It was partly chasing the Yankee dollar that ruined the Bonneville.
The 650 I always thought an excellent bike if well maintained.
However Triumph Meriden decided, in an effort to appeal the the US and it's then love of big motors, to uprate the engine to 750cc which given that the Bonny in essence was a juiced up 500 speed twin wasn't the best of moves, it's crankshaft and other sundry internals readily agreed with the sentiment. The machine vibrated horribly.
Any power gains were swiftly negated by the emasculated exhaust and intake design needed to meet US emissions laws. On top they decided to bodge fit an electric starter motor, a Lucas unit, which frankly looked bloody ugly and struggled to fulfill it's intended role, in cold weather especially.
The 650 always gave a spirited ride with a nice turn of speed, however the "US special" as it became known was a complete dog lacking in both power and speed.
A motor cycle club I was a member of some years had a member who bought one of these mechanical abortions and asked if he could have a turn on the Honda 400-4 I had at the time. I agreed with the caveat of reciprocation to which he agreed.
From the get go it didn't bode well. A press of the starter tit eventually fired up the motor which as mentioned vibrated horribly. It was reported in a lot of cases this idle vibration would cause the front mudguard stays to break and I saw no cause to doubt it.
The engine, due to the aforementioned emission fittings, sounded like an emasculated bull with none of the Triumph rasp of its earlier incarnation.
Never mind said Fred, let's see what's she's got.
The answer? Absolutely nothing.
A quick twist of the throttle and the thing took off with all the speed and grace of HGV overloaded with cement. Some mitigation could be allowed for the slight drag created by the riders body, caused by the riding position one has to adopt due the fitting of those "ape hanger" style high rise handlebars favoured by American bikers.
When it finally it 50 MPH the vibration became so bad the both the rev counter and speedometer started to rotate in their housings, the front indicator stalks adopted a forward down position plus other cycle parts also vibrating in harmony with the engine.
Other 750 owners reported had similar complaints so this wasn't a Friday afternoon bike taken in isolation.
How it faired over in the US I cannot say but it failed miserably over here with the Meriden works folding soon after.
Some comparison pictures...
he first two show the 750's electric start cobbled on behind the cylinders, I did read somewhere that the gears used were made of nylon!
The second pictures show the classic US 650 and it's ugly 750 brother.