Alignment Pins . . . what are they and why should I care?
Topic: Alignment pins - why are they important?
What are they?: They are small pins made of hardened steel. Their purpose is to keep the crankshaft bearings from rotating in their saddles.
- It's starting to get a little twist - which causes the bearing to vibrate - shaking the pins out. If you see signs of brinelling in the bearing saddles it's time for a rebuild
- Usually the lower bearing loses it's pin first.
- Most of the time the pin just blows through the crankcase, up the ports, through the combustion chamber and out the exhaust.
- Sometimes it'll get wedged in the slot on the lower end of the connecting rod
- Sometimes it gets caught in the port window when the piston goes up - causing damage to the edge of the piston
- Most of the time you can see pieces embedded in the surface of the combustion chamber and/or the top of the piston
Should I care?: Only if your motor was damaged (piston or bore dmage) or you plan to rebuild your crankshaft. If you have a 1990 or newer motor, it's been my experience that these motors are the worst for throwing the pins out. How bad can it get? Have a look:
Copyright 2012 Capt'n Obveeus