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Dent on piston
voucht - 15/2/20 at 03:34 PM

Hello again,

When I bought some pistons on ebay (uk!) a few months ago, two of them had a very small dent. At the time, I thought it wouldn’t be an issue, so I didn’t send them back. My mistake.

Here are some pictures:

Piston1

Top view: you barely can see the dent
Description
Description
Side view: here you go
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Description

Piston2

Description
Description
Description
Description


The dents are very small, just a few mm, and nothing is sticking out from the cylindrical face. At the finger tip touch, the dents are smooth and seem to be only "inwards" or "concave".

Do you think it would be a problem to use them ?

It is for a Kawasaki ZX550 from 1984 I’m renovating. I don’t want to spend too much money on it, and I already have! New pistons are no longer available from Kawasaki. I found only one new piston on ebay, for 65€ (!), and second hands are not common and when available, still pretty expensive, and you can never be sure they will be in perfect condition (like it happened to me when I bought these ones from ebay uk). As I already need to spend 130€ for 4 sets of piston rings, I’d like to avoid buying two other pistons. But I don’t want to irreversibly damage the cylinders either.

What do you guys think? Can I use them?

Thanks!

nick205 - 15/2/20 at 07:01 PM

I'd speak to an engine reconditioning company for their opinion. They will probably want to see the Pistons to be able to advise you. They may be able to "dress" the tops of the Pistons to improve them if it is required.

jacko - 15/2/20 at 09:36 PM

Would this have anything to do with the stuck piston ring you where asking about in another post ? If so the piston could be damage more then you think
Jacko

Theshed - 15/2/20 at 11:34 PM

Looks minor to me but there will be a burr, top and side. That is inevitable. A careful use of a fine file will remove that leaving plenty of undamaged surface above the top ring.

steve m - 16/2/20 at 09:08 AM

I would file / emery paper any rough bits down, thoroughly wash them, and use

steve

voucht - 16/2/20 at 11:14 AM

quote:
Originally posted by jacko
Would this have anything to do with the stuck piston ring you where asking about in another post ? If so the piston could be damage more then you think.
Jacko


These 2 pistons are from a set of 3 I bought second hand several months ago, because the original pistons from the engine didn't look good, except for one of them. The piston with the stuck ring I was asking about in another post was one of these original pistons. I tried to remove the ring to use it in place of one of the two "new ones" with dents (this post). But it is in a too bad condition to be used, so I discarded it.
Which left me with: one of the original piston which is in perfect condition, one from the set of 3 I bought one ebay which is in perfect condition, and two from the same set of 3, which are in perfect condition too, except for these small dents.

voucht - 16/2/20 at 11:18 AM

Thank you very much for the answers.

I will give a go at the file / emery paper.

Thanks.

jacko - 16/2/20 at 11:48 AM

Hi thankyou for the info about the Pistons .
one thing you will have to mind if your mix and matching the Pistons are all the same weight and balanced
Good luck with your build
Jacko

Angel Acevedo - 16/2/20 at 02:08 PM

quote:
Originally posted by voucht
Thank you very much for the answers.

I will give a go at the file / emery paper.

Thanks.


Once you are done, remove any sharp edges as sharp edges on combustion chambers get very hot and may lead to detonation (Preignition?).
Although I don´t know if piston material would. But I´d do it for peace of mind.

Mr Whippy - 17/2/20 at 07:14 AM

looks like it's been dropped on the floor

40inches - 17/2/20 at 09:40 AM

quote:
Originally posted by Mr Whippy
looks like it's been dropped on the floor

That was my thought.

nick205 - 17/2/20 at 10:44 AM

quote:
Originally posted by Mr Whippy
looks like it's been dropped on the floor


Seeing them now on a larger screen (was looking on my phone before) I feel the same. I'd still be wary of more damage than is immediately obvious and seek input from an engine rebuild company. If they're been dropped and dented then there's a chance they may be out of round and cause damage to cylinder bores on a re-assembled engine. It could also be an indication why the piston rings are stuck.