Mark, Doug Schwerma was operating as "Cycle Services" prior to "Champion". The article I have is from June 71 Motorcycle World. His cro-mo Bul frames are visually identical to std pursang frames of the era (as was Pomeroy's 73GP bike) but were said to have steeper rake (typical of Schwerma frames).
The 1st I ever heard of CMS products was a Dirt Bike ad in Nov 74 for CZ frames - long after that 73 GP. Pomeroy's later factory Bul (which by then featured forward mounted shocks) featured in Dec 74 DB had a frame visually diff to the CMS pursang frame - tho one has to say, there are similarities.
Geoff, the diff between the CMS frame & the 73GP bike, apart from the FMS rear end, is in the construction of the rear subframe. The seat rails on the CMS sub-frame are flat & continue on to the rear loop (where there is an upward kink behind the top shock mounts), w the rear upright tubes butting up against them.
Pursang frames of the era (c72-75) are distinctive in that the seat rails are short & butt up to the rear uprights which continue up above them then bend horizontal to form the top shock mounts & have a smaller tube rear loop inserted into them, which then kinks up again for the mudguard. The rear of the pursang seat is cut-away for the raised shock mounts (if that all makes sense - it should if you look at a pursang frame).
Pomeroys 73GP frame was just like the std pursang frames. Other pics of Poweroy's frames from the era (now at Hugh's Bultaco) also show them visually the same as mk5-8 prod'n pursang frames.
However, does anyone know the beginnings of CMS Products? (Edit, I see Geoff' posted above while I was typing)
I'm beginning to wonder if there's a link between CMS & Schwerma/Cycle Services/Champion. I have a pic of what is said to be a late 74 Champion-framed Pursang & it appears all-but identical to the CMS frame in the ad Geoff posted above. Not only that, but the 76 125 prod'n pursang frame is also all-but identical to both, except for diff gussets on the swingarm.
Was Charlie Cole formerly an employee of Schwerma, or vice versa? Or were they mates? Or did one produce the other's frames at some stage?