CZ`s & MZ`s and all that

[truslack]

This thread needs more Jawa-Velorex outfits


https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-ash4/323676_10150536423331028_1260516113_o.jpg

Or jawa's without chairs

https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-snc7/s720x720/298404_10150325582596028_819145400_n.jpg

and my CZ (most of it at least)

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-snc6/247479_10150193451861028_4359700_n.jpg
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Current: Suzuki RG 125 Gamma, Honda H100, Triumph Tiger 800XC, Suzuki SV650 (minitwin)

[moonzoomer]

some pics of a few I owned in the 1990s, the pics are old so the quality is poor

a quite rare (in U.K) Cezet 250 cc single cylinder with the older style teardrop crankcases, the forks are the same as the 350cc Jawa twin with alloy wheel rims.
https://i1142.photobucket.com/albums/n604/mawlarky/MVC-332S.jpg

another rare eastern bloc bike , a Tula 200 that I bought after the Berlin wall came down brand new for 400 quid. The bike has very wide tyres front and rear (10" wide approx), the engine is a 200cc dynastart fan cooled Sachs type motor which is started the same way as a car by inserting the key and turning.
https://i1142.photobucket.com/albums/n604/mawlarky/MVC-331S.jpg

one of my Jawa 350cc high back combos, I toured Ireland on this one with zero problems bar a front wheel puncture covering 2.3 k miles over a 2 week period, these high back outfits have a seat that coverts into a bed easily for overnights without the need for a tent, this particular one eventually had one of the exhaust downpipes rerouted through the sidecar for heating.
https://i1142.photobucket.com/albums/n604/mawlarky/MVC-333S.jpg

[moonzoomer]

A better pic of a Tula 200 cc found on the net
https://i1142.photobucket.com/albums/n604/mawlarky/tula_1312375159.jpg

[moonzoomer]

another eastern bloc oddball I came across in the early 90s which has since been restored, the Scooter is a Hercules Prior 200cc 4 speed manual clutch and uses a very similar sachs engine to the Tula 200cc with 12 volt electrics and dynastart. Must have been quite a bit ahead of its time for a 1959 bike compared to british bikes. Note the twin high level fuel tanks mounted behind the cast alloy front of the bike and the treble expansion chamber silencers. the engine is fan cooled via cast alloy ducting which in turn heated the riders legs.

https://i1142.photobucket.com/albums/n604/mawlarky/MVC-334S.jpg
https://i1142.photobucket.com/albums/n604/mawlarky/MVC-335S.jpg

[Teflon-Mike]

[RhynoCZ]

https://i970.photobucket.com/albums/ae184/RhynoCZ/649880_3.jpg

Well, what do you think?
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[pepperami]

Interesting? more please
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I am the sum total of my own existence, what went before makes me who I am now!

[Zen Dog]

[Teflon-Mike]

[stinkwheel]

[RhynoCZ]

The engine is definitely Chinese.

I think they've got contract with TMEC.

This is a picture of Jawa 125 Dandy, people here say that it's alright cheap machine for every 16year old rider or as a commuter.

EDIT: Link to an specs and photos: https://www.jawa.fi/model.php?lang=en&model_id=4 (randomly picked on google, but it's in english, so don't worry.)
____________________
'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Old Tearaway]

Being amongst probally a very small exclusive club of people who've managed to do the "Ton" on Czech made 2 strokes I figured I should write in after a friend pointed this post out to me.

A pointer first..... All Jawa and CZ motors have the power output restricted in various ways. For example:

1970's CZ 125-476 and 175-477 models are fitted with along metal induction load device (has the same effect on the motor as a human trying to run wearing a gas mask) to limit engine output power and limit maximum under load RPM. The only other manufacturer to use this was Honda on the MBX50 where removing it gave an extra 8 MPH above the 30 MPH stock exhaust system restricted top speed.

This pipe is visible with the carb rubber removed or by looking down into the plenum under the airfilter. Removing it requires total dismantling of the airbox. On the CZ 175 power is increased from 14.5 HP to close to 18 HP at the rear wheel as the engine can now rev higher and the powerband width isn't curtailed. The original 1960's CZ 175 club racer, from which the engine originates, prodcuced 19.9 HP.

The other restriction method employed on all CZs is the under saddle intake silencer. Handy if fording a river up to the bottom of the gas tank in depth but a considerable load on the motor breathing. Best modification is to cut the backs off of the airbox lid tubes.

Numerous theories abound as to the reasons for CZ restricting the CZ 125 and 175 singles but the most likely is that they didn't want it to out perform and out speed the Jawa 250-559 and Jawa 250-362 Californian, not to mention the Jawa 250-623 Bizon and later CZ 250-471.0 the latter having adhoc and very poor port timing as it is derived from the Jawa 350-633 Bizon motor.

However having a smaller capacity model out performing the 250 in production never saw Honda restrict the CB125T or CB200 both of which were better and faster than the CB250T and CB250N.

In 1986 Jawa released the 350-638 which produced 34 HP @ 6,500 RPM at the rear wheel. These are easy to spot because the rev counter doesn't have the green band and the redline is set at 7,000 RPM. The motor also sounds like a YDS7 350. The motor featured 4 well angled transfer ports and larger single unbridged exhaust ports.

In 1989 the engine was restricted by reducing the piston skirt cut outs by 25mm. so that only 2 of the 4 transfer ports opened at BDC. The exhaust system on the bike was shortened and a large exhaust choker was placed on the baffle end. This gave the bike 25 HP at the rear wheel, less than the 28 HP and 38 Foot / Pounds of torque Jawa 350-634 it had replaced.

Why?? In order to make the bike compliant with the kill joy authorities of Austria (where the RZ350YPVS is restricted to just 27 HP and runs 20mm. carbs!!)

For Holland the carb manifold featured additional restriction in the form of acarb manifold choking gasket to further restrict the power to 22 HP to comply with the country's capacity / power output laws.

On the commuter Jawa 350-632 models only the exhaust baffle choker is fitted and is easily removed to restore the 28 HP at the rear wheel.

One interesting feature of the exhaust choker collar on the baffle is that with the bike in neutral and the throttle held wide open the bike will never exceed 5,500 RPM.... pretty effective restriction, eh??

Removing the internal engine restrictions requires mechanical skills beyond most of today's bikers. Not as bad as with the Austrian market Yamaha RZ350YPVS which requires the cylinders being replaced (I know somebody who brought one into the UK) but still requires advanced knowledge and understanding of 2 stroke motors.

With Jawa and CZ bikes it sn't as much as tuning them, it is undoing OEM power restriction devices.

The bike CZ should have built was the CZ 350-472/638 with the full power 34 HP motor. They didn't but others have done so as cafe racers. Whilst just about capable of pushing past the "Ton" in the 361 Pound Jawa frame, in the 291 Pound CZ twin frame it is a lot faster. It will easily push over 110 MPH and on the version I built back in the early 1990's I managed to push it close to 120 MPH with the rev counter touching the redline at 7,000 RPM.

The motor need 5 gears and has all the problems that the Suzuki 250 T-10 had with it's 4 speed gearbox when tweaked, as does the CZ 250 when tuned up. Stretching 4 speeds to cover a wider speed range in order to prevent over revving the motor in top gear is a problem.

Back in the days of leaded 4 star petrol, which had a higher energy content than today's modern ethanol crap, the CZ 250-471.1 was clock through timing lights at MIRA at 85 MPH both ways by BIke Magazine. The earlier CZ 250-471.0 was only capable of 74 MPH when it was tested.

The CZ 250 featured thicker cylinder walls, as it used the Jawa 250-623 Bizon motor, which itself was a modification of the successful Jawa 350-633 Bizon motor. However the port timing and cylinders are not scaled down 350 types but are unique to the 250-623 motor. At high speeds, because of the design of the cylinders and the thick walls, the inner surfaces heat up quick and if speeds over 75 MPH are forced for more than a minute or two the motor will nip up (after fair warning). Being a Jawa CZ motor no actual damage, apart from the rider's soiled underwear, happens.

If the motor is bored out to 307cc and fitted with 350 pistons the problem doesn't exist, just like it doesn't exist on the 350.

In 1974 the fledgling Aprillia assembled CKD CZ 125, 175 and 250 machines in Italy so that CZ could avoid Italy's protectionism foreign imported vehicle taxes. Honda did the same.

The CZs produced in Italy had to contain some native parts so the wiring, sealed beam headlamp, pistons (Asso Werke high compression forged), brakes (Ferrodo AM-4), etc. were OEM on these models. Motors were built with Japanese Koyo low friction coated bearings. The Aprillia CZ 250-471.0 is far faster and better performing than the Czech version and will push 90 MPH on a good day.

As CZ didn't yet produce a 350, Aprillia built their own in the shape of the CZ 350-471.0 which used the 350-633 / 350-361 Californian crank with caged roller bearings and Asso Werke high compression forged psitons. This is the only road CZ model that will do the "Ton" from the showroom (I own a 80,000 mile one and compared to the stock Czech version it is fast and sounds different).

It was fitted with TLS drums front and rear.

Problems with it are just a few and surround the results of the engine's increased power output..... it stretches and snaps the right hand chain adjuster with regularity unless modified with a high tensile bolt. The other is the stresses it puts on the engine mountings.

I've found that derestricting the 22 HP Czech built CZ 350-472.1 to 28 HP at the rear wheel by bypassing the restrictive air intake system results in similar problems. The frame is not very happy with being exposed to 38 Foot / Pounds of torque @ 3,800 RPM over time. This is probally why CZ restricted the motor to 22 HP.

At high speeds the frame handles no different than at the manufacturer's expected top speeds regardless of the powerplant fitted. Brakes work fine with no fade ever, especially if fitted with EBC Gold kevlar ceramic shoes (worth the money).

Oddly enough in 1973 the CZ 250 was originally going to be powered by the 250-988 MX / Enduro motor and 4 examples were built by dropping a 250-988 5 speed motor into a CZ 175-477 bike. Then they tried the "not for sane riders" CZ 400 MX motor and it destroyed lighting and a few other parts during testing. It was intended for export but instead they decided on building a bike using the 16.5 HP high torque (when measured against Japanese 250cc 2 strokes) low revving Jawa 250-623 Bizon motor..... the rest is history.

(Yes the CZ 250, CZ 380, CZ 400 and CZ 500 MX motors will drop into a CZ 250 / 350 road frame, for the insane cafe racer builders amongst you!!)

The only Czech produced "Ton up" machine was the 1980 CZ 350-472.4 faired Custom (Sport) Mark.III. which used the Jawa 350-631 motor and could hit 101 MPH. Only 6 were built to order at Motokov GB, so I'm informed, and I've owned one since the mid 1980's though I blew the motor up after it digested a gearbox selector fork at 35,000 miles near Reading. I ran it on a stock 350-638 motor after that but it wasn't the same.
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Since the EU ban on brand new 2 strokes enjoying the experience of a powerband surge on a motorcycle are becoming a exclusive priviledge. I feel sorry for today's young riders stuck with boring 4 stroke singles.

[jjdugen]

Tuned CZ 250-471 circuit racer in New Zealand. (It is actually overtaking the 350 Manx Norton!!)

Think that's an NSU Sportsmax, 250cc
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The CBR900RR has been sold. Aprilia Falco worms its way into my heart.
Try Soi 23 on Amazon for a good read.... Self promotion? Moi?

[lingeringstin...]

I've done a lot of experimenting with MZ engines. I worked at a bike shop when people were literally giving MZ's away because nobody wanted them so we had an endless supply of bits and as a courier on an MZ people kept asking me to collect the dead MZ's from their back yards for my spares and I ended up with quite a pile of stuff, so why not experiment?

In standard form the 12v MZ 250cc engine turned out to be the cheapest courier engine I could run because it was primitive and had so few moving parts, not even reed valves, and all the bearings and seals were bog standard off the shelf parts that could be had anywhere. That was the good thing about the old communist design.

The bad thing about those engines was that they were terribly undertuned and most Japanese 125's were faster, but that also meant the MZ engine was fairly long lived as a courier hack. Old blokes like to say that MZ's "go on forever" but the fact is they didn't go on very well at all until you rebuilt them with proper bearings and seals.

The old MZ pistons were prone to breaking with minimal abuse but by the middle 1990's cheap Malaysian knock-off pistons were better than the standard MZ ones and quite cheap.

Basically once an MZ engine was rebuilt properly with decent bits they were pretty good engines as far as reliability, and that was great for courier hacking and you could double the fuel economy by fitting a standard Jap carb.

In fact pretty much every part of an MZ motorcycle is made better by throwing it away and replacing that part with a non-MZ part, and a lot of my bike is no longer MZ.

As far as making them compete with Japanese performance I did get them to go over a hundred mph with a lot of jiggery pokery but they never lasted very long tuned like that. Nowadays I make my 250 engines good for about 75 at a push and get 80-100 mpg and they last quite well, but pretty much any 125 would do that these days.

The MZ bike on the whole is much heavier than an equivalent horsepower bike (about 20hp in bog standard form) and they generally handle appallingly so in all pretty much any modern 125 would do what an MZ 250 does and do it much better.

HOWEVER...

Mine is now tax exempt, cheap insurance and I can fix it with a rock and a hammer, and I like that. It's still a miserable bike but I've grown used to it and kept in reasonable fettle it's always dependable and I could load it up with camping gear and go virtually anywhere without worry, at the breakneck speeds of a mile a minute all day long.

[RhynoCZ]

[Old Tearaway]

When compared to the influx of Chinese bikes which are made of strange materials such as Crapite and Shiteium 90 (after 90 days it turns to s**te), pre-rust impregnated steel frames, plastic bodywork that warps in direct sunlight, valve heads that melt / detatch from their stems, unhardened mild steel gearbox cogs, nylon bushes where bearing should be on transmissions, etc. people are just starting to realise just how damned good and reliable the old Eastern Block bikes really are.

Where as your average Chinese made bike is rarely likely to reach its first MOT test, old Eastern Block bikes have dozens or more under their belts.

Spares support is better than excellent too.

This is why prices are going up for Eastern Block motorcycles..... they last forever.

To quote a 1970's CZ advert poster in the US,

"Most motorcycles are built to last a few years. Our motorcycles are built to last for generations".

I ride around on an 80,000 mile plus CZ 350 occasionally and most of the time on a 1977 CZ 250 still on the unrebuilt factory stock motor.

Let's face it, Jawa, CZ and MZ bikes have outlived their so called superior Japanese equivalents. Proves some kind of a point doesn't it.....
____________________
Since the EU ban on brand new 2 strokes enjoying the experience of a powerband surge on a motorcycle are becoming a exclusive priviledge. I feel sorry for today's young riders stuck with boring 4 stroke singles.

[smegballs]

I had an ETZ 250 and I did love it, though it was complete shite.

Every 1500 miles (almost on the dot) the points would "slip" for lack of a better word, reducing the bike to a 25mph limp. This was cured by resetting the points gap, then it would be fine for another 1500 miles.

The mechanical voltage reg repeatedly shat its pants, boiling batteries and blowing bulbs.

The bike was generally "unreliably unreliable", it didn't even have the decency to be reliably unreliable. You'd try to go to work in the morning and it just wouldn't start, then a few days later, with nothing been done to it, it would happily burst into life first kick.

The helix gear type arrangement for the clutch-pusher was annoying to get re-assembled with the proper indexing after removing the kickstart-cover.

Water would run down the clutchcable and straight into the gearbox, contaminating the oil.

I did like it, and would like to get another one someday to play with in the garage and tinker with: homemade voltage reg and infra-red ignition for example. As a means of transport however, mine was useless. I gave up on it eventually and went back to my 125.

[RhynoCZ]

UK ads from the 70's... (not sure if posted before) That was pretty much the best time to buy a CZ, nothing new/better came from the factory past this point.

https://i970.photobucket.com/albums/ae184/RhynoCZ/Everything%20else/303796.jpg

https://i970.photobucket.com/albums/ae184/RhynoCZ/Everything%20else/303795.jpg
____________________
'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Old Tearaway]

Yep, the vibration free, smooth running CZ 250-471, capable of 85 MPH with the rider prone on the gas tank and running on leaded 4 star was replaced by.....

.....the CZ 250-485 with the mid 1960's CZ 250-475 trials bike motor.

Some say that it was CZ's attempt at creating an MZ 250 as it was slow (70 MPH), vibrated like anything if ridden hard and was cheap.

I have one sat in the garage.

Good points are the handling, reliable electrics, very torquey motor and lacks the ugliness of an MZ.

Bad points are that ON / OFF back brake, worst fuel consumption than the 250 twin and the vibration.

They do make great trail and trials bikes, which is what happened to most of them.

It did manage to take the title of slowest 250cc bike on UK roads away from the Honda CB250N Superdream (83 MPH eventually) but lost this to Kawasaki's Z250C Custom (67 MPH flat out) soon afterwards.

A friend of mine had a Voskhod 175 for 27 years. It never ran despite everything being apparently set up. I even took a look at the thing, having a reputation for raising anything two wheeled from the dead. I did manage to make it cough and that was that.

It was very economical as it was pushed in attempted bump starts for tens of miles during its life. Brakes were good for the 5 MPH speeds attained during push start marathons, with speeds of up to 20 MPH (in neutral) down hills.

As an extra bonus it kept all who attempted to start it very fit and was good for burning off calories (about the only thing it could burn off!!)

Not totally safe as heart attacks were possible during push start attempts.

As for MZ voltage regulator, what Jawa CZ rally would be complete without an MZ turning up with electrical problems.....

Were they made in Italy by any chance??
____________________
Since the EU ban on brand new 2 strokes enjoying the experience of a powerband surge on a motorcycle are becoming a exclusive priviledge. I feel sorry for today's young riders stuck with boring 4 stroke singles.

[stinkwheel]

[lingeringstin...]

[Oldie]

Had some great rides on my 350 earlier in the year until the throttle cable snapped. Installed a new one but put the jet needle on the wrong setting when re-assembling the carb and couldn't start it. Took it off again and did exactly the same thing . Shoved the bike into the corner and it's sat there ever since.

https://lh3.googleusercontent.com/-DkoZEjPJGns/VMuiDbHMS_I/AAAAAAAAEXI/JRm91sqtDXI/s800-Ic42/003.JPG

[ojelun]