Could this be the correct rear fender?
Sudman, that could well be very close to the real deal.
Those double plate sections for the swingarm pivot I reckon are typical of CMS.
Are their any other frames that you know to be a Champion that have similar gussets?
Geoff, as you would know, the double plate sections are typical of CZ frames of the era. Its just one small step from there to box them in. I don't know of any chapion frames that used it tho.
Champion frames are pretty distinctive and unless Shwerma produced a different, one off design for the Bultaco, I'm willing to bet my goolies on the Spanish GP bike being a CMS. Even though Champion are more noted for their flat track frames, their motocross design is very similar bar slight differences in the swingarm, footpeg mounts and steering head angle. Greg Bastek was recently trying to flog a Champion MX360 motocrosser on the Swapmeet and it was very different to the CMS in overall concept and layout(while acknowledging the twin/single downtube difference).
Yes Mark, agreed - champion frames are generally quite distinctive. I've long believed the yamaha-engined frames are very Maico-like. But the 71 Schwerma Bul frames are distinctively Bul-like. It takes a fairly keen eye to spot the diffs from Pursang/Bandito frames of the era.
I personally can't put much weight on a claim that CMS built Pomeroy's 73 frame. I've seen too much folly claimed over the years in US mags, esp where it concerns US products/expertise etc. I went thro a heap of 73-74 mags yesterday & I found several similar snippets/ads on CMS Products, but only that 1 mentioned any claim that they built Pomeroy's frame. And even the wording of that is not clear who actually made the claim.
My take is that if it were true, CMS would have been splashing it everywhere, in every frame ad. Also, since the magazine pooh-paah-ed the claim, you'd think if it were true CMS would have followed it up & got an apology. What I'm chasing is conclusive evidence, or at least verified from more than 1 reputable source.
With some more evidence I found last night, I'm now inclining to think we will never know who made the 73GP bike frame. I'm not even yet fully convinced that it was US made, or that CMS existed in early 73, tho I do think it was most likely a cro-mo frame.
Hopefully I'll be able to post a few pics later today to show what I'm talking about.
(Just as an aside, I found CMS apparently made 2 CZ frames, one for pre-73 Zeds, & one for post 74 Zeds.)