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Swinging Arms

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One of the more significant, yet least noticed, design changes from ES to TS models was the swinging arm mounting. ES models employed a composite solid bush that was lubricated (via grease nipples) by oil or grease through holes drilled in the swinging arm spindle. Owners rarely remembered to do this, causing wear, creating play, resulting in the need for new bushes to be fitted.

The ETZ swinging arm is basically the same design as the earlier TS and later 251 or 301 versions, but of beefier construction. It is a good idea to fit an ETZ swinging arm (retaining original wheel, 16" in TS cases). Especially for use on outfits.

Tensioning of Swinging Arm Bushes (19K) MZ employed torsioned rubber bushes on later models because they are effectively maintenance free and should last the life of the machine. The way they are torsioned makes the swinging arm self centring, the bushes also reduce road vibrations being transmitted to the frame, so making for a more comfortable ride.

Rubber mountings are soft and can give so a means of stopping lateral swinging arm play is required. MZ used washers either side of the swinging arm to eliminate side play. The two inner washers abut against the frame and an outer washer behind each spindle end nut. The theory is, the inner washers between frame and swinging arm bushes can't move, the outer washers between swinging arm bush and spindle end nuts cannot move laterally but can deflect vertically.

It may also be noted that although the swinging arm bush inner is supposed to move with the swinging arm the spindle is not. If however, the inner does seize onto the spindle, the spindle can "rock" with the swinging arm movement. With the amount of maintenance that most swinging arms get this spindle will no doubt be seized in the frame as well. In this case (most cases, to be honest) the spindle cannot move because its seized in the frame, the bush inner cannot move because its seized on the spindle so swinging arm movement is accommodated by the rubber bush deforming with the swinging arm movements. This bush is not supposed to work like this (the swinging arm becoming effectively spring loaded) but can cope with it. The extra force of the spring loading works the shock absorbers harder as well, promoting overheating of the shock's oil and hence "fade" of damping. i.e. a bouncy ride.

Cross section of worn swinging arm washers The first point to note is that the three swinging arm spindle washers control (or reduce) lateral play in the swinging arm. They wear, and once grooved create play, allowing lateral movement (any lateral play is an MOT failure, for good reason).
The second point to note is that there are two bushes, and each bush should have two washers (four in total). MZ for some reason have only fitted three! I think it's a mistake nobody has noticed (or was bothered about). I always fit four.

The reasoning is, the nut on the side panel end of the spindle can "eat" its way into that end of the swinging arm bush, it offers little or no resistance to the lateral arm movement, a fourth washer here and a suitably tightened spindle should eradicate virtually all play. This is true assuming the four washers are not worn, they should be periodically replaced. Few people replace these washers, but is a good idea to do so.

A stainless steel replacement spindle is a good idea, but not stainless steel washers. These being harder than mild steel and will wear the swinging arm bush outers requiring their replacement. Far better to replace four (cheap) mild steel washers periodically.

Cross Section of Swinging Arm Bush Removing seized in spindles can be somewhat troublesome (massive understatement!)
Start by removing the centre stand spring (TS and ETZ) and the two spindle end nuts. Use a good quality 27mm spanner on the spindle nut below the side panel and attempt to turn clockwise. This will give an indication as to how easy the job will be, if it rotates easily it will just tap out, five minutes tops. If it is rock solid it will be a war of attrition.

Lubricate liberally with a good quality penetrating oil, over night or a period of days will be best. Try turning the spindle (clockwise only), there is no point taking the nut off (it's not supposed to) or stripping the spindle. If the spindle moves so far and stops, lubricate liberally tap back and turn, turn, tap back and forth until the spindle is out. Two weeks next Saturday. . .


Using heat will damage the rubber bushes in the swinging arm, rendering arm effectively scrap. More importantly the nitrile bushes become Very Toxic when heated, and they will poison you.

Many thanks to Derek "Slip" Alker

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