Greeves Challenger 360 in Movies
On Any Sunday
The motor looks like a two stroke twin and the only one I can think of in a dirt bike of that era is the OSSA Yankee. http://www.yankeetwin.com/ but somehow I don't think this is what it is. The style of paint job looks like Harley-Davidson... It's a Greeves 360 Challenger. Mert Lawwill was a Harley-sponsored rider at the time, so to get the bike on film, he had to put the appropriate decals on his 100% British scrambler! http://motorbike-search-engine.co.uk/classic_bikes/GREEVES_MX4D.jpg
Isn't it high time to acertain this convincing guess?