A few years ago I broke the ring in my '70s vintage Profi .61 two-stroke. My heart sank. I figured the engine would be sidelined for years until I stumbled on a replacement. I assumed when I did find one, it would be a fortune. I would have no choice but to pay the asking price or the engine would never run again.
An e-mail to Frank, $10.00, and a week later Frank sent me a new ring better than the one it came with. This engine had been out of production for 20 years! Really a fantastic ending. I still fly this engine on my LT-40. As far as I'm concerned, Frank is a gift to modelers. I haven't worried about a ring in a model engine for decades.
OK ladies and gentleman. Here's the word from Bowman Mountain:
Frank's rings
* are made from fine graned cast iron and heat treated to 1,850degrees F
* come pre gapped to his bore gage or ungapped
* end gap recommendations on engines under .70 c.i. - .001", .70 c.i. and over - .0015 to .002
Please measure the gap when you get your new ring. I will be very surprised if this is the gap on an 4-stroke ring.
Bill