Piston Install Help X30

Hello All,

I’m trying to install my first piston and I’m having a lot of trouble. I got the piston on the con rod and the circlips in. The trouble I’m having is with the piston Ring. For the life of me I cannot get the piston with the ring into the cylinder. It slides in fine with out the ring, but it won’t get past the start of the cylinder when I put the ring on. I tried for a solid 20 Minutes but to no avail, I squeezed the ring with my hand and made sure it was the right way up as well as facing the right direction. The piston is the correct size and the cylinder is not warped.

Am I doing something wrong?

Thank you!

Are you lining the gap in the ring with the nodule in the piston? Once you’ve done that, you should be able to keep the ring compressed by hand and gently place the cylinder onto it.

Also, while I think of it. have you checked the ring gap?

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What James said. Look closely into the piston ring groove you’ll see a small nodule, the gap in the ring must be there otherwise you’ll never get it into the cylinder.

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Definitely worth checking this too. You do this by inserting the ring into the cylinder without the piston, then use the piston to square it up in the bore and measure the gap in the ring. If its too tight, it will be difficult or impossible to install on the piston.

Not sure what the gap should be. Maybe someone else can chime in with some numbers?

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0.3mm per iames overhaul manual :raised_hands:t2:


Thanks everyone for the responses, how would I go about reducing the piston ring gap. Surely I cannot just bend it closer with my hands. What is the correct way to close the gap in the ring?

Correct method is to use a ring grinder that files the ring down totally straight.

But a fine file do the job too, just sand down the rough edges when you are finished.

On my Kz I set the file in a vise straight and then file the ring in a up and down motion. Little at the time and measure a lot of times :+1:t2:


I just had to line it up with the nodule, thank you all so much for your help!



The ring gap is checked with a feeler blade with the ring removed from the piston and placed in the bore.

I usually put the ring in/down the cylinder a few mm by hand, then use the piston to push it up to ensure its square to the bore.

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Thank you! I am familiar with checking the ring gap, I got myself a set of quality feeler gauges.

Going to also get a ring grinder to file it down in the future if needed.

Thanks again to everyone who helped.


Glad you did it without knocking off one of the cylinder bore tangs……….unlike me first time I did it :roll_eyes::joy::joy:

That was one expensive piston :sweat_smile::sweat_smile: