What has happened to this piston?

[scooty]

I've seen damage like that before caused by a ring peg coming out. Are both the pegs still in Scotty?

Definately a spun ring. Either the ring has jumped over the peg pushing it back or the peg has fell out.

Hi Al and Jims
managed to free top ring and yes ring peg has gone

possible race-tour piston fault? anyone else had a problem with them?
see also
http://scooterotica.org/forum/viewtopic.php?f=7&t=11215

[Knowledge]

"Mag" on the LCGB forum has posted a photo of his exhaust port, and it looks just like your photo.

I suspect he will find something amiss with his piston when he has a good look at it.

[goldeneye]

yes

[Bufficus]

I've seen damage like that before caused by a ring peg coming out. Are both the pegs still in Scotty?

Definately a spun ring. Either the ring has jumped over the peg pushing it back or the peg has fell out.

Hi Al and Jims
managed to free top ring and yes ring peg has gone

possible race-tour piston fault? anyone else had a problem with them?
see also
http://scooterotica.org/forum/viewtopic.php?f=7&t=11215

Yes. As posted on another thread.



I've had a Race Tour piston top ring issue lately. A 2K mile piston top ring peg wore or dropped to 0.5mm. Not enough to stop the top ring spinning. Luckily I noticed this after an annual check and rebuild.

I was not impressed after only 2K. MB replaced the piston at cost + discount. I expected a replacement.

I accepted because of limited options. Having spoken to others I know this is not uncommon.

PS. My piston had not been getting hot. As verified by the underside of the piston.
Also, I'm not blaming anyone, just want to know what's happening.

[ScooterLoopyJohn]

I have used MB pistons in many set ups and after running well for 2000 miles the performance seemed off, so i striped and found nearlly all had the bottom ring stuck in the groove. changed the rings and had to open out the lower groove to get the new ring in. This is annoying thing to happen to such a high cost item. All ran well after reringing tho. Pos fault ?

[soullad]

is this also a racetour piston?
http://scooterotica.org/forum/viewtopic.php?f=7&t=11215

[adriang]

any chance of a pic of the underside of the crown?

Why did you want to see the under side?

This thread is very much an education for me, but was very curious about this..

[soullad]

any chance of a pic of the underside of the crown?

Why did you want to see the under side?

This thread is very much an education for me, but was very curious about this..

It can give a good indication of whether the piston was running hot or not, although in this instance I couldn't see anything to suggest this.

[scooty]

is this also a racetour piston?
http://scooterotica.org/forum/viewtopic.php?f=7&t=11215

also race-tour i believe

[J1MS]

Pencil marks in line with ring pegs helps align the piston rings on assembly.
If piston rings are accidentally pushed against the pegs on assembly the pegs can be loosened even if the piston dosnt fully slide into the barrel.
They are an interferance fit so any undue pressure can efffect their later performance.