Well. I suppose our opinions are based on personal experience (hopefully - not hearsay or Rose tinted rear vision glasses!).
I had a B40 which was a complete pig in every way. Horrible thing, an unmitigated engineering mistake. So unreliable even though it was near new. Terrible starter.
Later I had a Cheney B50MX. This promised everything and delivered very little. It looked pretty cool with it's nickel plated frame and sexy little alloy tank, -and on the rare occasions it went, it was okay, but my Ducati 450R/T just blew it into the weeds.
For years I kept a boxful of worn, broken B40 and B50 kickstart ratchets and quadrants etc. What a heap of rubbish!
The Ducati was brilliant engineering in comparison. Even though it was a 'stretched' 250, it went hard and still lasted reasonably well unless it was slogged at low revs.
We all know that at that stage the BSA factory were cutting corners all over the place, the metallurgy was pathetic. I think the only B50s that hung together were the ones rebuilt by good engineers in sheds, like Cheney and CCM.
The Cheney frame was a gem however, -pity about the B50MX motor it came with. Thank gawd the Japanese came along with well engineered big singles with cams in the right place and balance shafts.
