Project Yamaha AS1
Steve gets his AS1 project straight and ready to take the bottom end
Su s an ia and signi ican progress – my mate Peter had found that despite its rancorous condition, the motor from my AS1 was not only all there, but also rebuildable. This meant I was now effectively committed to the bike's resurrection. Thankfully, these motors run standard main bearings, so no need to be paying stupid money for genuine parts. Some generic Japanese Koyo mains (C3 grade to allow for thermal expansion) hardly dented the wallet so I ‘only' had to throw serious money at a new set of big ends, a pair of conrods, two crank pins and a set of seals! If you're intrigued about how these motors are built, we've already covered this a few years ago with the same job on a 200cc CS3 version of the AS1. Amazingly, the transmission had survived so there was no need to run around autojumbles hunting for cogs, shifters, clutches and the like... phew!
John Lennon once said: “Life is what happens when you're busy making other plans!” In the case of the Yamaha AS1, I really couldn't have agreed with the great man any more. The poor little twin spent years in my old mum's garage under tarpaulin, only seeing the light of day when I wasn't messing about with other old bikes.
Still frequently hosed with easing fluids the odd lump occasionally came free; it was, admittedly, a painfully slow process, but I really wasn't in a rush. When Mum passed away, the house was sold and the Yamaha needed a new home, so for a spring and a summer it lived under the same tarpaulin but outside my house in the back garden. This is often the death knell of old motorcycles, but not in this instance – oh no. The present Mrs Cooper made it quite plain that the rusting remnants of a once proud machine were not going to live indefinitely on the crazy paving and therefore I needed to get it sorted. Scientists have shown conclusively that little kick-starts a motorcycle restoration like an angry spouse! Project YAS1 was swiftly galvanised into action. Before the last of the autumn heat dissipated, an entire weekend was devoted to the unpleasant but necessary task of eviscerating the little 125. First job was to ensure the engine fitted into the chassis without any obvious issues. Okay, so that may sound kind of obvious, but these bikes run open-bottomed frames where the crankcases act as a semi-stressed member. It's not uncommon for owners to run these bikes unknowingly with loose bolts, which can do no end of damage to the mountings.
The rebuilt bottom end was carefully fitted to the rear engine plates and hooked to the front down tube with the corresponding engine plates. Everything looked right and lined up, suggesting the frame was straight – but upon closer examination, the lower right rear mount was out of kilter... quite possibly the victim of an over-enthusiastic engine removal
Scientists have shown conclusively that little kickstarts a motorcycle restoration like an angry spouse! Project YAS1 was swiftly galvanised into action.
post blow-up. It was soon back in place and straight.
All those efforts previously expended upon the oiling of every fixing finally paid dividends when some heat was brought into play. Items such as the axle pinch bolts only required a moderate amount of leverage, and even the axles themselves responded favourably to a tommy bar and some strategically applied percussive persuasion. I have to say here that the use of controlled hammering with something like a dead blow mallet is far too often cursorily dismissed as butchery.
The swing arm spindle was free to turn but not keen on exiting the swing arm, and experience very strongly suggested hammering through the metalastic bushes from the nut end generally ends in tears – and damaged threads. In a fit of utterly atypical lateral thinking, I simply put a ring spanner behind the head of the fitting and tapped it out without issue.
Just occasionally I amaze myself! Slowly, yet inexorably, the pile of liberated parts began to grow.
The Japanese motorcycle industry's love of cross head screws did, on several occasions, prove to be irksome. Some gave up when heated, others required attacking with the impact driver, and a few required a very severe talking to with pliers but most relinquished their decades-old embrace eventually. The only screws really playing fair were those holding the coil bracket around the frame. A Dremel and cutting disc soon had the coils off safely, and the severed screws later drilled out of the bracket.
Amazingly, despite the years of abuse and neglect the tiny twin has experienced, I was heartened to see that the ‘GUIDE, throttle wire' was still in place where it should be – on the horn bracket. Even better, the welded-on pressed steel clip that guides the main wiring harness was still intact. Little details like this make the subsequent rebuild so much easier. If you know everything goes down one side of the frame, there's substantially less likelihood of profanities emanating from the workshop sometime in the future – it's something I've done… a lot of!
I suspect I'm like many classic bike fans who really don't like motorcycle electrics, and Yamaha ones in particular. These small twins seem to specialise cramming virtually every single connection inside the smallest of metal pressings that passes for a headlamp shell. Oh, and of course there's an ignition switch in there as well for good measure. Pictures duly taken, the rest of the loom was slowly liberated without too much drama. But why, please, do home mechanics insist on repairing or adapting bike electrics with wretched screw block
connectors designed for domestic house wiring? I hate bodgery like this!
The loom has already been marked down as BER (an old army term for Beyond Economic Repair), so a Plan B will be required. I could make a new loom from scratch as it's not too complicated, but if an NOS example turns up at sensible money I may very well be tempted.
Final task for this session was removal of the centre stand which proved to be… err… challenging, shall we say. Many Yamahas of the period are similarly prone to centre stand wear and/or distortion. The pivot pin for the stand was never greased during production, and consequently corrosion welds itself in place. The stand then turns the pin in the frame, causing wear. The other well documented problem was owner-related and comes about by riders sitting upon bikes when they are on their centre stands. Over time, leverage and weight pushes the stop or check plate on the back of the stand down, forcing the back wheel onto the ground. This gives the stationary bike an odd stance – not unlike a puppy with worms dragging its posterior across the carpet! Heat and easing fluids, allied to some more strategic yet controlled percussive maintenance, moved the pin halfway. From here it was butchery time with the angle grinder to liberate the stand.
As expected, the pin had worn an oval in the steel cheek pieces of the frame. To add to the joy, the welded-on strengthening shims had broken free. Knowing when enough really is enough, everything was boxed and labelled, tools cleaned and stowed, coffee brewed and biscuits consumed. Occasionally with these old bikes, it pays to walk away while you're still winning.