LAVERDA 500
Although it’s often overshadowed by Laverda’s tremendous triple, the firm’s 500 twin-cylinder powerplant exemplifies engineering excellence. So says Roger Slater, and he should know! This example needed some TLC to return to tip-top condition…
Although it’s often overshadowed by Laverda’s tremendous triple, the firm’s 500 twin-cylinder powerplant exemplifies engineering excellence. So says Roger Slater, and he should know! This example needed some TLC to return to tip-top condition…
The 500 Laverda twins come in various flavours, based on the same extremely robust engine. In UK the civilised road version was called the Alpino. For reasons no one seems to understand, other that the American tendency to avoid anything NIH (Not Invented Here), the very same model morphs into the Zeta in the USA. The hottedup version was called the Montjuic after its race success held in Barcelona’s Montjuic park. Then came the Formula 500 which is the same thing with full race fairing and completely open exhaust.
Last but certainly not least there is the lovely 350 version. This was an Italian taxdodge exercise whereby a 350 attracted considerably less purchase tax. We sold a handful of 350s in England but they cost the factory as much to build as the 500 with larger pistons, so there was very little interest. All were built like Swiss watches and have a well-earned reputation for being bulletproof.
There’s proof for these claims – the small twin holds the fastest lap on the Isle of Man by a Laverda at 105mph. So reliable were these twins that there was a race class in Italy solely for privateers running their own Formula 500s. It was a 40-bike sea of orange on the start line. The 500 twins were first and second in their class in the Barcelona 24 hour race, not once but on two consecutive years. The two bikes involved were the very same ones for both years; they were not replacements or rebuilds. The winning bike was ridden by my old pal Pete Davies and Agusto Brettoni. I was part of the factory team on both occasions as timekeeper,
so the 500 had personal significance for me. A few days after the race, that actual winning bike was delivered in one of the regular shipments from the Laverda factory to Slater Brothers in the UK, along with 40 new Laverdas. Massimo Laverda personally presented me with the bike.
This little treasure later came us when we moved to the USA. It was put under a blanket, never turning a wheel until several years later when Cliff Carr asked me if I would be interested in entering a new road race event he was organising in Mexico. Meanwhile, Pete Davies had also relocated to this side of the Atlantic. Although he’d long retired from motorcycle racing, Pete was definitely interested. But what could we use for a race bike?
Time to dust off the Barcelona bike.
As the 500 had not been run since its Barcelona victory, I thought it prudent to check it over before the long trek to Mexico. It needed a pair of Dunlop endurance tyres to replace the bone-hard worn-out ones. While
waiting for those to arrive, I removed the cam box to check valve clearance. Unbelievably, no adjustment of the eight valves was called for. No wear to be seen on anything.
Likewise, the O-ring drive chain was still serviceable. In fact the only thing the bike required was the replacement of the sandcast magnesium rear wheel due to some cracks. A standard production alloy wheel went straight on. This again underscores the very sound, almost indestructible nature of the 500 twin’s design.
The race itself was on public roads across the Baja peninsula from coast to coast. We won the 500 class and, had it not been for a mid-distance compulsory fuel stop, we would certainly have taken the open class as well. Despite this unnecessary stop, we were second in the full-blown open racer class at an average speed of… 101mph. That was the last race that Pete and I participated in.
After that demonstration of superior design, brace yourself for the unexpected tale of woe about a troublesome Alpino which follows. It came from a collector who was thinning the herd. When it arrived, I was pleasantly surprised to see that the condition of the bike seemed to be close to the ‘tidy rider’ spec as depicted on the photos sent by vendor. As is normal, the battery was useless. With a new one fitted, the 500 reluctantly fired up. Let’s try it down the lane. Performance was sadly lacking below 6000rpm, after which it would suddenly take off with alacrity. This was indicative of summat radically wrong, and that was only half of it. At anything above idle, the engine vibrated very badly. At the above-mentioned 6000 revs the vibration was very severe indeed. It went onto the bench for some urgent investigation.
I suspected some sort of mess-up with the engine balancer, so off comes the drive side clutch cover for a looksee. Nothing untoward; the balancer was free and running on good bearings. Out with the plugs to check it was timed correctly. Whoops, here we go, the balancer was timed ‘half correctly’ with one piston at TDC. However… that was the wrong piston!
The weight of the balancer must be at its 6 o’clock position with the left piston at TDC. The Laverda 500 twin has a 180-degree crank layout, ie: one piston up, t’other down. This results in perfect primary balance but at the expense of a rocking couple. This couple is the alternating side-to-side motion as first one piston then the other tries to rock the engine sideways. To counteract this, there is a balancer installed which is basically a small steel flywheel with half the wheel missing.
This contraption is of course wildly out of balance, but by timing its out-of-balance nature correctly to the rocking couple of the reciprocating (up and down) parts of the engine, the result is blissful harmony.
Had Mr Bodger left the balancer out, the engine would run acceptably well with some mild vibration. But timed as he had done, the
balance shaft multiplied the side couple to make the engine vibrate like a paint mixer.
With that sorted, the next thing to investigate was the drastic performance lag below 6000 revs. Suspecting Herr Bosch might be on the blink, it seemed prudent to do an ignition scan. With my trusty strobe light plugged in, we could see that the left cylinder firing point was retarded by 8 degrees. The right side was likewise retarded at idle but would not advance at all below 6000 revs. Was this Herr Bosch’s fault… or another legacy from the master bodger?
A butcher’s hook at the pair of Bosch triggers on the left side settled the question. Our ham-fisted bodger had the gap twixt rotor and coils set at double the required gap on one cylinder, and a monster gap on the other. This is an old-style CDI system (aka ‘pointless’). The ignition advance is done electronically. Herr Bosch in his infinite wisdom decided that there would be no ignition advance curve. Instead it was a glorified switch that instantly switched from full retard to full advance at 3000rpm.
This not-so-clever electrickery calls for very precise setting of the pair of small magnetic coils on the left side of the engine under the little round inspection cover. With a 5-thou feeler gauge, a 4mm socket head tool, and considerable patience, it is possible to fix the gap between the coil and rotor at 5 thou: not four, not six, but five. With this done, the strobe lamp indicated that all timing was now as intended, with sparks occurring at the S and D marks (left and right) at idle and shooting up the full advance at 3000 revs. A quick run indicated that all was well with ‘get up and go’ and ‘vibration, lack thereof’. The 500 returned to the bench for general cleaning – but wait, what the heck is this?
While applying wax polish to the petrol tank, my beady little eye spotted a drop of moisture on the petrol tank that would not wipe off. I poked at it with a fingernail,
then explored further with the tip of small screwdriver. This produced lumps of body filler falling out, accompanied by a dribble of petrol. Our ham-fisted bodger had stooped to just about anything to get rid of this bike to some unsuspecting mug. What you may see in the photos hereabouts is a bunch of pop rivets that the bodger applied to the fuel tank’s dent. Why this was done will go down as one of the mysteries of mankind. Draining the tank and shaking it indicated that the ‘tails’ of the pop rivets were still rattling about inside.
After I sandblasted the tank, it went to my highly skilled local tin-basher at Dave’s in Rockford. As is usual, the tank came back from Dave’s looking better than new. My little Breganze jewel was now looking and performing as it should. What a pleasant motorcycle this is: it goes well, handles well, is very light and vibration-free. But wait! The champion bodger was not done with the poor thing yet…
The Alpino was apparently sorted, and my good friends Galen and Mary came to see it. For Mary it was love at first sight, and the little Laverda changed hands on the spot. It wasn’t long, however, before I got a disconcerting message that Mary was having problems with the gearchange. My suggestion to wear bigger boots effected no cure. Next came ‘a big bang’ from the twin’s primary drive and gear changing was very difficult. Time to get the Alpino back on the bench.
As we removed the primary drive cover, a bunch of metallic bits fell with a tinkle into the oil drain tin. The rear of the clutch had been attacked by the gear selector shaft that had drifted out of the crankcases until it
made contact with the small screws holding the cush drive together. All the screws were sheared off and the bosses on the clutch cush drive were mainly gone. What a mess.
How on earth could this selector shaft possibly come out of the cases? It is held in place by a small pin that goes through a drill hole in the lower case to locate with a hole in the shaft. The pin is secured in place by the layshaft main bearing.
It seemed that a fairly straightforward cure would be to Loctite the walkabout spindle into the case behind the clutch. All damaged parts were replaced, and all again was rosy. For a while.
Some months later I received a tentative call from Galen and Mary. The gearchange was not quite right again. Maybe it needed adjustment? Back on the bench: the same-old same-old, but this time the damage was far worse. It was time to get the engine out to find what on earth is going on.
You don’t necessarily need to strip the entire engine to get into the transmission of any Laverdas. The 500 offers two ways of doing it. The factory method is to build from the bottom up. This means placing everything into the lower case half, then the cylinder block and head. The short cut when working on an already fully assembled engine is to tip the whole thing upside down and go from there. The engine comes out of the frame from either direction. Hump the thing onto the bench and invert it, sunny side up. It is a distinct advantage to have a very fit, burly policeman as a neighbour!
Off with both side covers. The right side magneto requires a puller and the crank side thrust retainer is a castellated threaded ring. It is left-hand thread and needs the proper tool to undo it. As you may see from the photos, Mr Bodger Supreme had no such tool, so simply thumped at it with a big hammer and drift.
On the left side, the clutch centre nut is also left-hand thread. With both sides showing only shafts sticking out, it is time to take off the lower case half to reveal the gory details. Once all the nuts are removed, tap lightly round the case with your rubber fivepounder, and do the same on the protruding shafts. Lifted off, we see the exposed crankshaft and all of the transmission gears and their respective shafts.
The ‘go walkabout’ selector spindle is supposed to be held securely in place by a little 8mm x 4mm pin that sits in a small drilling beneath the layshaft bearing and thus entering into a hole in the spindle. There was no pin to be seen, hence the spindle was free to come out far enough to cause GBH to the clutch cush drive assembly.
While rummaging around, you can actually see the excellent internal engineering which earned the 500 engine its ‘Jewel of Breganze’ moniker. Observe that every moving part runs on roller, ball or needle-type caged bearings. Even the right-side clutch operating shaft, which only moves a few degrees each time the handlebar lever is operated, has two needle races to locate it. The gear selector drum that never rotates a full turn has caged ball bearings each end. The crankshaft has two ball bearings, one each end with two massive needle bearings in the centre. Even the starter one-way clutch is mounted on a pair of caged ball bearings. The two overhead camshafts run on no less than six needle races, one on each end of the shafts and two large central ones. I could go on but you get my drift!
Looking into the lower case half, there was enough dirt and debris to successfully grow spuds. The case jointing compound was not the factory stuff. As is often the case with amateurs, it was applied from a bricklayer’s hod and trowel; far too thick.