Damaged piston

[allan.walker]

Please don't shoot me down in flames, but would it be safe to use this piston in a Square Four? The missing piece is on the main thrust face (where the arrow on the crown points.) The piston had been in use for a very low mileage in another engine and is otherwise sound.
Would that amount missing lead to any running problems?

[Roger Gwynn]

I would be happy to use it, the loss amounts to a small percentage of the thrust face.

[allan.walker]

Thanks, Roger.
There is a question as to how the damage occurred. I don't know if the engine it was in had stopped with a bang, or whether the piston was originally fitted with a piece missing.
My concern is, why would someone do that? I follow your logic about it only being a relatively small piece, but if I were to re-use it, I would definitely smooth-off the ragged edges first.
Hmm....

[JohnnyBeckett]

hi , have you found the broken bit and is it one bit , the piston may have been dropped or deranged before it was fitted i would still use the piston

i would just take the sharp edges off where it is broken

[allan.walker]

The piston came to me in the condition shown, so I don't know what the 'shrapnel' may have looked like.
That's two replies in favour, any against?

[paul.jameson]

If you plan on fitting a double adult sidecar to the Square and then taking wife and 2 teenage kids down the motorway system to the south of Italy on holiday then I would advise against. Otherwise, I can't see too much of a problem. But what oversize is it? One of us might well have a more complete used piston sitting on the shelf (or more likely 4 of them).

[Paul_Linden]

It may be worth doing a dye test on it to see if there are any cracks.

[nevhunter]

It''s probably rolled off a bench onto a concrete floor. That's a "W" slot type piston for touring which sometimes cracks near the lower end of the slot after a long mileage. Just have a good look around and reinstall it. I won't tell anyone IF you don't. The bottom edge is only loaded if the Piston is very loose. It's not a particularly short skirt piston. Nev

[allan.walker]

Thanks for all the replies.
The general consensus seems to be that it should be ok. Crack testing using dye sounds like a good idea. The pistons are +40 thou, if anyone has one...
I'll have a good think.