Retroarms gearbox and cylinder

I have a RA gearbox, cylinder, and cylinder head, and the cylinder doesn’t appear to fit snug into the gearbox, so much so that the sector gear hits the last 2mm of the cylinder. Am I meant to trim the cylinder down or do I push it further over the cylinder head so that the black seal on the cylinder head is hidden?
Without the cylinder head, the cylinder fits in snug.

i would not run an aluminium piston in aluminium gearbox. but that’s me.


Ok I have a nylon one I can swap with, can I ask your logic? Potential for damage?

once the coating wears off you will get galling. unless you use a molybendum disulphide lubricant but that is expensive

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Noted thanks i’ll swap

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Is that black bit the oring? If so, it needs to be pushed in further

Yeah it is the oring, it just didn’t feel natural to push it in further. But I have, and now it fits. Thanks

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Yeah they can be a bit stubborn, but if it’s not pushed fully in, it can’t seal completely. Good luck with it