missing ring locating pin

[MrTwoJay]

After splitting cases to repair leak between cranc case and gearbox, I noticed that one of the ring locating pins are missing on the piston, it seems to have made its way out the exhaust port.

My question is, would it be ok to run the motor with the missing pin, or could it cause the ring to get stuck in a port?
It seems to have been running like this for a while now.

 

[Larry's Shee]

Only luck has kept the ring end from dropping into the exhaust port and causing catastrofic engine failure.

You're sure the pin is gone?

The engine will run without that ring.

Best way would be have the bore measured and if wear is minimal, get a new piston.
If not, time for fresh bore.

 

[MrTwoJay]

Ok, update time:
After close inspection, I did find a locating pin, but for some reason the ring turns around (yes when closed), seems to be too located too low, or worn...
The piston doesnt look tooo bad, but there is a bit of wear and movement (rocking).
Checked the bore and it looks spot on, it is bored 2nd oversize.

Did think about removing the bottom(problem) ring, as there are aftermarket pistons available that only have one ring, but Im starting to think a new piston and hone might be the best route.
Have to wait until monday to get price and availability from the stealers...

I now saw that the crank thread is also damaged on the flywheel side, looks like somene struggled to remove the flywheel and pulled the threads a bit, nut turns on very tight and there some distortion in the threads(looks like it was over torqued).
Did some measurements and with a new nut and doing away with the fat washer/spacer, I might get away with enough thread. It still does tighten up though, but I doubt I would be able to torque it correctly or it might come loose at the wrong time, causing more damage.
The further I dig, the more problems im finding.

 

[Blaaster]

The ring locating pin must be there to stop ring migration to a port.

If the rings rock, it means that the lands are worn and may be prone to cracking.

Forget about the idea of a one ringed piston, or removing a ring.

The fat washer must be there and if the nut cannot be tightened up to 53 ft lbs there is a major possibility that the flywheel will spin.

Measure the bore and if within specs, fit a new piston, if any doubts have a re-bore done.