Saturday 11 February 2012

Moto Guzzi 125

Moto Guzzi? Well, it's really a Benelli. Then again, it was assembled by Triumph Meriden just before they went bust, although there was no input from British suppliers. Confused? Join the club. It can be said with reasonable certainty that it's a single cylinder stroker of 125cc displacement bunged into a reasonably stiff frame with adequate suspension. Well, at least when new, the near wreck I picked up for £75 was an entirely different creature.

It looked like every day of its life since its creation in 1978 had been a very hard one. Amid the blitz of corroded paint, chrome and alloy it was all the more shocking that the engine still ran. Ran as in popping and wailing out of a very dubious bit of metal that looked like part of someone's 100 year old cast iron drain-pipe. I threw a curious glance at the owner's Victorian terrace but could find no immediate evidence of such vandalism.

Neither of us was willing to test the bike on the road, so it was shoved on to my roof rack, where it survived the bumpy ride home. It was just as well that no-one had tried to ride it, I discovered that the front wheel had cracks running through its hub where the disc was attached. One of the few components in good fettle was the front forks, so rather than replace the whole front end I had to find a wheel that fitted. An early AR125 wheel went straight in with a couple of washers for spacers. There was no way the speedo cable could be matched up so I had to bung an AR speedo on to the yokes. No great loss as the stock one had enough loose bits to pass itself off as a baby's rattle. Along with new steering head bearings that sorted the front end.

As expected, the swinging arm bearings were swamped with rust and the spindle proved reluctant to come out. The whole frame had to be wire brushed down to bare metal, rust proofed and finished off, by hand, in gloss black. The back wheel bearing was slightly pitted but not loose, so was swathed in grease. Spokes and rims received identical treatment to the frame.

The sidepanels were flung away in disgust. As were the wiring and electrical components. The petrol tank was neatly shaped and had not quite rusted through, so was given the salvage treatment. The seat was a terrible mess, so a GS125 item was bodged on in its place. The mudguards like the electrics were replaced by ubiquitous Japanese bits from the breakers, source machine unknown.

After a large amount of gunge was removed from the carb and an KH125 exhaust system hammered on, the motor agreed to tick over and rev cleanly, so I resisted the urge to pull it apart; no knowing the state of the alloy in a 15 year old engine, might never bolt it back together again.

The MOT certificate was issued without any hassle, mainly down to my choice of back street tester, although the machine did end up looking very clean after all the work I put in. Tax and insurance were not too expensive, one of the benefits of a mere 125cc and being 42 years old.

What I hadn't realised until the initial ride was that only the first four gears worked. Booting up to fifth put the box in a false neutral with a difference, this one had screaming metal that gave every indication of blowing up the motor. I had soaked the original chain in oil a couple of times, working out the tight spots with two sets of mole-grips, so the final drive didn't aid the precision of gearchanges one tiny bit. Having the change on the wrong side only made things even more complex.

Acceleration seemed quite brisk, with 60mph coming up on the clock in no time at all. However, the revs needed for this in fourth gear were accompanied by vibes that felt just like a dentist's drill was at work on the nerves in my hands and feet. As the Guzzi could pull off in second gear without any clutch slip, I thought the easiest way to improve things was by changing the gearing. Anyone who has ever tried to buy a set of sprockets for this bike will realise how pointless is such an exercise. One wag told me that V50 sprockets would match; it didn't take very long for some supercilious know-all to point out that the bigger Guzzi has a shaft drive.

The exhaust system seemed to suit the engine well, with none of the flat spots that might be expected from such a random match up. It was almost possible to wheelie the bike on take-offs, but a horrible clanging noise from the clutch under such abuse soon dissuaded me. It would run quite cleanly at 20mph in fourth gear, so at first my only object in life was to get the engine in that gear as fast as possible.

However, five miles at low speed produced both loads of smoke and a coked up spark plug. If the engine wasn't given a quick burst of power in second gear, the motor died a death, refusing to start again until the plug was either cleaned or replaced. Plug life worked out at about 750 miles, but I tended to pop a new one in at 500 miles. The first time I took the plug out it was reluctant to come undone, felt close to stripping its thread. A bit of grease on the thread of replacements solved that potential nightmare.

Bearing these constraints in mind, I used the Guzzi in anger for a couple of months, finding it a useful town commuter. Light, narrow and eminently easy to throw about, at town speeds there was nothing much to complain of. The revvy, vibratory nature of the engine meant that open road work was very tiring for more than a few miles in a day, not so much a complaint against the original design as a result of a knackered transmission.

The electrics, I guess, were naff from new. Pathetic six volt rubbish that compounded the insult by almost going out at tickover speeds. Despite my best rewiring efforts there was still a lot of bulb blowing and absolutely no hope of cruising down a deserted country road at night at more than 5mph. It didn't really matter as most of my riding was done in well lit towns.

After 1800 miles the engine showed every sign of being coked up, with unsightly lumps of carbon in the silencer. I'd been using some cheapo oil, mixing it with the petrol being the sole means of lubricating the engine except for the transmission oil. The head, barrel and exhaust came off with suspicious ease, but took a whole weekend to clean up. There was no chance of replacing the gaskets, so I smeared them with a bit of gasket goo.

It was worth all the effort, as the engine screamed with renewed energy, putting all of 65mph on the clock before my fingers threatened to drop off. The frame and suspension were still typically Wop stiff, didn't show any qualms about this new turn of speed. The front disc would sometimes squeak alarmingly, probably down to the mismatched components, but pulled the bike up quite promptly. The back drum was true to its tiny size and irrevocably corroded castings by hardly ever adding any braking forces.

I'd kept the Pirelli tyres the bike came with, quite impressed until the first rain. The front tyre hit a manhole cover, immediately sliding away. By the time my aged muscles were ready to act, it had already hit the tarmac proper again. I got away with a shoulder dislocating twitch from the bars rather than a taste of tarmac. A set of used Conti's were persuaded on to the rims and life became a lot more certain.

Decokes were required every 2500 miles but by the time the third one was due the motor was rattling away like a dustbin full of nails. Pulling off the head revealed a piston that was lolling about on its worn out small-end. The rings were all wrecked as well. There was no hope of finding any used parts in breakers and the couple of Guzzi dealers I phoned up told me where to get off.

As the chassis was rather nice, even if the petrol tank was threatening to collapse, I decided that the done thing was to find some likely Jap engine to bung in. Tape measure in hand I finally decided that an old DT175 motor was just the thing. It was only £25, the breaker even let me pull off the head and barrels to check it over. As might be guessed this proved an amusing way to waste a month making everything line up, the DT motor ending up canted forward more than Yamaha had intended.

Starting proved elusive but three days of kicking and pushing eventually forced the stroker into reluctant life. The DT motor was supposed to have a separate oil tank but I was pretty certain that a 20:1 petrol/oil mix would sort it out. Judging by the permanent oil screen there was some lubrication getting through.

The engine seemed less powerful than the old unit but had a gearbox with a full ration of ratios. 70mph could eventually be squeezed out of the motor, but, again, the vibes ran through the chassis with the same debilitating force. Given the choice, I would've preferred the old Guzzi motor but not having that option I buzzed along on the hybrid for a good six weeks until the hack blew its guts out.

I only survived because my hand hovered over the clutch in readiness, but it was a close thing. The chassis is still in good condition, I'm now working out how to fit a CZ 125 motor some so-called friend donated to the cause. It may turn out to be hacksaw and welding torch job.

Mike