Foibles and upgrades

MZS are unusual and arguably quirky by anyone’s standards. It has to be remembered that their prime reason for existence was as utilitarian transport so many fripperies bestowed on even older Japanese bikes were often missing or low-rent versions thereof. In 250 form, all but the early Trophies and Trophy Sport run an engine that hangs from its cylinder head via a rubber coupling which isolates most of the vibrations along with the gearbox mounts. The engines jump around at tickover but that’s the worst they get. One of the main differences between MZS and pretty much everything else is the engine speed clutch that sits on the left end of the crank. It’s adjusted from a plate on the outer casing that also carries the tacho drive on many models. Water can enter the gearbox via the clutch cable and, long-term, cause damage to both transmission and the main bearings that also run in the gear oil. Various cures are used to overcome the poor cable sealing and a favourite is to use an electrical pyro cable sealing sleeve. Until disc front brakes were fitted MZ braking was marginal to say the least. As an example, the Supa 5 ran the same sized drums front and rear yet the operating arm at the front is actually substantially shorter because it lives behind a decorative alloy cover plate. This passed for styling in the Eastern bloc! A long time cure was the fitment of a front wheel complete with brake from any Honda CB250/350. The wheel has to be turned around to accommodate the torque arm and a pair of spacers need to be turned up for the axles; the improvement is dramatic. Suzuki GT185S have been robbed to sort out the braking of the ES250/2 and one of our test bikes runs twin-leading shoe units from a Yamaha YDS7 with a brake plate locating block welded to the lower fork leg. Until the advent of the ETZ the 250s were infamous for carburation. Simply put, you could have a functioning tickover and eight-stroke surging on the over run or run on a dead throttle with no tickover and

know the bike wouldn’t jerk and surge when the throttle was closed at speed. The cause was the jetting, design and air passages in the BVF carb. The acknowledged cures were to fit Mikuni units from Suzuki TS250S or T500s. Our test bikes are both equipped with 350cc Yamaha YR5 units, with just a larger 135 main jet fitted. Pre ETZ, the switchgear looks truly naff and rudimentary making even early Italian units look viable; however, they work surprisingly well but are unquestionably counterintuitive. Many Supa 5s and Trophies had Jap units installed; our test bikes run Yamaha FS1-E DX units. Good earths make the most of the 6v electrics but many opt for rewiring with new wire and modern connections which is a good idea. A 12v MZ-B aftermarket ignition gives fantastic lighting and you never need reset the ignition timing. Old wives’ tales still tell of main bearings that’ll fail in short order. The truth is that Mother Russia insisted that the Zschopau factory took Soviet units rather than East German ones. The Commie balls were total rubbish and many were replaced under warranty or good will by dealers sympathetic to the cause. Some bikes had nasty drive chains fitted with pressed rollers running open seams. It was not unknown for the chain to snap, taking out the rear sprocket, chain gaiters and occasionally the front sprocket casting. Mz’ers are a loyal bunch and many do countless miles on bikes they’ve owned for years. A sorted 250 is a seriously robust piece of kit and it was ever only the strictures and dictats of a Soviet state that made the bikes anything less than reliable. Everyone has their favourites but one of the best is a hybrid running the barrel of the Supa 5 grafted onto the ETZ. This gives a relaxed torquey motor with modern(ish) peripherals. The conversion’s not easy and Burwin motor cycles have told us it’s possible to get the same effect by lifting the ETZ’S barrel on a packer plate and machining the gasket face down. Resourcefulness is a key trait to long term MZ ownership!