Super but not stock
Take one shabbyyammy and make it seriously yummy so it turns heads in a show and at the track.
When a motor vehicle, however many wheels it has, is described as 'well travelled', it often means the poor thing has been abused and is just this side of scrap. We know the way this works, the first owner uses the bike and looks after it, the second owner maybe does the same, the third one maybe less so, but still the lad or lass is on the way up, then the fourth, fifth and sixth owners come along - by now the bike is becoming cheaper - and at the level of owner who thinks he'll have a go at this 'crosser lark.
This owner has a hammer, some old pliers and works in the greenhouse belonging to his grandad; the bike dies, a mate in the pub says 'I'll fettle it...' cue more abuse; maybe it does fire up again and it runs spectacularly for a few moments as the fuel lacks that vital component for a two-stroke; and then it stops and it is abandoned in a barn, shed or under a sheet in the garden.
The dirt bike world is no stranger to such scenarios as once a bike's career is over it's often handed on down the line until, well, the end of the line and it doesn't seem to matter if the bike was a works one or a standard model. Of course there are exceptions and this smart, slightly non-standard 1981Yz250is one of them and shows just how things can survive almost intact, despite an interesting life.
Instant marketplace
Thanks to the internet and its auction sites it is pretty much an instant marketplace nowadays, and when coach operator Jim Shand was looking to acquire another race bike for the classic twinshock and evo racing he's a regular in, the internet search he did turned up the ideal bike.
It's never just that easy though, or maybe it is for some people, but not me or Jim. Liking what he saw he pinged off a message to the vendor, the time counted down and he missed it!
About a month later he saw on a well known social networking site that the bike was up for sale again. This time Jim was faster off the mark and bought it from the lad who'd pipped him earlier. What he got was a bike which had been used then pushed into a barn in France, somehow from there it had made its way to Northumberland and then Doncaster before finally reaching Jim's garage in the Midlands. Once Jim had a chance to look the bike over, what he found pleasantly surprised him as the Yamaha had survived the intervening 37 years or so remarkably well and hadn't been abused at all.
That's not to say he didn't intend to fully rebuild the bike, just the starting point was way better than his 125 we featured in a previous issue.
As his intent was to race this Yamaha, Jim made a few changes to the bike along the way from its 1981 spec. Catalogue correct is all well and good but if the correct bit is say £100, but a slightly later bit is £1, and the bike is to be used, then the choice is relatively simple - at least to me. There's also the issue of parts availability too, some bits aren't around so there's little option but to use alternatives.
Biggest concern of a project is the frame, if this is okay then the rest of the project is much easier to
deal with. The good news is it was, and after a small modification to part of the frame to improve a cable run, Jim had the frame blasted and powder coated in black.
Yamaha developed the cantilever concept quite early on in the life of their Mxrange and the 1981 system was pretty well sorted, though would soon be changed for newer ideas.
Its steel cradle swinging arm and suspension mount provided stiffness and actual lightness too, once the bearings were stripped out, this one was coated silver, fitted with new bearings and bushes, slipped in the frame to await the arrival of an Ohlins remote reservoir shock. The original could have been refurbished and used as there is little wrong with it but there is a condition called Yam Hop which isn't a modem dance done by youth Mxers, but something which happens when the rear suspension is not quite spot-on and can have a rider off. Ohlins don't have the problem.
Up at the front end Yamaha had 43mm diameter forks on the YZ as standard, at the time fabulous suspension but like so many other areas of motorcycling, front suspension has moved on. Jim wanted the more modem feel of later forks but obviously to still be in the regs and the first experiment was with 46mm Kayaba units. Great forks but thanks to the travel on them the bottom of the slider sits below the wheel spindle and Jim had an exciting moment at Drumlanrig when the fork caught in a rut ... so fitted 46mm diameter Paioli units which aren't under the wheel spindle. These were correct for the era and NOS from Mastercross. They do give a more modem look to the bike but not too modem.
Interesting
The bike was now at the point of being a rolling chassis and in order to roll it needs wheels. At the rear is a 1985 250 wheel because Jim prefers the feel of its brake. Up at the front is a 1983 set-up because the original brake was a bit 'on off' which can make life interesting. The later twin leading shoe is slightly smaller and has a bit more feel. Yes, I can hear you ... the Paioli forks are a disc set-up and the wheel is a drum brake. There is a neat fitting which bolts in to the caliper lugs on the fork leg and has a stub to locate the brake plate, job sorted. Both wheels wear Dunlop MX3 tyres.
In the engine department new for the 1981 250 was YEIS- Yamaha Energy Induction System - which was claimed to ensure the engine received the same airflow at low revs as it did at high revs and utilising negative pressure in the crankcase to control the fuel flow to the engine. Basically that plastic bottle under the tank at the front makes it easier to ride at low revs.
Jim went through the engine with a fine-toothed comb and as well as a new big-end kit the five-speed two-stroke unit got all new bearings and seals, a new piston with rings. He also matched all the cases and ports so there are no steps or misalignment in the transfer ports, this is a worthwhile exercise in any two-stroke though needs doing properly. Externally the cases, head and barrel were blasted clean and powder coated where necessary so the engine could go back together in double quick time. As well as the YEIS system, there's a V-force reed valve in the induction tract and at the end of it is a 38mm Keihin carburettor feeding the fuel in.
The primary drive is fairly tough on YZS and the clutch got new plates and 465 springs. These are
--The bike was now at the point of being a rolling chassis and in orderto roll it needs wheels."
a bit heavier than the 250 ones but Motokiwi do a clutch lightener for the YZ - and IT for that matter which makes life easier on the occasions when the clutch was used. This isn't always necessary and in the original test Vicallan stated the 'box was tough enough for clutchless changes.
In order to make the bike run, Jim used an Hp!horse Power Ignition - kit which a lot of racers use. The Belgian firm supply all sorts of ignitions and that sort of thing and have a good reputation within the race world.
Given the position of the front pipe it had received a bit of damage and Jim felt a new Pfrsystem from America would be better. These aftermarket pipes are brilliant and end in a repackable tailpipe too.
As things were starting to look good the original idea of using the old plastics went by the wayside and Jim sourced a 1982-83 tank and seat combination which, while not correct for the year, looked fine to me and to a lot of others who walked past the bike as I was taking pies. The later seat allows a rider to move up the bike a bit better as it covers the rear of the tank. He matched these to later sidepanels too as well as new guards and the whole effect is stunning.
Up on top of the fork yokes - sorry, can't call them triple clamps, I'm a Luddite, I admit it - are Renthal 'bars and in Jim Shand's preferred 'Carmichael' bend on these are Domino controls from off-road only and Venhill cables. "I use Renthal medium grips," says Jim, "and I've got footrests from a 420 KTM on the 250. The kick-start is a 1983-85 type which fits straight on and the gear lever is the original 1981 item."
He went on to tell me all the fasteners have been replated or replaced, this is something which seems to have sunk into the consciousness of rebuilders, no matter how good a bike is done, if the fasteners look crap it will detract from the finish.
With the bike almost ready, a Turin-air filter went in to the airbox, Jim topped up with his favourite brew of Avgas and Putoline Mx7oil - just to be clear this brew went in the bike not Jim! - and went out for his first race .. .
Oh dear ... talk about disappointing ... back in the paddock out came the air filter and some massive holes were drilled in the 'box, back in went the air filter and out on the track for the next race things were way better.
As we spoke to Jim at the International Dirt Bike Show 2019 he was looking forward to a season's racing in 2020... well, we know what happened to the season. Still 2021 will soon be here.