Jawa 500 OHC Czech luxury
Ask almost anyone what comes to mind when Jawa is mentioned and the answer is invariably ‘two-stroke’, and perhaps, ‘solid and reliable’. But just when everyone least expected it, Jawa produced a classic four-stroke design.
Czechoslovakia had ridden out some rough times up to 1948. After the shotgun rocky marriage between the Czechs and the Slovaks in 1918 and the subsequent cultural and religious battles, some progress was made during the thirties, with rapid industrialisation resulting in a period of relative stability and prosperity. Then along came Adolf Hitler. From September 1938 until the Soviet liberation exactly six years later, Czechoslovakia was anything but stable and prosperous.
As the ‘thirties dawned, the country added a new name to its list of motorcycle manufacturers. Jawa was formed by Frantisek Janecek, who took over the remains of the German Winklhofer & Jaenicke company, who marketed their products under the Wanderer brand, the new company being a combination of the first two letters of his name and Wanderer. A series of well-designed and reliable models followed, powered by a variety of two stroke and four stroke engines.
However with the Nazi occupation, the Jawa factory was turned over to weapons production. Janecek’s health was failing too, and he died from lung cancer in 1941. His son Karel took control of the company and continued development work on new motorcycle models which had to take place in extreme secrecy lest it be discovered by the occupying German forces. When motorcycle production resumed post-war Jawa introduced a brand new model, the Perak (“Spring”) – a 250 single two stroke with a square section steel tube frame that gained an immediate reputation for reliability if not outright performance.
But there was turmoil ahead, with the Kremlinbacked Communists seizing control in 1948. Karel Janecek decided enough was enough and fled the country, while the new regime wasted no time in nationalising everything in sight, including Jawa, which was merged with Ceska Zbroiouka to form Jawa-CZ. The new entity brought some benefits to both sides, notably the relatively new CZ four stroke singles. The commercial side of the operation was handled by the state-owned Motokov agency. The much-expanded range also included the products of the Oger company which was swallowed up by JawaCZ in 1947. Soon a range of twin-cylinder DOHC racers appeared, designed by new recruit Vaclav Sklenar.
A step up
Just why the company decided to produce a luxury road-going vertical twin is unclear, and why the Soviet overlords allowed it to happen even more obscure, but in 1951 out rolled a rather tidy 488cc roadster, powered by a single overhead camshaft engine. The new model was shown at the FAI Exhibition in Italy in February 1951, and a week later in Amsterdam.
Designated the Model 15/00, the new model bristled with original thinking, such as the skew-gear operation of the camshaft, the use of magnesium alloy for engine components, including the crankcase itself and both side covers, as well as the rocker box, and the fact that the unit construction four-speed transmission featured a semi-automatic method of gear change. By applying pressure to the foot-operated gear lever, the clutch was disengaged, permitting the rider to dispense with the hand clutch lever. In 1958 Triumph came out with a very similar system which was called Slickshift. The feature was especially handy in traffic, whereby the rider simply depressed the lever when at a standstill and released the pressure to accelerate away. The gear lever and kickstart lever sat on a dual shaft, meaning a left-side kick to get the machine going.
The chassis closely mirrored that of the existing CZ 350, however in order to fit the taller engine, the bottom frame rails were replaced with a ‚
section of flat steel bar, which also had to mount the centre stand. Apparently, this was a highly unsatisfactory arrangement, especially for the centre stand which often parted company with the frame. At the front sat the familiar telescopic front forks, but with stiffer springs, while a plunger system controlled the rear end. Rather than being simply un-damped spring units, as was the case on many British bikes, the plunger housings contained telescopic hydraulic dampers, and despite the almost wholesale move to swinging arm rear suspension elsewhere, the Jawa 500 retained plunger springing throughout its production span. Brakes were quite narrow 8-inch steel hubs with an alloy front brake plate and steel rear.
The frame was constructed from square-section steel tubing, with substantial steel pressings for the mudguards and the very Triumph-like headlight nacelle. The fuel tank, with its chrome-plated side panels and red-painted centre section, mirrored the other models in the Jawa range. In the centre of the tank sat a combination ignition and lighting switch which had no fewer than seven different positions to select the desired function. There were many practical touches in the design, such as the air filter which was encased in a recess in the oil tank, and the throttle cable routed inside the handlebar. The purchaser could stipulate any colour as long as it was red.
A well-kept secret
With Czechoslovakia’s isolation from the western world, precious little was heard about the new 500 twin, and the model (nor the merged Jawa/CZ range of lightweights) rarely displayed at any of the major annual shows such as Geneva, Paris and Milan. Even the big Earls Court Show in London saw no representation, despite Motokov opening an office in London in late 1953, primarily to market the 125cc-250cc two strokes.
Consequently the western markets remained oblivious to the Model 15/00, and it was 1954 before a revised model was released and found a few homes outside the Czech border. A sign of the slight thawing in the cold war was Jawa/CZ’s presence on a lavish stand at the 1955 Paris Salon and at the 1956 Geneva Show. The new model carried the 15/02 designation and whilst the engine remained largely unaltered internally, with a light increase in power, a major change was the dropping of the skew-gear method of operating the overhead camshaft in favour of a more conventional bevel drive arrangement. The other visible change was in the wheels, with massive ten-inch full width hubs and much improved brakes. A new, heavier front oil/pneumatic telescopic fork was fitted for 1957 and a dual seat became standard fitment to replace the traditional sprung saddle. But Jawa’s fortunes were still very heavily directed by the Eastern Bloc powers, who saw little benefit in marketing a luxury sports twin, and preferred to satisfy home-market demand for the 350cc Model 354 which was capable of uncomplainingly lugging a sidecar crammed with humanity, and required minimal maintenance. In 15/02 form, the 500 twin soldiered on until the end of 1957, then quietly disappeared. These were still rare bikes in western Europe, and almost unknown outside Europe, until the communist system began to dissolve, first with the reunification of the two Germanys and soon after with the collapse of the Soviet Union. Surprisingly, Australia was one of the few markets outside Europe to receive the 500s, but only in very small numbers. One Jawa 500, complete with sidecar, ridden by Victorian Russ Corrigan, even started in the infamous Redex Trial of 1954 and completed the 2,500 miles (4,025km) ordeal, held in the middle of the most severe Australian winter for decades, with a loss of 1228 points, classified last of the 71 classified finishers from a field of 138.
The racers
With sales of road bikes booming post-war, the new Jawa-CZ concern was able to finance the development of a new stable of racing motorcycles in 248cc, 348cc and 498cc. These were also parallel twins, but with double overhead camshafts. While Jawa was keen to float the notion that the racers had been developed from the 15/00 roadster, the 500, officially named the Z 15, was substantially different,
with a bore and stroke of 65.75 x 73.6mm. Each of the camshafts was supported by three roller bearings, and driven by a vertical shaft and two sets of bevel gears. Power was claimed to be 45hp at 7,000 rpm with a top speed of 128mph (206km/h). Like the 15/00, the frame was made from square-section tubing, with telescopic front forks and swinging arm rear suspension. It sat on fat 16-inch tyres, with a massive 250mm front brake. Elektron was used for the crankcase castings.
Initially, the Jawas raced mainly at home, with occasional forays into non-championship meetings in Europe; the 500 making its GP debut in 1956 at Assen. However the main thrust of development was on a new 250cc design which had more than a passing resemblance to the NSU Rennmax. This appeared in 1956 and was increasingly developed over the next decade, along with a similar 350. By the early 1960s, the 350s were very competitive, finishing second and third in the 1961 World Championship. In fact, the old, heavy 500s were eventually parked and slightly over-bored 350s used in the Senior races on the odd occasion when the factory team, with its limited resources, chose to enter.
From the owner: Rob Fromm
The Jawa was bought in 1989 from my uncle who lived in Adelaide, who had purchased it in 1976. My uncle had completely dismantled it in preparation for its restoration, but unfortunately he had not been able to continue. So I purchased boxes of parts. When it arrived home, I rebuilt the wheels and greased them. The Magneto was rebuilt professionally. My motivation to continue this restoration was high, but the project did not re-commence until 2004.
The first and probably the hardest step was finding any information about this particular model. The internet today is a big help; I connected via email with a Czech Republic Jawa rider, but the language difference was limiting. He had sent me a parts book, all in Czech, so I was trying to work from pictures, until I was lucky enough to find a parts book in Melbourne (in English). This book lists every nut and bolt, including length, diameter and pitch of thread. This was invaluable because a large number of bolts had gone missing, and I had to make them, or source from somewhere.
I also acknowledge two Jawa enthusiasts in Adelaide who had raced these bikes years ago.
They helped by telling me how the crankshaft came apart. The crankshaft is tapered and splined, with a master spline to keep alignment and then a long bolt through the assembly which holds it all together. These enthusiasts also helped with information about valve and ignition timing, and sourcing front fork seals from Czech Republic. Valve timing is achieved by a vernier arrangement hence many variables. Crankcases are magnesium, as are the engine side covers and the rocker cover. ‚
My bike has a Lucas Magdyno fitted, which is correct as apparently when they left Czechoslovakia to go to England, they were changed from coil ignition to Magneto. Early motors had spark plugs stopping 3-4 mm short of the combustion chamber and only connected to the combustion chamber by a 6-8 mm hole. Possibly this was to protect the very fragile spark plugs available in the period or maybe the low octane pool petrol. The crankshaft has easily obtainable roller bearing on the drive side and a ball on the timing side. Big-end bearings proved impossible to get in Australia, so a machinist friend took measurements and those were sent to Czech Republic and in due course the loose roller bearings arrived and with a very little grinding on the outside of the outer cone by an engine reconditioner, they fitted the con-rod eye perfectly.
The cylinder head was soaked in diesel for six months as it was quite rusty from being off the engine for many years. Then I was able to get the camshaft out; the camshaft is housed in two aluminium pillars with one roller bearing and two ball bearings supporting it. A large externally threaded aluminium nut on one end that screwed into the pillar had to be made as the original had broken. On these early motors the cam is driven by shaft from a bevel gear at the bottom to a worm drive at the top, the backlash necessary for this type of drive makes the engine quite noisy at idle. Later engines had bevel drive at the top as well. The head had new guides fitted and original valves lapped in very well. All the double valve springs were ok. The 4-speed gearbox was good and only bushes and bearings were replaced, new clutch plates were fitted and interestingly the clutch can be operated by the handlebar lever as well as by the gear lever via a cam arrangement, similar to some Triumphs of the era. The engine has two gauze oil filters and I have been able to find an off-the-shelf paper type filter to replace one of the gauze ones. The engine oiling system is by dry sump, with a gear pump.
The large oil tank with a filler cap on both sides (one with the filter inside) of the bike frame sits directly behind the carburettor and a gauze air filter fits neatly into a cut out in the oil tank.
The restoration of the frame and mudguards was straight forward (there were no rust problems), so I only had to sand blast and paint and repair a few dents and cracks. The seat is cantilevered by springs hidden under the fuel tank, and has a friction damper fitted. New linings were fitted to the brakes and prove to be quite good for the era. The back wheel is a quick release type and fits into a spline in the brake hub. The throttle twist grip operates on a large thread moving a slide along a slot cut into the handlebar, therefore keeping the cable straight, rather than bending it around the twist grip.
The bike was finally registered in late 2008.
Since registered, I have travelled over 2,000 miles. It is nice to ride being so small and light. It likes to cruise at about 50 mph (speedo still in miles) and handles very well. Unfortunately, it has been out of action due to oiling of right hand spark plug, which has taken much time to diagnose and repair (hopefully!). I had to get the Magneto rebuilt – again – possibly because it sat waiting for action for 20 years. The oiling problem persisted until I found a crack in the right hand inlet valve guide. I have replaced the head, and will repair the old one for future backup. All motor bike restorers can probably relate to how long and how continuous this restoration process is.
It is back on the road now, and I am very satisfied that I was able to complete most of the restoration myself. When out and about, people often are surprised, commenting that they didn’t realise that Jawa had made 4-stroke road bikes – being more renowned for their 2-stroke machines.
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