German Motorrad

Today in Motorcycle History

Kroboth Motorroller

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The Kroboth motor scooter - a vehicle with excellent road holding even at high speeds. After a 3-year trial period, it is now being mass-produced in the version described overleaf.

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The "KROBOTH" motor scooter was not built arbitrarily in the current form, but the findings of a long test period were evaluated. It is clear to every layperson that a scooter with the engine located under the driver's seat and all components such as the tank, spare wheel, luggage compartment and luggage rack completely relocated above the rear wheel cannot possibly have good driving characteristics, even at high speeds, on bad roads and slopes can. The whole weight is too far on the rear wheel, the engine has a rearing effect on the vehicle, especially when starting on inclines and the engine pulls heavily.

A 125cc engine with 4.5 hp is not yet as capable as e.g. B. a 175 cc engine with 10 hp to give the vehicle a high top speed and to cope with steep inclines at a good speed. So if a scooter has a powerful engine, it belongs in front, just like a motorcycle, as does the tank. As a result, you can also drive the scooter quickly without hesitation, you can cool the engine once or twice and achieve a quiet and safe road holding.

But a good scooter should not only be good on the road, it should also offer extensive protection against dirt. The body of the "KROBOTH" scooter is built in such a way that maximum protection is achieved. Equipped with a windscreen, the driver is completely protected and the foot position can be changed frequently thanks to the long rubber-coated running boards, so that unwanted fatigue does not occur. The foot shifter of the 4-speed SACHS motor is easy to use and you can switch to neutral from all gears without having to search by pressing the handlebars.

The simple airflow cooling of the standard models is perfectly adequate for normal conditions. The luxury models have double cooling, which guarantees sufficient cooling even in the most extreme cases.

With a "KROBOTH" - scooter with double cooling there is no overheated motor.

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Technical data of the "KROBOTH" - motor scooter 150 ccm / 175 ccm - models 1954 with Fichtel & Sachs - engines:

Chassis: tubular steel frame in triangular construction, stiff and torsion-free. Rear wheel suspension by swing arm via a leaf spring. Telescopic front suspension with fully bolted fork. Strong axles, running in 3 ball bearings, hub with 140mm brakes. Power transmission: by chain 1/2"x1/4" (150 ccm) 1/2"x5/16" (175 ccm). Unilateral suspension.


Length: approx. 1950 minutes

Width at the handlebar: approx. 700 mm

Height at the handlebar: approx. 900 mm

Saddle height: approx. 700 mm

Tyre size: 4.00x8

Engine Specifications (150cc)

Cylinder Bore: 57mm

Piston stroke: 58 mm

Cylinder capacity: 147 ccm

Compression: approx. 1 : 6.5

Continuous power: 6 hp at 4500 rpm.

Short output: 6.5 hp at 4500 rpm.

Top speed: 80-85 km/h

Fuel consumption: 2.4 liters / 100 km

Ignition system: Bosch flywheel magneto ignition 6 V - 30 W

Spark plug: M 225 T 1

Carburettor: F. & S. piston valve carburettor, 20 mm passage

Weight: about 120 kg

Load capacity: about 170 kg

Tank capacity: approx. 10 liters

Wheelbase: 1250mm

Climbing ability in 1st gear approx. 30%

Specifications of the engine (175 ccm)

Cylinder Bore: 62mm

Piston stroke: 58 mm

Cylinder capacity: 174 ccm

Compression: approx. 1 : 6.6

Continuous power: 9 hp at 5250 rpm.

Short power: 9.5 hp at 5250 rpm.

Top speed: 90 km/h

Fuel consumption 2.9 liters/100 km

Ignition system: Bosch flywheel magneto ignition 6 V - 45 W

Spark plug: M 175 T 11, for sharp driving M 225 T 11

Carburettor: BING - Piston slide carburettor 1/24/60 or 1/24/70

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Common engine data for 150 and 175 cc:

Transmission: 4-speed transmission

Clutch: 3-plate cork clutch

Gear shift: single lever foot shift

Equipment of the standard version (150 and 175 ccm) as standard:

Foam rubber double saddle - spare wheel - steering lock - electr. 25 watt headlight system with buzzer without battery and parking light - driving wind cooling.

Idle shift: by handlebar hand lever

Starting system: Kickstarter

Speedometer drive: from the main shaft of the gearbox.

Equipment of the luxury version (150 and 175 ccm) as standard:

Foam rubber double saddle - spare wheel - battery - horn - steering lock - parking light - double cooling.


Standard: (150 ccm) 1290 DM

Luxury: (150 ccm) 1490 DM

Standard: (175 ccm) 1380 DM

Luxury: (175 ccm) 1580 DM

Luxury (175 ccm) with electr. Starter (?) DM


Construction changes reserved

Here is the text of a flyer from the 1950s that explains the advantages of the Kroboth and especially the differences to the Vespa in an almost embarrassing way:

The KROBOTH motor scooter with a Sachs engine


As early as January 1950, the first motor scooters from the manufacturing company Fahrzeug- und Maschinenbau G. Kroboth in Seestall a. Lech.

Even the first test drives convinced the designer that a scooter with an engine under the driver's seat and the entire load on the rear wheel is impossible to reconcile with good road holding and high driving safety.

After a few months, therefore, the basic design, which is still being built today, was switched to, with the engine being moved towards the center of the vehicle, even as far forward as possible. The tank was also given its place at the front. It was already clear back then that the ever more powerful engines would also make the scooter faster and faster, and even then the manufacturer took the view that motorcycles up to around 200 ccm would sooner or later be completely replaced by scooters. So if you combined the good properties of a motorcycle with the advantages of a scooter, a vehicle was created that not only offered good road holding even at high speed and bad roads, but also extensive weather protection. At the same time, every woman had to be able to drive the vehicle and the individual parts of the machine had to be easily accessible, although the dirt that comes from the engine had to be kept away.

If you look at the chassis of the "KROBOTH" scooter, you will notice that the rear wheel, which is sprung with a leaf spring, is completely free for the two drivers. No engine or tank weighs heavily on this bike. Imagine a scooter with the engine under the two drivers' seats, including the tank, spare wheel, the two drivers, luggage and a steep incline with the engine pulling heavily, which is also trying to lift the front of the vehicle .

Even a layman can then imagine how much driving safety is still available and what the steering ability of the front wheel looks like. With the "KROBOTH" scooter, the weight ratios are the same as with a good motorbike. During the test drives in 1952, we also drove up the Turacherhöhe. This steepest alpine road in Europe has a gradient of 32 percent. With man and luggage we drove up and stopped in the middle of the steepest climb to try starting. It worked, the excellent Sachs engine picked up again even here and although most people have no idea of ​​a 32 percent incline, one didn't have the feeling that the machine could roll over backwards when driving up this outrageous incline. When we drove our souped-up test machines on the autobahn at more than 100 km/h, we didn't have the feeling that driving safety left anything to be desired. Yes, one thought unconsciously that it could actually go even faster. Of course, such things only apply to test drives. It is easy to guess how much calmer and safer such a scooter is at a normal speed.

Based on all the tests and measurements, rides and test constructions, the manufacturing company decided on the vehicle form that is shown to you today with the "KROBOTH" scooter. This construction is far more expensive than that of known constructions. But today's construction and shape offers the possibility to drive quickly and safely even with powerful engines.

So if you have other shapes in mind for a scooter, consider whether you would do better to follow our explanations or whether you think that such considerations do not have to be made if you value protection and driving safety.

Starting from the pursuit of good road holding of the scooter, was first a short wheelbase (1250 mm), a rigid, torsion-free tubular steel frame was created, which also completely absorbs the stresses that occur and completely relieves the bodywork. The frame consists of a tubular steel triangle construction, which is fully stressed in tension and compression, and since one side of these triangles is always bolted, no stress can arise from welding. So if you take a good look at the chassis, you will see this principle everywhere.

The rear wheel is sprung via a steel swing arm and a leaf spring, the front wheel has a telescopic fork of our own design. This fork is fully dismountable and built with high security. The hubs each have three strong ball bearings and are built in such a way that a long service life can be guaranteed even under the highest loads. Only with this hub design is it possible to hang up the wheels on one side with maximum safety and to be able to move when changing a wheel like in a car, i.e. simply unscrew the wheel bolts and reinstall the spare wheel in the same way. In the event that you want to repair the tire yourself, provisions have been made so that you can do this safely without any assembly tricks. The wheels are made in two halves, so after loosening the screws, the casing and tube can be easily removed without risk of damaging the tire or tube.

Anyone who has ever had to patch a motorcycle tire will appreciate what it means to be able to easily swap wheels. This advantage is only possible with one-sided wheel suspension (like with the car) and only with the scooter, with its small wheels. How and where do you want to take a spare wheel with you on a motorcycle?

The hubs built with three ball bearings have 140X20 mm brakes, which easily brake the vehicle. even when running at high speed.

Above all, the body is constructed in such a way that the driver has the greatest possible protection against the wind and dirt on the road and the machine. Your shape was also designed so that z. B. the front part aerodynamically derives the driving wind well and presses the machine against the ground at high speed. With the shape of the "KROBOTH" scooter, the legs can also be placed as far forward as the wheel lock allows. This is not possible on a scooter with a straight leg shield. In terms of aerodynamics, a straight leg shield is not exactly impressive, especially at high speeds.

When driving with a windscreen, the front part of the "KROBOTH" scooter is designed in such a way that the driving wind is kept as far as possible away from the driver. But there is another secret in this front piece. It intercepts the low-lying cold driving wind so well with its inner funnel that the "KROBOTH" scooter actually doesn't need a fan. All the air that is intercepted by the almost 700 mm wide funnel sweeps over the engine without the driver noticing it. Nevertheless, the engine of the luxury models has a fan that cools the engine sufficiently even with a tailwind and in low gears. The double cooling of the "KROBOTH" scooter is the best guarantee for a long service life of the engine.

The tank, which holds about 10 liters, is also installed in this front part. Most other scooters have much less tank capacity and it is not pleasant when you have to fill up too often, and especially not when you can fill up less than 5 liters. Every tank cap is more or less leaky and leaves behind oil residues with the two-stroke mixture, which can be very unpleasant if the clothing comes close to the tank cap. The tank cap of the "KROBOTH" scooter is therefore located at the front of the vehicle in such a way that any fuel residue that may flow out drips off so that the driver does not come into contact with it.

The headlight, the horn and the steering lock are also in the bow. However, this bow is not riveted or welded together, but is screwed together from two parts, so that in the event of damage, each individual part can easily be repaired.

Provision has also been made to ensure that the vehicle can be supplied with a strong, chrome-plated bumper on special order. This is rubber-mounted and largely protects the body in the event of a fall and prevents damage to the frame because the rubber mounting absorbs the impact. The speedometer, which is driven by the gearbox, is installed in the tank that is lying on the floor in such a way that it is easy to see.

The center piece covers the engine like a tunnel and can be removed completely after loosening four nuts, like the hood of a car. This allows repairs and maintenance work to be carried out on the engine without dismantling the entire body. Such repairs can also be carried out without removing the engine or dismantling the body.

The center piece is very low, so that ladies are not hindered when riding in skirts.

The petrol tap is positioned in such a way that the stranger cannot easily find it and the insider can access it without any problems. If you want to get to the carburetor or the candle, all you have to do is open the cover built into the center piece with one hand. So you don't have to remove this center piece first, such as for repairs or maintenance work.

On the rear part of the scooter, the foam rubber double saddle is mainly built up, which can be folded backwards, revealing the tool box and the cover, which makes the battery accessible. The battery is also made of polystyrene, a transparent material. Therefore, you can check the acid level without dismantling, which is so important for the service life.

The side parts of the rear structure are also attached with screws and can be removed just like all sheet metal parts of the body. All sheet metal parts are shielded with rubber profiles to avoid vibration or friction and keep the body quiet at any engine speed. Long running boards (1300 mm long and up to 180 mm wide) make it possible to change the leg position at any time while driving and the strong grooved rubber provides a secure hold. The step plates are so long that two suitcases or plastic panniers can easily be accommodated without hindering the driver. Special luggage bridges can also be supplied on request.

Switching is done with the left heel. By stepping on the lever, the gears are shifted down, e.g. B. from fourth to third gear. With the heel you push the lever up, whereby the gears are shifted up, e.g. B. from the second to the third speed. So that you don't have to search for neutral by pedaling up and down for a long time, there is a neutral lever that makes it possible to switch to neutral from any gear from the handlebars. You then start the machine and shift through to first gear by stepping on the shifter. Then heel the lever through to fourth gear as needed. The automatic shifter works in such a way that each time you push the shift lever up or down as far as possible, one gear is shifted at a time. The power is transmitted via a strong motorcycle chain, which runs completely encapsulated in the steel swing arm. From the swing arm to the engine, the chain is largely protected against dirt by the mudguard fitted under the engine. Of course, the chain on the rear wheel hub can be tightened easily. To do this, remove the rear wheel, loosen the 6 hub nuts and tighten the chain with the screw provided. (Don't stretch too tight!)

The protective plate just mentioned under the engine largely prevents the entire machine from getting dirty. Without this sheet metal, the dirt thrown up by the front wheel is heavily thrown into the engine tunnel and damages the entire machine.

The lighting consists of a 130 mm spotlight with 25 to 35 watt lamps. These only burn with great uniformity when the engine is running, with the tail light burning, of course. The superfluous charging current is charged into the battery via a rectifier built into the headlight. The engine only starts when the ignition key is inserted. By turning the key to the right or left, either the parking light *) or one of the two main lights comes on. Switching from high beam to low beam takes place away from the handlebars.

The electric horn *) (no buzzer) also only works when the ignition key is inserted. The tail light and the number light are combined with the prescribed reflector. So if you remove the ignition key and lock the steering lock, maximum security against theft is required.

The stand is constructed in such a way that you do not have to lift the machine. This is particularly difficult for women.

Only on luxury models. (We reserve the right to make design changes.) Equipment and prices see brochure

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