Our next letter is a little on the long side, but expresses a problem
that I am sure many of our readers have experienced when trying to
disassemble an engine for cleaning.
UI have read all of your Engine Clinic articles, starting with the first one
way back when, and also your various books on engines. I have had a
problem with an old Super Tigre . 51 BB engine, which I would like to get
your advice on. I cannot recall your ever addressing this issue, except
to mention that, on this type of engine, the wristpin must be pulled out
with a wire using a hook on the end. It would appear that this engine was
given Rislone after-run oil many years ago, as it has greenish marks. I
would guess that the engine has not been used for more than 25 years
or more. The engine was nearly stuck but would turn over. I put 3-in-1 oil
in it, and it freed up pretty well. The cylinder sleeve came out fairly easily.
Then came the problem. First, I tried using the wire to pull the pin
but could not even get the end pad out, even after heating the piston.
I inverted the engine and filled the piston cavity with WD- 40 and let it
soak overnight, with no success. I tried heating it several times—again,
no success. The rod was loose on the wristpin, so the pin had to be stuck
The 1945 Morton M- 5 was
the first radial engine to
be marketed for model
aircraft use. It weighed
only 22 ounces and
developed about 0.5hp at
3,500rpm. It was modeled
after the full-size LeBlond
engine and was developed
during World War II as a
training aid for aircraft-engine mechanics.
in the piston. I also tried your carriage bolt trick to pry the rod off the
crankpin, but there was not enough slack as it would only come about
a third off and I had to tap it back into place. I then turned to a drastic
method. I carefully drilled a hole in the front of the case at exactly the
same position as the back hole. I used a slim flat-head punch through
the front hole and carefully tried to tap the pin out, but it would not move.
I then used a press and finally got the pin to move. It took considerable
force to push the pin out of the piston. I was concerned that the pressure
used might distort the piston, but it seems to be OK. After cleaning the
piston and wristpin, they seem to have the proper slip fit, so it seems
that the pin was stuck with dried oil.
Do you think the Rislone could have possibly caused the stuck pin?
I have not encountered this problem in any of my engines that have
been stored with Rislone. Do you have any ideas as to how to remove
a wristpin that is as stuck as this one was? I would appreciate any
thoughts you have on this problem. I know you can cut the rod and get
the parts out, but with no replacement rod, that is not something to
do.—James Leisk, Shreveport, LA
Answer: Jim, I can sure relate to your wristpin experience as I have run