The 247 Cota is the granddaddy of them all; Montesa's first 'production' competition trials mount, released in 1968, it remained in production with detail changes for a decade, being last listed in the 1979 Sales brochure, though it had been superseded as the preferred mount of the works riders by the 348, in 1976.
It featured a steel, full cradle frame with single front down tube and distinctive mudguard stay 'loop' at the end of the seat tubes; the engine never gained the deep 'crinkle' fining of the bigger and later bikes, or the 'wide' crank case covers that accommodated the heavier fly wheels; though it did get a five speed gearbox fairly early on.
Ted e-mailed me with these pictures of a late 247 Cota he had acquired for restoration; by all the other pics in the back-ground looks like Ted's a bit of a glutton for punishment!
Old girl looks like she's been a bit neglected for a while, but, as I am continually surprised to see, remarkably complete, and a very good candidate for a resto.
Ted asked if I could help him 'date' his bike from the 'photo's he supplied; something I am very often asked to do; though I have to say that it is NOT a very precise art, and I can only ever give a rough guess on age or sometimes even model!
In this case though, the distinctive features are the 'swept' bottom to the side panels of the integral seat/tank unit, plastic mudguards, and the left hand side exit exhaust.
Ted's bike, is shown here, between brochure shots for a 75 model, and a 78 model.
Notice that the earlier bike has chrome guards, flat bottomed side panels, and a right hand exit exhaust. I don't have a brochure shot of a 76 or 77 model, though I do have a pic of a 76T, the 'road' variant with duel seat, which has chrome guards and flat bottom panels like the '75 model, but a left hand exhaust, like the '78.
From the pictures, it looks so close a match to the '78; but, with ten years of production with so little significant change, given some repairs with 'available' parts, it could be an older bike.Notice the narrow crank case covers and shallow cylinder finning, common to all the 247's, even though the engine castings are the same as the 348, 349 & 248.
For 'authenticated' dating of old Cota's, in the UK, for such things as age related registration, classic competition or concourse eligibility, the best place to try is Jim Sandifords, the original importer; they used to hold all records of all the bikes they had imported over the years, and the business is still run by the founding family.
Less accurate, and possible less acceptable to many authorities; there is a frame number directory by model and year, on I think the North-West Montesa web-site.