Does this cylinder need replacing?

[chuck norris]

I am currently rebuilding a 024 with low compression, I know I need to replace the piston (bottom 2 pictures) but I am not sure if the cylinder needs replacing (upper 3). any opinions would be much appreciated.

[billpierce]

Hit the cylinder with some wet and dry paper see if you can get it nice and smooth again, you'd be surprised what you can get away with. As long as the nikosil out coating is ok you'll be fine. Bit hard to tell from pics.

Can't really see side of piston in pics that's the bit that will be worn. Carbon on top will clean off.

[billpierce]

Here is an ok used one and knackered one

[chuck norris]

The issue with the piston (bottom pic) is that one side is far more worn than the other, so that definitely needs to go. I will go and give the cylinder a bit of sand, then see how it looks.

[peatff]

Get some brick acid in the cylinder to fizz the aluminium off it. It might look smooth when you wet and dry it but there may be some transfer left in any grooves. I use something like 240 grit aluminium oxide paper with WD40 to clean it up and does a good job of glaze busting for the new rings to bed in.

Edited October 12, 2017 by peatff

[chuck norris]

Thanks for the reply's, but While sanding I found a considerably bigger scrape (almost 1mm deep) so I am going to replace the cylinder as well.

[bmp01]

1 hour ago, chuck norris said:

Thanks for the reply's, but While sanding I found a considerably bigger scrape (almost 1mm deep) so I am going to replace the cylinder as well.

If that's above the exhaust port, yeah not much choice. Below the exhaust port. .... you might get away with it.  What piston are you going to fit ? That will tell us how much you value the rebuild 

 

bmp01

[chuck norris]

Yeah It is above the exhaust port. I am just fitting a £40 non oem piston kit, since it will just be a backup saw.