous experience plays a large part of what you do next
because all disc brakes "drag" a little and that must not be
mistaken for seized brakes. To tell whether the brakes are
truly seized, hit the caliper with a "dead blow" hammer (soft
mallet, so as not to mark the caliper) If the wheel spins with
less drag than before, then the brakes are sticking on and must
be repaired.
When you are riding the bike pull in the clutch and coast every
once in awhile. Does the bike slow down too quickly? Does
everything sound OK?
Catch it early and you will save yourself expensive repairs.
Front Forks
The forks are a very important part of the bike as they provide
the front suspension of the vehicle. Having oil as the damping
agent means that there is an oil seal to keep it contained. One
per fork and if these start to leak the oil will be all over
your brakes and pants and not in the fork to help dampen the
load. This can cause handling problems as well as ruin a set or
two of brake pads. There is a tell tail ring of oil around the
fork tube so rock the (parked) bike a few times, with the front
brake on and then inspect the fork tube...any oil???
The forks can also be bent and a slight bend is hard to
spot. Look at the forks from the side, line up both forks
visually...are they in line with one another? If not, they are
bent or twisted in the crowns meaning the front end has
impacted with something.
Also the forks may be damaged by pitting or rust and the
chrome coating may have started to lift meaning that the rubber
fork seal will get ripped every time that it passes the damaged
area. These can be expensive to purchase.
Handlebars
Older bikes have one piece handlebars, newer styles have
two, each one is slipped over the fork tube. The difference is
style and price. The older style bar is by far a lot cheaper to
replace than the newer style. They should not be bent. If they
are, then it tells you the bike has fallen. The throttle side
is the more important of the two because if it bends then the
bend can sieze the throttle tube which spins on top of the
bar.
You should not bend them back to shape...here's why. On
the first bend the outside of the actual bend (of the bar) is
stretched and weakened. Not good...but possibly still drivable.
If you bend it back then you now stretch the opposite side (of
the bend) and weaken it even more...possibly to the point it
may break while driving.
Shocks
The front suspension we have covered and
the same theory applies to the rear suspension. There are two
types...Dual shocks and Monoshock...
Monoshocks are not as easy to spot because they are tucked
away in the guts of the bike. Look in front of the rear wheel
and there should be a tube like cylinder running up to just
under the front of the seat. It may be shrouded and all you can
do would be to look for oil leakage in the area. The best test
is to bounce the suspension and see how it reacts.
Dual shock types of suspension are totally visable and there
will be one on each side of the bike, attaching the rear of the
swingarm to the rear area of the frame, usually near the back
of the seat. They should be straight, no oil leakage is
supposted to be there. Once again the best test is to bounce
the suspension and see how it reacts. (I will add to this in
the near future :)