I just got this email from Mac Motorcycles who want to make a cool cafe racer:

Dear Stan,

if truth be told, after Harley’s news about making the Buell ‘Blast’ engine obsolete, we were a bit dejected. The option to produce rolling-chassis for customers in the US to install their own engines was real enough but we really wanted to stay true to our vision of producing complete, British-designed, production motorcycles.
At this point, Mac might well have ended-up “an owners’ club of one” had it not been for ‘Lady Luck’ making a timely appearance. In early May, we bumped into another small, UK motorcycle manufacturer who generously named the source of their new engines. We approached the OEM directly, from whom we’ve had nothing but tip-top support and, as if ‘Lady Luck’ was still rooting for us, their nearest reseller is in our home-town of Worcester, where we’ve found no-end of ‘old skool’ help from a long-standing, family-owned, motorcycle business.
So, we gathered together a small, feral and entirely new gang of chaps, tapped-up our ‘little black book’ of trusted suppliers and set-to to redesign Mac with the new engine. A long-standing work colleague has become my ‘Co-Gaffer’ and now plans Mac’s journey with me.
If you’re anywhere near Birmingham, in Blighty, not Alabama, between 18th and 26th November, come and swing your leg over Mac Mk 2, at ‘Motorcycle Live’, at the NEC (we’re in Hall 3, on stand 3A 10) and tell us what you think. Alternatively, when we get a few minutes, we’ll give our tired old website a ‘make-over’ and you can be an armchair critic.
We look forward to hearing your thoughts…
YS

Gaffers 1 & 2 at Mac MC
+ 44 (0) 7801 633 170 (Ellis Pitt)
+ 44 (0) 7920 259 206 (Ian Oliver)
www.mac-motorcycles.com
spud_black.jpg

the original motor blurb says:
Mac Motorcycles are powered by the Buell® single cylinder, air-cooled, 2-valve, push rod, 492cc, 5-speed 'Blast' engine. They're called "thumpers" and with good reason, with one combustion for every 720° of crankshaft rotation when that cylinder fires, it's really an "event".
I was wondering if it might it be a Loncin or Zongshen engine that they have found?

Any suggestions or thoughts?