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MG Midget and Sprite Technical - Cylinder Honing and Piston Rings

After a quick bit of advice, as always! :-)

As you probably know, my engine is in bits. Block is completely stripped, pistons and rods out etc.

There was no problem with the rings and bores prior to dismantling. Only about 10 - 12k since the engine was re-bored and rings replaced. Engine is apart for other reasons.

But once things are apart, will the pistons and rings go back together and seal OK in the bores? Or should I give the cylinders a light hone and/or replace the rings?

Pistons will go back into the same bores they came from. I am not into replacing things for the sake of it.

Thanks,
Malc.
Malcolm

Low miles, so should be OK to put everything back where it came from.
David Smith

If I hadn't read David's answer, and I am certain that he knows better than me, I would have said to just scuff the bores lightly with a bit of wet & dry to clear any potential glaze. Then rinse down and resassemble. Even if parts go back in their original homes there is potential for rings to move a little and make fresh contact points.
GuyW

I thought rings were liable to rotate in use.
Dave O'Neill 2

I've seen some with little pegs to stop them and keep the gaps offset. Can't remember what engine though!
GuyW

Guy,

That would normally be a 2 stroke as you wouldn't want the ring ends passing a port.
David Billington

Yes true indeed. But it's a long time since I worked on a 2 stroke!

My choice would still be to scuff the notes lightly to break up any glaze.
GuyW

Malc. Assemble the cleaned rings into the cleaned and lightly oiled bores.

I would be interested in knowing if you still have the honing in the bores from the first build up? If not, what type of oil have you been using? I have seen honing marks still existing on engines having about 100K miles due to the high quality oils being used since the mid-late 1970s. So, less than 10K miles may not even be truly broken in.

Les
Les Bengtson

I wouldn't. I'd put it back as is, with the same rings, and rings do rotate.

If the engine has only 12k on it, and you didn't already have it apart for reasons other than bore/pistons/rings related, would you pull it apart to hone the bores? Answer no. So why now?

Why won't the rings seal just because the pistons have been taken out? They'll seal as well as they were sealing before, as long as you don't break them putting the pistons back in.

If it was 50k miles, I'd re-ring and shell it. But for 12k miles I don't see the need, it's barely run in. But if you do put new rings in, then it might benefit from a light glaze bust, to help the new rings bed in.

anamnesis

Cool, I will go for the chuck it back together option then. No need to spend more £££.

Thanks for the advice everyone. It's not my day job so I forget the details on what is best practice on such things.

Happy Spridgeting!
Malc
Malcolm

This thread was discussed between 25/01/2021 and 26/01/2021

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