Man I have to keep relaying this info every few years, LOL
So here's the real deal on these bicycle engines, Don Grubee was in China in 2000 for work and saw what the Chinese were doing with their copy of the Latvian bicycle engine, bought one from a street vendor and brought it back to the states later that year, he put it on an old columbia cruiser and was offered $500 for it on it's first ride. The idea was born! He returned, found a foundry to do the castings and began to source the rest of the part's and made some changes again.
Now Don is old a bit picky and paying good money so he want's what he want's no BS, when casting runs went bad and he rejected them, instead of being destroyed and or recycled they mysteriously got sold off to Chinese companies to do with what they do which is copy everything.
This led to Don having to change foundries and still to this day countless law suits being filled against Zeda CDH and others all due really to a bad contract not having the bad casting dealt with properly, but now the damage is done and the original foundry was still pumping out casting as they found buyers for them which created the knock off market the Chinese are famous for.
So real truth of the matter is they are all knock off Grubee engines and all the real changes over the years have all come from Don not any of the other vendors as they would have you believe, I've talked with Don and he told me all about all of this and back in late 2016 showed me the blue print or mechanical drawings and copy right of the triple 40 setup, when we were discussing the 40mm stroke 17mm mains (6203 bearing) cranks that he'd been using since 05-06 but anyway it's funny how twisted the stories of these companies are and sad that the Chinese screwed Don over so bad.
if you ever get to see a Starfire engine the castings the machining and everything puts all the current ones to shame, when Zeda's castings were really nice at first (not so much now) they came from Don's out sourced foundry when he did the Starfire line.
CDH use's Don's first foundry as did Power King/Runwell and quite a few others back in the early/mid 2000's.