The 4T twin when new caused a lot of excitement for Bond owners. Known as the 60/60 Bond, they claimed 60 to the gallon at 60PMH. Alas that was not quite true and a result many Twin owners converted their cars back to singles. Bonds were supposed to be cheap to buy and run but a Twin was neither. Very few Twins were in regular use until 5 years ago when there was a resurgences in interest.
The main problems are : centre seal on the cranks goes with age or lack of use, pistons, other than standard are near impossible to find these days, there are 2 of everything to go wrong ! and the fuel consumption is really poor.
That said my Twin goes like a rocket and is silky smooth with it. I drive it every where and it has yet to let me down. I took it to Jean's rally last year then drove it to the Isle of Man and back fully loaded with no probs.
I much prefer the 3T as fitted to the Frisky Sport and Scootacar Mk3. Much more power and similar fuel consumption. I was always toying with the idea to fit a 3T into a Bond.
No excuses for not getting yours on the road then Richard.