can a piston be saved?

[scottsgs]

Hi all,

I got the head and cylinders off the bike. However I noticed a nick or gouge on the top edge. Is this piston ruined, or can it be saved? Also, if it is gone, can I replace just that 1 or do I have to replace all 4?

Thanks,

Scott

[dardoonk]

Can you get a picture of it? Does the gouge extend down the side into the area around the rings?

[Commodus]

So long as it doesn't interfere with the rings, I don't see why it would be a problem.

[scottsgs]

It extends just a hair over the edge toward the rings

[Nessism]

Photo would help but it doesn't sound like a problem. Just make sure the ring groove is not crushed down or otherwise compromised in that area.

[spchips]

my only concern would be the possibility of it being a potential detonation site. Be absolutely sure that you aren't running lean on that cylinder.

[Flyboy]

I agree with all said above, as long as it does not extend down to the fist ring groove, you should be fine.
What you can do to prevent detonation, and stress fractures, is to dress out any sharp burrs and edges with a fine needle file, thus releiving the stress and preventing a point where a stess fracture can start.
We do this with propellors that have picked up nicks and chips due to stones or other objects, it works great.
By dressing out all the sharp bits, you also remove any triggers for detonation.
In short....no need to junk it.
Hope that helps.

[cleonard]

Like others have said as long as the rings are not compromised you should be fine. Use a fine file or even sandpaper to get rid of any high spots. I have had to do this kind of thing a few times and never had an issue.

It's more important to be checking things like the wear on the bore/pistons, and the ring end gap.

[Nessism]

Like others have said as long as the rings are not compromised you should be fine. Use a fine file or even sandpaper to get rid of any high spots. I have had to do this kind of thing a few times and never had an issue.

It's more important to be checking things like the wear on the bore/pistons, and the ring end gap.

Agree.

Measure the cylinders for bore roundness and taper. If the service limit is reached, time for a bore job. Otherwise, new rings and a hone job are always a good idea if the engine has a fair bit of mileage - say, 20k and above.

[Steve]

Hey, now, don't let them kid you. You can save any piston for as long as you want. :shock:
Here is one that I took out of my car back in 1975.


Now back to your bike...lots of good advice given above. Remove any high or sharp edges, make sure there are no gouges in the cylinder wall. A picture would help, but based on your description, there should not be a problem. If you feel better about replacing it, you should only need the one, but it would be better to measure the cylinders to make sure they are still in good shape and not tapered due to wear. If the cylinders are looking worn, it would be better to bore them and order 4 new pistons to match.


.

[Pete Logan]

If you feel better about replacing it, you should only need the one

Yeah - cylinders don't talk to each other - each one is an individual and if it's OK, it's OK.

Replacing in sets is something dealers tell you to do - like replacing brake cylinders in sets - the damn things are designed to adjust for differences FFS. It's just a stealer money-maker.

[bwringer]

Oh, and exactly what sort of vehicle are we talking about here?

It doesn't make much difference for this particular topic unless you're trying to set a land speed record. But it's important most of the time.

All good advice so far!

[TwistedRoads]

what size engine do you have? I have 4 extra from a 650