piston / rings

[Steve]

AJS 350 model 16 MS 1953

Hi all
a query I'm still slowly cleaning and polishing the engine parts slow work rubbing down as much casting marks as I can so I can polish as much of the aluminium as I can, but I digress.
the reason I'm here is piston and rings on the top off the piston I can just make out + 30 the top of the piston is I would say a shallow pyramid with a flat top. I should have taken a picture but dose it sound like the correct shape.
it's a good job I decided to strip the engine as the top ring was in 3 parts also it was, I would say T shaped with the outer edge being wider than the main part hence T shaped. is this normal or has it worn like that.
I've put the rings in the bore to measure the gap. the middle ring had a gap of 1.3 mm - 0.051 imperial and the oil ring 1.94 mm - 0.30 imperial.

should I replace the piston and rings or would just the rings be ok
the bore and piston are not scored.

any help / advise is always appreciated. thanks in advance Steve

[1608]

The bore sounds too worn to me.I would re-bore to +40 with new piston and rings. The ring being T shaped suggests to me that somebody has replaced the rings in the past when the bore was well over size causing the ring extended too far out from its groove or land. The groove in the piston also being worn allowing the ring to judder up and down in the groove. Or, the ring was the wrong thickness. imho!

[Steve]

The bore sounds too worn to me.I would re-bore to +40 with new piston and rings. The ring being T shaped suggests to me that somebody has replaced the rings in the past when the bore was well over size causing the ring extended too far out from its groove or land. The groove in the piston also being worn allowing the ring to judder up and down in the groove. Or, the ring was the wrong thickness. imho!

yeah, kinda thought that may be the case, I did think when starting that it didn't seem to have great compression.
does the piston shape sound right, the top of the piston is I would say a shallow pyramid with a flat top I've only had flat or slightly domed in my other bikes but then I've not had one this old before.

cheers steve