OS 91 Surpass Piston removal
07-30-2016, 01:45 PM
#1
OS 91 Surpass Piston removal
I haven't worked on 4 cycles for over 15 years and while they are not usually difficult I have forgotten something in the dis assembly of a 91 surpass. Basically the owner passed and the engine was put away wet with the usual rust accumulation. This engine does not have the usual wrist pin removal hole in the crank case and so it presents a problem to me. I have the liner out and the wrist pin and con rod are free floating. I have tried the usual positions to lift the rod off the crank pin. I seem to remember that it was on the right side top from the rear but I have also tried the left and a few other positions. I cannot get over 1/3 off the pin and there is no maneuvering room to leverage it off. The con rod is a nice hefty piece of metal with nice bushings and I'm not about to damage them as who knows where parts are for this engine.
If you up on the procedure I'd appreciate a refresher briefing on it. You tube has yielded no help
Thanks for any help.
Dennis
If you up on the procedure I'd appreciate a refresher briefing on it. You tube has yielded no help
Thanks for any help.
Dennis
07-30-2016, 04:44 PM
#2
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If there is no wrist pin hole in the rear of the
cylinder casting, then the con rod will slide
far enough on the wrist pin to allow it to
clear the crank pin.
You just need to get the con rod to move
that far back on the wrist pin. If the wrist
pin is gunked with varnish, it will need to
be cleaned. Try filling the bottom of the piston
with straight acetone and letting it soak a
while. Then wiggle it back and forth with
acetone in it. Rubbing the pin with a pipe
cleaner soaked with acetone is helpful.
You can also try heating it, but it is difficult
because you need to wiggle it with your
fingers while it is hot, and your fingers
can get burnt. Don't get it so hot that
the varnish chars. If you do, it will become
much harder to remove.
If you can get the Teflon pad off the rear
end of the wrist pin, that will allow the pin
to move out a little and make it a little easier.
All this applies if there is rust on the wrist
pin instead of varnish, except that you will
need WD-49 instead of acetone. It will
also take a lot longer to work it off.
Jenny
cylinder casting, then the con rod will slide
far enough on the wrist pin to allow it to
clear the crank pin.
You just need to get the con rod to move
that far back on the wrist pin. If the wrist
pin is gunked with varnish, it will need to
be cleaned. Try filling the bottom of the piston
with straight acetone and letting it soak a
while. Then wiggle it back and forth with
acetone in it. Rubbing the pin with a pipe
cleaner soaked with acetone is helpful.
You can also try heating it, but it is difficult
because you need to wiggle it with your
fingers while it is hot, and your fingers
can get burnt. Don't get it so hot that
the varnish chars. If you do, it will become
much harder to remove.
If you can get the Teflon pad off the rear
end of the wrist pin, that will allow the pin
to move out a little and make it a little easier.
All this applies if there is rust on the wrist
pin instead of varnish, except that you will
need WD-49 instead of acetone. It will
also take a lot longer to work it off.
Jenny
07-31-2016, 01:42 PM
#3
Jennifer,
Thank you for your input.
I checked some info and found that it was really one of those engines that was a PITA to work on and that heat was your best friend. The owner of the engine did some serious heating on it and got the rod off. Bearings are now out and the engine can be reconditioned to new status. Thanks again.
Dennis
Thank you for your input.
I checked some info and found that it was really one of those engines that was a PITA to work on and that heat was your best friend. The owner of the engine did some serious heating on it and got the rod off. Bearings are now out and the engine can be reconditioned to new status. Thanks again.
Dennis
