Now, we thought that the CR was bad when
looking at the outside - what lies within our sand filled
beast...
Ummmm, crusty demons of dirt....
The first thing we did was remove the engine from
the frame - a mistake we've made before - leave the
engine in the frame and it is far easier to get the
cylinder nuts, clutch nut etc undone. But, having
removed the engine we got to see how far the sand
had progressed, as you can see from the picture it
didn't stop at the carb...
Before starting to strip the engine we drained all
the oil from the engine - noting a high metal content.
The next thing we did was remove the cylinder head,
which revealed a piston nicely seized in the barrel.
The entire motor is seized solid and nothing will
move - oh dear.
After about half an hour of heaving
and banging plus loads of WD40 we managed to get the
cylinder off, note the cack that has fallen out of the
crankcase - the piston is not being held up in this
picture it is seized in this position.
This is what happens when a small piece
of metal flies around in an engine doing 8000rpm. The
bit of metal either came from the small end bearing
or is the piston ring retaining pin. There is a nice
matching pattern on the cylinder head's squish band.
OK, so the piston won't move so we
can assume that the motor needs new bearings so we'll
have to strip the entire motor. One advantage of the
motor seizing is that it is easy to remove the primary
gear nut and the flywheel as you don't need to use any
holding tools - every cloud has a silver lining. Also,
you'll need to remove the clutch - easily done by undoing
the five bolts to remove the plates before...
Using a clutch holding tool on the
gearbox sprocket and undoing the main clutch nut and
removing the clutch basket. The clutch looks to be in
fair shape (in comparison to the rest of the bike)
Having removed the clutch we got a
good look at the bottom of the engine and the nice thick
metallic sludge in the bottom of the cases - not the
ideal environment to run a gearbox in. You'll also need
to remove the gearchange assembly before splitting the
cases.
On the other side of the engine you
will first need to remove the ignition stator using
the two allen bolts. The stator looks to be in OK condition,
and not a grain of sand to be seen.
Having removed the stator the next thing to come
off is the flywheel. We used a two legged puller which
was tightened up (make sure it is straight) and then
a blow torch was used to heat the flywheel, after
a few seconds it popped off. At this point make sure
you put the woodruff key from the crank in a safe
place.
Having removed the flywheel and the gearbox sprocket
you can now undo the cases (using an impact driver)
- Japanese bike manufacturers use the worst phillips
head bolts known to man and if you try to use a normal
screwdriver you will chew up the head in seconds and
never get them out.
Having removed all the external parts
you can separate the crankcase halves. This can be done
with a special tool (at around £150 - i.e. more
than the bike is worth, we decided not to bother) or
you can bodge up something that pulls the cases away
from the crank - you can also belt the end of the crank
with a hammer - but this will knacker the crank, so
don't do it.
Once we got it apart it became apparent
as to why the crank wouldn't move. Bearings aren't supposed
to look like this.
OK, so the bearings will have to come
out - support the crankcase between two bits of wood
(so you don't damage the crankcase faces) get a big
socket that fits the bearing and belt it with a hammer.
A few tips, heat the cases beforehand (not the bearing)
and make sure you are hitting it in the right direction,
the bearing only comes out one way!
And, here it is popped out and ready
for the bin - but don't throw it yet as it can be used
to drive the new bearing in and you can also take it
to a bearing shop and get a new one for cheaper than
a genuine Honda article.
Other horrors include the carb, which
is just plain knackered. This is the most precise part
of the engine and all the sand has combined with old
petrol and water to rot away and block all the delicate
airways and jets within the carb. Add in the fact that
the slide and top are missing and you have a good case
for a new carb.
Hmmm, this is the reed valve cage -
difficult to tell if it is going to be of any use -
the reed petals seem OK but the alloy of the cage is
very corroded and we'll have to see how it cleans up.
The costs so far...
Ripping a bike apart costs nothing
in cash terms, but can try the patience of a saint -
it only gets expensive when you lose your rag and start
breaking stuff off...
The CR125 has a sturdy looking
frame, ours seems to be in OK condition, but when you
look at it you get the impression that it isn't straight
- although it is difficult to tell as there are some
tortuous pipe bends to get the exhaust to fit snugly
on the right of the bike and the rear subframe is almost
certain to have taken a lot of punishment...we'll have
to see whether the wheels point in opposite directions...
What we
learnt this time...
You never know
what lurks under the covers. When you pay £100 for a
bike you can assume it will need some work. On the plus side
the cases are in one piece (no cracks or bits missing) and
the gearbox looks OK. On the downside the crank needs rebuilding,
the cylinder needs a rebore and new piston and the carb needs
replacing. Ho Hum, this is starting to look expensive.
