Owned this since 1976.
Old photo, but bike still looks the same. Except the engine is currently in bits, while I try to identify a strange noise........

)
)I thought that fixing the alternator rotor key on mine would have solved the noise issue, but it didn't, unfortunately.(When I found the slack rotor I thought "Yipppeeeee".)
It's a 1968 one.
Does your dad have a Tiger 90 with a 500 top-end as well?
Featherbed and TR1 ?
With Comical hubs![]()

you may find this interesting then. I remember being told it was Yamaha engine but I'm not sure.

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My other half, Tim's beloved Jota - can get a bit noisy following this one!
lovelyhe does ....... amongst others .....you know him ?