I took the cylinder off my 1974 DT174 earlier. Turns out it has an oversized piston. I measure it to be 67.8mm which seems a bit odd to me.  I could do with  new rings and maybe a piston if I can find one.  Any one recognise the marking on this piston?  Piston crown only has an arrow on it...

Many thanks

Edit: I pasted an image and attached one but not sure either of those actions worked. Let me know please!

Pictures not work. You need to share a link, almost looks like your copying the whole web address. Anyway, let's say the stock bore is 66mm. The piston itself will be slightly smaller than that. That particular size makes me think 68mm, aka 2.0mm over or .08". Usually oversized pistons have a stamp on the top that will say 0.5, 1.0, 1.5, etc. Wiseco pistons Usually use inch measurement stamping.

Figured I'd add, if it is that far oversized, and 66mm is stock size, you might have difficulties finding another piston.  And I'm unsure how far you can safely bore those 175's, but I know alot of 2 stroke cylinders are maxed at 8 sizes over.

Link to picture worked ok.

Thanks all. It does look to be overbored as there is no bevel on the lead-in at the base of the cylinder. I might just try some +2mm rings, adjust the end gap and see what happens. Not much to lose really and it should be close enough. It ran fine, and I only took it apart as part of winter maintenance.

Odd thought, but normally the manufacturer will only make sizes up to 1.0mm over.  I wonder if that bevel remains, until you go past that oem overbore size?  Random thought, no need to comment.  Feel free to ignore lol.

Yes, I think you are correct. The bevel would remain with the standard over sizes. I think in this case, a non OEM piston and ring set were used to take it out to close to a 68mm bore, losing the bevel in the process.

Will report back once I've put a +2mm ring set in. These bikes are very tough so I'm confident it will work one way or another.