The below advertisement talks about the “new” SR frame. This appeared in the August 1977 issue of Bicycle Motocross Action. That would indicate the bike came out in 1977. The ad also says the bike was tested for three years? Meaning they built the first prototype in 1975.
June 1977
August 1977
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I had one of the first prototypes and it was back in 1975. Steve Rink let me trial it at WSA/Orange and I took first place that night. It was a great bike and I rode it to many wins! That’s me in the photo!
On the gate in lane 1 is Factory Peddlepower rider Kenny Mingus. Nice to see you found the site. Thanks for the info. Got any pictures you want posted just email me at bulletproof2000@live.com