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A100man
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PostPosted: 16:39 - 27 Mar 2016    Post subject: Scored skirt Reply with quote

sadly not like that..

However I have hatched a plan to rejuvenate an engine. It's a 598 (58.5mm) but bores are pitted. I have cylinders from a 528 (57mm) (Yamaha xj series) that I will get bored to the correct diameter. The only slight issue is some scoring on the skirt of a piston. I have dressed it with a scothbrite and while you can see the scoring still it doesn't catch a nail and its not present above the rings..

Is this the sort of thing that ca be re-used given that the bore will be smooth?

Cheers

J

Oversize pistons are not available before anyone suggests and even if they were it would be ruiniously expensive (500 quid region)..
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Pete.
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PostPosted: 16:55 - 27 Mar 2016    Post subject: Reply with quote

If the piston is round, turn it down to an acceptable finish before boring the cylinders to suit. You might have to re-depth the ring grooves but it's unlikely if the damage is as slight as you say. You might also find that the piston is tapered so be sure to turn the appropriate taper into it.
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A100man
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PostPosted: 17:33 - 27 Mar 2016    Post subject: Reply with quote

Pete, thanks for the reply. I was hoping to just machine the bore to suit the pistons 'as is'. Not sure I can justify spending too much time/money on this. A top end gasket set and a rebore was my thinking. I can probably buy some better pistons though..

here's what I have

https://lh3.googleusercontent.com/-D2IQfwm640U/VvgW9V_h4BI/AAAAAAAAAWA/KKeBY-nFDP0wSUkwh_GkGXCZ2Y0lX9VsACCo/s576-Ic42/20160327_181439.jpg


Bugger -why can't I post pics..?

*Because your link was to a webpage, not an image. An image link will end in the extension .jpg, .png, .gif.

From the page you linked to. Right click on the image and select "copy image URL". Paste that into your post and wrap it in image tags like you did.

One slight further complication with google images, you need to remove the 's" from the 'https://' - stinkwheel
*
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stinkwheel
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Joined: 12 Jul 2004
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PostPosted: 11:11 - 28 Mar 2016    Post subject: Reply with quote

On a more relevant note. That scoring seems very light indeed. I wouldn't worry about it.

At the end of the day, what does the piston skirt actually do? In the normal scheme of things, nothing.
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weasley
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PostPosted: 11:22 - 28 Mar 2016    Post subject: Reply with quote

stinkwheel wrote:
On a more relevant note. That scoring seems very light indeed. I wouldn't worry about it.

At the end of the day, what does the piston skirt actually do? In the normal scheme of things, nothing.


Agreed. I wouldn't call that scored, just some running marks. If you can't feel them with a fingernail then by all means give them a light polish, but I'd say it's good to go.

The skirt is mostly to keep the piston from canting. I've seen some F1 engine pistons with virtually no skirt.
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A100man
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PostPosted: 12:21 - 28 Mar 2016    Post subject: Reply with quote

Thank S-W, and W -on both counts - what I was hoping to hear.
In all probabily the scoring happened during the removal/ unsiezing of a pitted/rusty bore..

Cheers

J
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