[Shotimes] timing sprockets not fitting crank

[George Fourchy]

On Sat, 03 Sep 2005 21:11:15 -0400, Robert Bruce wrote:

>As I recall, the key
>fits either direction and the timing belt gear should be installed with the
>timing mark facing away from the block.

The key presses into the slot in the crankshaft facing either way.  It is an
interference fit.  You might need to tap the key down at one end or another with a
small ball peen hammer to make sure it is parallel with the crankshaft.  It can be
tapped down at one end, which will slide it in the slot and raise the other end, or
vice versa.  The sprocket should ideally slide over the key and into place on the
crank...the rounded inner edge of the hole in the sprocket matches the curved
portion of the base of the nose/snout of the crank, so that it will fit snug against
the end of the #1 crank journal.  It might see some resistance as it goes over the
key....this is normal.  It doesn't take too much mushrooming of the top of the key
from hammering it to make the sprocket hard to slide over it.  If this happens,
clean it up with a small file or emery paper.  You might want to use a plastic
hammer.

I have found that in ATX engines, the damper does not need to be pulled (with a
puller) off the crank (will slide easily, but with no slop), and will slide onto it
at reassembly, with a gentle tap or two of a hammer on a block, so that there is no
drawdown necessary by the crank bolt.  I sure wish MTX engines were that way...I
have no idea why they are different.  I found one MTX engine I did the crank cancer
surgery on where the crankshaft snout was so distorted, due to hammering by a
previous clutz that was trying to change the belt, that  1). it ruined my damper
puller getting the damper off...it twisted into a pretzel.  2). I had to file a
BUNCH of metal off the snout to get both the crank sprocket and the damper (one he
borrowed from me) to go on again.  The original damper was toast...it was smashed so
bad it wouldn't go on all the way, which was what caused his cancer.  The ballooning
of the snout was clearly visible without measuring it.  This might be the problem
with the engine in question.  In the past, someone may have hammered on the damper
trying to get it on, which mushroomed the crankshaft.  The metal it is made of isn't
THAT hard.  The engine I was working on went together with no problem after I filed
down the snout so that the damper and sprocket would slide on.

If the damper and sprocket go on part way then stop, the crank is definitely
mushroomed.  DO NOT hammer the damper on if this is the case....it should move 1/4
of an inch or so with each soft tap of the hammer.  There will be a soft thud from
the crank as it moves....the whole thing rings like a bell when the damper is in
place...if it rings sooner than that, the snout is ballooned.  Remove the key and
file the snout down at the high point, with a fine toothed metal file, trying as
much as possible to hit all sides evenly.  When you get all the way around the snout
with the file on the first revolution, try the parts.  It doesn't need to be exactly
round, as long as the sprocket doesn't wobble TOO much....if it will just slide into
place and not twich back and forth when you try to twist it, it will work...the
damper bolt holds it in place.  Make SURE you torque it to the right amount.  If it
makes you nervous because it seems to be loose, use some red locktite.  Change the
seal, and you'll never have to take that sprocket off again.  Lowrider is evidence
of that.  It can be a few thousandths of an inch out of round...Lowrider is, due to
the less than perfect placement of the shims I stuck under the sprocket into the
worn part of the crank.

The engine I used the file on is running fine now, 4 years later....and
Lowrider....it went another 93K miles after that fix, and it was finally parked by
something totally different.

George