IAME X30 piston change & hone

I’m new to the X30 engines and was wondering, is it mandatory to hone the cylinder every time when piston is changed? Some people claim it needs to be changed every race, some say every two races and the rest seem to follow the manufacturer recommendation of running hours.

Hi Daniel

What I found is unless you’re chasing thousandths there’s no need to hone the cylinder every time, no. And no need to change the piston every race.

Hours wise I’m comfortable running 15 hours on a piston, but I pull the head off at 10 hours and clean/inspect the piston face with a magnifier - looking for hairline cracks developing. I’ve never found any.

At 30 hours do a top and bottom including a cylinder hone at the shop.

In my experience hone after every piston change is the best for reliability and performance.

A hone doesn’t cost much. But if you don’t want to you could look after the crosshatches. They should be visible and not look polished.

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Lucas, what’s the purpose of the crosshatching in the cylinder? Is it to allow the piston to move freely? Without crosshatching it can create suction or something?

Crosshatches are there for making the oil stick to the walls

Aha so it helps with lubricating the piston movement.

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Yea, also aid breaking in of the ring to make a better seal and therefore more compression

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only adding that “honing” is a broad spectrum, doesn’t mean that every time you have to take off a ton of material or give up piston sizes. A good shop will inspect the cylinder, measure it and if needed the hone can be a light refresh to re-establish the cross-hatching that has become light (barely any material removed) to a deeper straightening/damage fix that will eat up few piston sizes, depending on condition. It’s performance and reliability too

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Thanks for the replies!

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so educational to read from andy always . many thanks

There is actually even more to it…

Specification and Measurement of Plateau Honed Surfaces

This all just as valid for cast iron liner 2 strokes…perhaps more so…as we have a lot LESS oil to work with. Oil is sticky, and likes to lodge in crevices…so having a LOT of deep valleys to hold oil AND a smooth plateau (what they are now calling an “extreme plateau”) seems like it would be the ticket for CI two strokes.

For Nikasil lined cylinders, it may be different…gliding on Silicon Carbide bits…

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Aha! Thank you for link.

Hone surface is super interesting. Lake Speed Jr. has some great videos on it. Here’s one. A long one.

I like reading nerdy wrench stuff, thanks! It’s good to have some understanding although I’ll never put it to use.