Mitaka piston rings

[kiwisteve74]

Hi guys, I posted this on my build thread in the project section but it was getting little traffic and no quick answer from the knowledgable lads on the forum.

I ordered my Pistons from PJME in the UK, which with shipping to New Zealand were the cheapest of the 3 places I tried. I gave them measurements of my bore and they asked me what was stamped on the cylinder. They told me that my "B" stamped cylinders will need 55.96 Piston kits which they promptly sent out. I've just now tried fitting one to the cylinder and after working out which ring was which I found that the top ring fits nicely as you would expect but there is no way the bottom one is going in with the expander ring in place. The bottom ring ends don't even get close to the pin and won't compress enough to slide the cylinder on. If I take the expander ring out its seems fine.

Do I need it? What's the go here?

[James P]

Is the bottom ring on these pistons of keystone section? If so, have you got the bottom ring upside-down?

Sometimes the bottom ring is narrower to allow for the expander - is it possible you have the top and bottom rings mixed up?

Regards,
James

[mellorp]

As James says, you might have the rings the wrong way round/upside down. Try them every which way. The expander ring is there for a reason

Simple but general info here