Modded Montesa…
Everyone likes to know what goes into a winner, so we asked the rider of one…
…makes a magnificent, masterful motorcycle… The winner from the 2019 Leven Valley Two-day Trial.
Montesa, despite being the second of the Spanish manufacturers to enter the trials fray in the Sixties, soon had a worthy product, thanks to the help of riders such as Charlie Harris who suggested the initial mods needed to their trail type bike and indeed brought the Barcelona company its first successes.
He was followed by Don Smith and Gordon Farley, who did so much to popularise the model and Farley was to take the British trials championship on his works developed machine. As ever, with such success to promote the machine, sales were on the up – it helped of course that the product was a good one and in many cases easier to ride than the opposition.
Once Jim Sandiford got to grips with the importership, Montesa in the UK were on the up and by the time this particular bike was produced in 1978/1979 (it’s a ‘T’ reg), Sandiford and Montesa were major players. They had an enthusiastic team in their Lancashire HQ, dedicated to the marque and keen to suggest modifications to the factory and many club riders bought a Cota. These days, Montesa still has a dedicated following and with the popularity of twinshock trials the Cota is being seen more and more in action.
The tale of woe which befell this particular Montesa is explained further on in the feature, suffice to say here the initial rebuild got the bike up and running but since then it’s had more work done… a lot more work.
But, to step back a bit to the early days, there are a lot of parts on a motorcycle which don’t react well to extreme heat such as is experienced in a fire. Naturally enough the tyres, tubes, mudguards, cables, oil seals, petrol tank cover and seat were all destroyed, being of rubber, plastic or glass fibre, but the frame, engine, wheel rims, airbox, exhaust system and a few other metal bits and pieces were salvageable.
Once up and running, its owner Paul Norman used the bike for a few trials, then laid it up when another came along. A chance conversation with Butch Robson saw the Montesa heading east from Carlisle to Castleside and a slightly more in-depth rebuild for the poor abused thing.
The starting point for this machine was a Cota 247 C which, according to the manual which came with my own version from that time, is of 237.5cc.
The year before though the 247 would be 247cc and had the French licensing authorities reduced their capacity cut off from 250cc to 240cc, so would things have remained. This change affected every 250cc trials or enduro motorcycle as they would in those days generally be road registered and the 250cc class was also a learner legal capacity.
No matter, the whole scene was 10cc less, one could of course order, at extra cost, a full-sized 247, but most people waited until it was rebore time. This local regulation thing also affected other areas of a motorcycle and thanks to the café racer craze of a few years earlier, when badly made glass fibre, five or more gallon race tanks for such machines as Tritons, churned out in here-today-gone-tomorrow back street shops for 27/6 plain or 30/- with stickers, gained a reputation for exploding and led to the material being banned.
There was no problem with quality made tanks but a blanket ban was in force. What this meant for the Spanish trials industry was for the UK – an important market – an all metal tank was needed. Montesa created a slave tank from alloy, mounted it under a cover which was effectively the top half of the, still legal in other markets, glass fibre tank. This kept the machine looking the same for all markets and met the law of the UK.
With so much fire damage destroying original components there have been a few replacements which were used to get the bike going – the petrol tank for instance, resplendent in Montesa red is actually a steel TY Mono one which was available. Where the original cover would have a seat built in to it, what was cobbled together here was a temporary aluminium sidepanel and seat. We’re assured by both owner and rider a different arrangement is planned and indeed in production, but there have been other considerations to deal with which took priority, things like the engine.
Though fully stripped and rebuilt, (the thinking being the low-life who nicked it ran it on straight petrol and everything was worn thanks to too little lubrication, see p15), there were still some issues with the engine. Bearings and seals are fairly common and easily matched but pistons are not so common and the pattern piston which went in caused a lot of headaches at first. First problem was to deal with the piston crown hitting the underside of the head and at the other end of the barrel four base gaskets were used to even get the engine to run badly.
With piston ported engines barrel position is critical, as moving it up or down by different gasket thicknesses will alter the port timing. In the end, once this particular penny had dropped and the port timing measured, it was found to be 25% out… a lot!
Replacing all of the base gaskets with the single one it should have, then machining the piston, brought things back into the realms of normalcy and Ossy Byers machined the cylinder head to achieve the correct compression ratio. Once this was done the engine began to perform more like a trials bike. Butch added a 26mm Dellorto carburettor, which is smaller than the standard 27mm instrument, but gives a smoother ride – who are we to argue with a winner? “It will run quite happily with a 28mm carb,” says the lad, “but it’s a lot sharper and I prefer the softer power delivery of the 26mm one.”
The rest of the engine is the standard five-speed
Cota unit with its geared primary drive.
Clearly not standard is the frame, and a Montesa of this era should have steel tubes running under the engine and a steel mesh to protect the underside. Butch didn’t know who had done the modification saying only a cryptic “…like this when it arrived but it’s been well done. It was Andy Bingley who did the frame mods in I think 2011, I had a 247 in the Seventies and it had been altered in the same way, Sandifords did several this way, saves a bit of ground clearance. Oh and while he was at it he moved the footrest mounts back a bit.”
Still on the chassis, Butch told me the fork yokes were made by Gerry Minshall and he fitted the forks from his own Fantic 200.
“They’re set up for me and I’ve used them on all sorts of bikes, there’s nothing fancy inside them, just well prepared and working properly with 7.5w oil in them.” The drum brake on the front is a standard Fantic one and like most people, Butch uses a Michelin front tyre. Things are a little different at the rear though, the hub is pretty much as Montesa made it but the brake plate has had some serious welding.
Originally, the plate would have been located by a long torque arm requiring several tools to remove the wheel in an emergency, which is okay if the emergency is in a club trial and you’re in sight of the support vehicle. However, in an event like the SSDT having to carry a lot of tools is a pain – two ways to tackle this are to make sure one spanner will undo a lot of bolts, or make the wheel need only one spanner to undo it. This latter method is the one done here and the plate is built up so a stub welded on the frame can locate into a slot on the plate. As for the rim, well it is a tubeless type, since Michelin stopped making tube type X11s tyre choice is limited if the standard set-up is in place. However, the twinshock scene has no problem with going tubeless so that’s what’s on here, the tyre is a Dunlop because that’s what Butch prefers.
Once the bike is up to rolling stage the ancillary bits can be hung on, there’s had to be a bit of creativity
here too, take the airbox for instance. It was a pressed tin affair on the original which was protected by the rear mudguard which was formed out to create a shield.
A smaller mudguard needed a different arrangement but when you are a time-served welder with the talent and ability to create things from any metal you fancy, then creating an alloy airbox is easy.
While he was at it Butch made the airbox bigger so the engine can breathe a little better. The filter?
A Beta 80 one. Now, getting the mixture in the engine is only one half of the process and getting it out is just as important. The internet is a wonderful place and one of its benefits is when some stainless steel bends of tube are needed… they’re there for the asking. Again welding these things are a simple task to a welder and the exhaust pipe may look similar to the original but it is tucked in a bit more and matched to an alloy middle box and ends in a WES tail pipe.
What else do I need to know Butch? “Well, Ossy Byers at Audit has been more than a bit helpful with engine mods; I’ve Renthal bars on the front; Domino controls; all new cables; more modern footrests…” he stopped as we both looked over the bike.
That side stand looks a bit fancy, is it an old Renthal? “Hah! No it’s not, picked a few sets of alloy bars up at Telford last year, everyone laughed and said they’d bend first time the bike went over…” Butch smiled, they didn’t realise I’d bought alloy tube with a handy bend in rather than handlebars…”