AM piston broke...

[calereeves]

I can't find the brand of this one, but I'm thinking it was golf. One of the first saws I put back together and it came back to me with the piston and rings in pieces. Think it was a casting problem with the piston, or a problem with the rings? Toasted the OEM cylinder too. Not too long after I finished this one, I heeded the advice of many and started using oem or meteor/caber only.

Any guesses on what went wrong?

 

[Nate66n1]

That hurts, looks like it definitely took a good shot to break the crown and first ring land like that

 

[RiverRat2]

Had you ported the topend?

 

[calereeves]

No, oem cylinder was in good shape to start with. Bearings are all good. Piston and rings were new.

 

[Brushwacker]

I can't find the brand of this one, but I'm thinking it was golf. One of the first saws I put back together and it came back to me with the piston and rings in pieces. Think it was a casting problem with the piston, or a problem with the rings? Toasted the OEM cylinder too. Not too long after I finished this one, I heeded the advice of many and started using oem or meteor/caber only.

Any guesses on what went wrong?

Not an expert, but doesn't the color indicate heat on the lower part ? May be that put the squeeze on the lower ring until it broke and caused the damage above ? Inadequate lubricant, straight gas or contaminated gas may be or just to lean of a setting, lean and high RPM's ?

 

[Spokerider]

Yep, all bets are off with AM stuff. Unknown metallurgy and ? porosity in the casting.

 

[SS Sniper]

Yep, all bets are off with AM stuff. Unknown metallurgy and ? porosity in the casting.

I agree.

 

[Mad Professor]

What do top of port look like where rings/piston broke? Maybe caught a ring in a port?

 

[tree monkey]

need a pic of the top of the piston

 

[nmurph]

455/460?

 

[calereeves]

It's from a 261.

 

[calereeves]

Piston

 

[calereeves]

Cylinder. It's tough to see in the pics but chunks of piston and/or ring chewed up the edges of the transfers. I think this would be a perfect porting cylinder since the edges of all of the ports would be ground on, but it's out of my league for saving.

 

[calereeves]

Any more guesses what caused it to fail?

 

[watsonr]

what was the skirt thickness?

 

[pioneerguy600]

The ring caught on the downstroke, heat swelled?

 

[nmurph]

The ring caught on the downstroke, heat swelled?

I'm thinking the ring end gap may have been too small?????

 

[kyle.kipple]

I put a golf piston into a 660 once. Started it, left on fast for 3 seconds, blipped to 3/4 and that's all she wrote. I hope I can find it to take a picture because the damage is near identical to yours shown.

 

[pioneerguy600]

I'm thinking the ring end gap may have been too small?????

Me to, I think the ring got too hot and swelled out into the exhaust port.

 

[CR888]

Sometimes AM parts are great and the only feasable way to keep a saw in service, somtimes am parts cost you more than you save if something goes boom!! l am not sure what caused this but check your muffler.....it might rattle if you shake it. You don't want to store parts in the muffler....its can be pricey too.lol