MZ 32mm Teleskopgabel

MZ 32mm Teleskopgabel

Step 1: Check for ovality and adjust if necessary.

Step 2. Cool

Step 3: Warm threaded collar

Step 4: Unscrew collar

Bing 84 carburettor spring-retainer

Take one piece of suitable square tubing (19 x 19mm).

Going on holiday in Great Britain

In the beginning ...
Day One, 0 miles

The Twa Brigs or Third over Forth
Day One, 140 miles

Reading
Day Two, 600 miles

Day Five, 990 miles

Day Five, 990 miles

Day Seven, 1000 miles

Day Seven, 1000 miles

Day Seven, 1000 miles

Day Eight, 1120 miles

Day Eight, 1180 miles

Day Eight, 1190 miles

Day Eight, 1230 miles

Day Eight, 1250 miles

Day Eight, 1290 miles

Day Nine, 1330 miles

Day Nine, 1370 miles

Day Ten, 1390 miles

Day Ten, 1420 miles

Weymouth
Day Thirteen, 1610 miles

The last Mod in Dorset
Day Thirteen, 1620 miles

Carter Bar on the A68
Day Fifteen, 2130 miles

The Eildon Hills
Day Fifteen, 2150 miles

The Athens of the Central Belt
Day Fifteen, 2200 miles

The Davidson Legacy Cottage, Angus
Day Fifteen, 2280 miles

Walter Kaaden's disc valve racers and the Australian Engineer

Motorcycle Engineering

Phil Irving

Each chapter of this book is based on an article written for the English magazine Motor Cycling and originally published in the 1950s or early 1960s under the pen-name of Slide Rule. Phil Irving worked in England for Velocette and Vincent. After returning to his native Australia he designed the engine of the successful Repco-Brabham G.P. racing cars.

I have extracted the material on MZ two-stroke racing engines designed by Walter Kaaden. Taken from the Clymer Publications/Speedsport edition; 5^th reprint; 1973.

I have added my comments in italics. Louis Mair  
 

Fin Design p. 181

Fin Effectiveness   p.194

… Nevertheless, there is obviously good reason for locating the exhaust at the front, or if this is not practicable, at the rear rather than at the sides, as is done indeed on the M.Z. two-stroke. Considerable lengths have been gone to in this engine to reduce the pick-up of heat in the exhaust-ports; although there are two cut in each cylinder, they  merge quickly into a single outlet, the length from bore to flange-face being less than two inches (Fig. 10.19).

Central-drive Twins   p.203

Recently, it has become a trend in racing design to construct tiny twins as two individual single-cylinder engines attached to a central component containing the primary drive and (in four-strokes) the drive to the valve-gear. This is of particular advantage for cooling in such designs as the 250 c.c. M.Z., and is still useful in the case of a four-stroke, though to a lesser extent ...

 

Inlet Port Control   p.247  

 

   This objection is overcome by the disc-valve which is used in the MZ and, no doubt, is part of the reason why the 125 c.c. model can turn out power equivalent to 170 b.h.p. per litre (Fig. 13.5).
    The valve itself is of sheet steel, 0.020" in. thick, and rotates in a space only 0.040 in. wide. It is not mounted firmly on the mainshaft, but is driven by splines so that it can centralize itself in the gap or move to one side or the other, so acting like a reed-valve during the closed periods. The periphery is cut away to open the port, which then has a

… Units have been made with just a pair of gears … if all the ratios in the box are indirect-as in the M.Z., for instance- … the engine rotates “forward”, so that a single pair of primary gears is suitable.

Basic Unit Layouts   p.315

… With a transverse four-cylinder engine, excessive width would be created if the drive were taken off one end of the shaft. … On the Rondine … taking the drive from the centre of the shaft …

GEARBOXES AND TRANSMISSION                   319

There has been a tendency in recent years for English designers to adopt what might be termed "semi-unit" construction. In this system, a flat face is machined on the back of an otherwise conventional crankcase and bolted thereto is a gearbox which has a mating surface machined on its front face. The rear half of the chaincase may be cast integrally with the drive-side half of the crankcase, as in the B.S.A. twins,* or it may be a separate bolted-on component.

In this construction, there are no shear loads...

Although at first sight it does not appear to do so, the 125 c.c. M.Z. utilizes this built-up principle, but in conjunction with an all-indirect gearbox and cross-over drive, which results in a neater and stiffer unit than would be obtained with both drives on one side.

*Early model BSA A7/A10/Kawasaki Commander with bolt-up gearbox and primary chain tensioner.

 

TWO-STROKE POWER                                  250

THE KADENACY EFFECT

It was at one time held that high power could not be obtained at high speed because of the short port opening time available. But actually the reverse is the case--it is precisely because the times are so short that full advantage can be taken of pressure-waves in the exhaust system and what is known as the "Kadenacy effect" to get the high outputs previously thought to be impossible.

٭ Kadenacy found, by ingenious experiments with a special engine, that if the exhaust ports were large and opened with sufficient rapidity the imprisoned gas would rush out at such high velocity that it continued rushing out until the port was closed again, by which time the pressure in the cylinder had become sub-atmospheric. It follows that if another valve, which may be a port or may be a poppet-valve, is opened at the right moment, enough fresh mixture may be drawn in to enable the engine to keep running without the aid of crankcase compression. But if crankcase compression is present, this effect obviously assists the entry of mixture from the transfer ports, though at the same time it has a tendency to suck a portion of this mixture out through the exhaust, as there may be a depression of 5 or 6 lb./sq. in. present in this port, immediately after the discharge of the main body of gas.

٭ Kadenacy is an adjective derived from the name of Walter Kaaden  [see Mona's comment below]

Exhaust Waves

By using a short, open pipe this negative pressure wave can reflect back as a positive wave that promptly rams some of the lost charge back into the cylinder, with a marked increase in power at the appropriate speeds. It has since been discovered that so far from needing an open pipe, it is better to use an expansion chamber with a restricted outlet, when the desired wave-effects will be intensified. A curious fact is that the outlet area may be less than that which would normally be provided on a touring machine developing about one-quarter of the power; that on the 250 c.c. twin Adler racer, for instance, is only about 5/8 in. diameter.
Representative port timings for an engine designed on these lines are: exhaust opens (and closes) 80 degrees from b.d.c.; inlet opens (and closes) 68 degrees from b.d.c. The top edges of the exhaust ports should be square to the axis in order to achieve a strong Kadenacy effect in the blow-down period of 12 degrees thus provided.
The trouble with these engines is the old one of lack of flexibility. Maximum power may be in the region of 9,000-10,000 r.p.m., but when there is little useful power available at a mere 2,000 r.p.m. less, when the resonant conditions upon which the high power depends cease to exist. Nevertheless, a lot may still be learnt by a modified application of this principle to sports engines.
An interesting recent development aimed at spreading the power over agreater range is the "boost-port" system devised by J. Ehrlich* (Fig. 13.6). In one form, two small booster

 chambers, lying between the transfer and exhaust ports, are first filled with fresh mixture through "window" ports cut in the piston below the bottom ring. Further movement of the piston seals off the chambers which then discharge their contents into the cylinder when their openings are uncovered by the piston a few degrees before b.d.c. This is a variant of a system used on the M.Z., in which a third port is located between the two transfers and opposite to the exhaust. This port is the opening of a booster-chamber which is filled via a window-port in the piston, the resulting flow of cool mixture helping considerably to ventilate the interior of the piston in which little gas movement normally occurs.

٭  Dr Joe Ehrlich lived in England where the press frequently wrote about him as a two-stroke engine designer. A German-speaker, originally from Austria, Ehrlich organised with Kaaden a form of technology transfer. Kaaden secretly gave Ehrlich old design work in exchange for racing parts he could not afford to buy. 

Eclectaride In Blue

Preface

[To the Repair Manuals for the MZ Motor-Cycles ES250 and TS250; translated from a German original by Druckhaus Aufwarts, Leipzig.]

Eclectaride in blue at The Albergue Montesa

© Albergue de la Montesa 2012

We hold lengthy comments on MZ motor-cycles to be unnecessary. In the high latitudes of Finland and, in the parching heat of Africa, under the most different operating conditions these motor-cycles run to the satisfaction of their owners.

Eclectaride in blue with MC Pistón, Cantabria

To ensure that the vehicle remains in perfect working order and reliable in service after a long period of operation, involving a certain amount of wear, we issue this Repair Manual to give the necessary instructions to our MZ-Workshops at home and abroad.

Eclectaride in blue in the hills of Cantabria

© qwert malone 2012

Repair work is a matter of confidence in several respects:
      Reliability and workmanship of the mechanics; the safety of the driver depends on them.
      Finding the actual cause of the trouble; this ensures that no material is wasted and labour costs are restricted to a minimum.
      From these items result: no retouching work, short times of inoperation and low repair costs.

Eclectaride in blue in Castro Urdiales



A good workmanship in repairs largely depends on the use of the special tools and means recommended by MZ. We should like to underline that especially self-service workshops and amateur constructors should bear this in mind to avoid considerable additional etpenditure of labour und material due to false avoid considerable additional expenditure of labour und material due to false optimism.

Eclectaride in blue with a cat, Bilbao

Our MZ-Workshops may purchase the special tools from the MZ Spare Sales Department  -  for home-mechanics, however, there is only the possibiliy of constructing them with the help of the sketches given in a supplement to this booklet.

Eclectaride in blue with a cat, Aberdeenshire

We hope this Reference Book offers the required information to the staffs of the workshops contracted for servicing our products at home and abroad, and to the friends of MZ motor-cycles throughout the world; and we wish good success to each and all.

VEB MOTORRADWERK ZSCHOPAU

Betrieb des IFA-Kombinats Zweiradfahrzeuge

Abt. Kundendienst