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Discussion Starter · #1 · (Edited)
I just pulled down my mystery motor last night and found a set of early 74mm pistons installed. Problem is I can't find a makers mark anywhere and I need new rings. Wondering if anyone had some ideas of who made big bore pistons like this back in the day and may know where to find rings.
 

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You are most likely going to need to get rings from a specialist. They will need the dimensions of the ring lands and will need to fit them. I'm sure there are a lot of bikes in the 1000-1100 size capacity that have a 74mm bore. If you can find a wider set a machine shop could enlarge the piston groves to match.
 

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Wiseco, Powroll or Rocky piston kits possibly

Sent from my SM-J320V using Tapatalk
Not Wiseco, that's for sure. These photo are a Wiseco - easy to see the difference in quality here.
 

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Yeah, they look like cast Powroll or Rocky to me - and probably around 10:1 compression ratio or so, not real high. Might be tough to find rings for them without custom cost
 

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It was my understanding from internet search that they had closed long ago - but I found this today. Looks like the service might have gone downhill though based on some of the recent reviews. They used to be great back in the day, they stroked an SL90 crank 1/4" for me when I was in high school and I bought many of their big bore piston sets, including for my 450 drag bike in the early '70s

https://www.facebook.com/pg/Powroll-Motor-Performance-143457245732920/reviews/?referrer=page_recommendations_see_all&ref=page_internal
 
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