Share cool pics. (Factory piston markings ) ?

[vedgar]

After removing the head on my 80SG , I noticed the #50 marked on the crown of the pistons. Anyone know what the number means, weight , diameter, piston clearance .50 mm maybe ? The bike has only a couple thousand miles so the markings have not been eradicated yet. File this one under Hmmmmm. Just thought I would share another piece of xs1100 history.
Vance

[natemoen]

Don't know what the numbers mean but mine all had markings like that on all my pistons.

[vedgar]

the quest begins

Time to try and find out !

[Cuda 69]

just curious, if the engine only has a few k's on it, then why are you removing heads?

[vedgar]

No compression cylinder 4

Bought it from the original owner, who said he quit riding it around 1982. He gave up on returning it to the road. I have no idea how the valve was bent as it was in time (cam to crank) . Fix it and move on as they say.
Vance

[Cuda 69]

ah, ok, thanks, good luck with the build.

[Dan Hodges]

After removing the head on my 80SG , I noticed the #50 marked on the crown of the pistons. Anyone know what the number means, weight , diameter, piston clearance .50 mm maybe ? The bike has only a couple thousand miles so the markings have not been eradicated yet. File this one under Hmmmmm. Just thought I would share another piece of xs1100 history.
Vance

A stock 80-82 piston will have the factory part number and an arrow on the top of the piston from the factory.
The #50 on your piston has been inscribed after the motor was apart or is/was a replacement piston. It also suggest that the motor hasn't been run but very little otherwise the etching would have burned off.

I purchase my XS new in the crate and it no such markings when I finally took it apart and over the years I've seen scads of XS pistons and none had such markings however it isn't unusual for people to mark things like pistons with numbers when they have a motor disasembled.

I personally stamp mine and number them when I build a motor but unless it's stamped or cast/made in the piston it will burn off in a short period of time.

[vedgar]

piston markings.

All four pistons have the same marking, a # 50 on them. the original owner assured me , the motor was never apart. Memories get foggy who knows what the truth is. I appreciate the feedback. I just got the new pilot jets in the mail (Mikuni originals) and should be up and running again by Monday. I have bought and sold hundreds of cars and bikes and believe I can,t be fooled by a shady story and owner. The bike looks feels and smells to be a true low mileage bike. I am probably not as sharp as I think I am if this guy tripped me up. Original tires still have a little of the red stripe in the tread grooves.
Vance

[Eveready1100]

Easiest way to find out what they mean is to measure the bore. That'll tell you what's going on.
Definitely looks like just a white maker pen was used for that, commonly used in workshops and bike breakers to identify parts. Wouldn't have lasted more that a couple of minutes running.
Maybe a big bore gone wrong??

[trbig]

I've also seen that white marking on pistons that have been run a long time and partially covered with carbon. That marker, whatever it was, doesn't burn off very well at all.

Can't answer WHY it was there, but as stated, I really doubt those marks came from the factory. The old man might have had someone look into it way back and forgot about it. He may not have purposely lied to you... just didn't remember.