Compression : Cylinder & Bore

My Villiers Mk15 was down on compression so I tried the trick of raising the piston ¾ up and poured petrol in the top of the bore to see if it leaked into the sump.  It did, not fast but it did.  So, I took the thing apart and could see the following condition of the bore and piston.





I'd be grateful of anyone's opinion as to what you see here.  Are these usable or to far scored.  I notice a ridge at the bottom of the bore that would indicate to me that this is to bottom of the piston's travel therefore indicating excessive ware on the bore.

Any thoughts would be much appreciated.

Many thanks

Reach.

Hard to tell in the photos but the bore doesn't too bad, is there much of a lip at the top? I think the piston will always score worse because it's made of (relatively) soft alloy.

TBH, if it were mine I think I would just clean up/deglaze the bore with the flap wheel, clean up the piston with some fine emery cloth or wet and dry paper and WD-40 and fit new rings.

The piston sits in a bore several thou larger, the design of the rings also isn't a tight fit so putting petrol above the piston its bound to leak into the sump, have you checked the valves, that's where the compression is likely to go

Maryalice

Hi Maryalice,

Thanks for the info.. yes, one of the values was slightly pourious during the 'petrol' test so that is marked for re-seeting. Thanks for the info about the 'petrol tick' good to know.

Hi Mattblack,

Thank you for your thoughts. I will probally go with your advice as well as re-seet the offending value. I'll wait a couple of days to allow some others to comment though.

Took the liberty of moving the topic to a more appropriate section.
As per maryalice, re-seating valves seats is a good place to start. L&S Engineers have valves.

Have you tried gapping the rings in the bore?

Just had another look at the pictures, if the rings haven't been moved after the piston was removed the gaps are all lined up...