Sachs motor kit

This is the Sachs-engined Mongoose comfort bike I commute on. Sachs sold off it's division that makes this kit, a German bike company called Hudson now manufactures it, and there is a Taiwanese clone (many parts are interchangeable) called pro-Rotary. It complies with restrictions that apply in Europe, Australia, and I believe Canada, that primarily dictate 200W max output, which is about what an average person can produce. But as we all know, not all the time! 200W gets you about 30km/h.


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    Spartamet motor 1.jpg
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  • Sachs bike 1.jpg
    Sachs bike 1.jpg
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nice ride,i like those motor wheels,my friend has a briggs 1.3 horse from 1950 something,wow really great to see this:eek:


Yes, its cast, it comes as an integral part of the motor system, its available in 20", 26" or 700c. The gearing's unchanged though, so the 20" would be slower at the rev limit, although it'd have more torque. The hub of the wheel is a drum brake because the rim isn't machined, so v-brakes can't be used. The gearing and wet clutch run in an oil bath that's a separate part of the crankcase. The whole system is well developed and reliable. Part of the exhaust can is a torque arm that you can see running forward almost to the bottom bracket. This bike has a 3-ring chainwheel that's the only pedal gearing, but it can be set up with a five-speed derailleur, although it would be redundant. I'm in top most places, the two lower chainwheels only get used on steeper and REALLY steep inclines, where the motor slows to about 15 km/h and just a little pedalling keeps it there.


Hi Motorkit. Mine is a Sachs one, known in Europe as a Saxonette or Spartamet. Sachs doesn't make them now, a German bike company called Hudson bought the rights and tooling, still calls it a Saxonette. There are two or three Taiwanese made copies, McLee/Forsen and pro-Rotary are two brands. I don't know where they can be bought in your country, but they're widely available in Europe, Asia and Australia. Specs: its 30cc, rated at 200 Watts and has an ignition limiter to limit the speed to 25 km/h, which is a legal requirement in Europe. It develops 200W from 15 km/h up, with a decompression valve that limits the power as revs rise. Because the speed limit in my state in Australia for motorised bikes is 50 km/h, I replaced the ignition with a generic coil from a line trimmer. With the speed limiter ignition, it gets to 25- 27 km/h then misfires to keep it slower. Without that ignition, it will rev up to about 32 km/h, firing cleanly. Even with the derestricted ignition, it only revs to about 4500 rpm tops, which keeps it pretty quiet. The design is a system, really. You replace your regular rear wheel with the cast one teamed with the motor, reduction gearing, and the rest. It's got a wet clutch, I've done maybe 4000-5000 kilometres since I bought the bike secondhand on ebay, and the clutch is still as good as ever. It weighs about 8-9 kilos that add to the bike.
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hi zumer. i have the same motor. Do you know how to put more oil into the gearing? How would i remove the rev limiter? would you be able to post some pictures of the electrical system that you have set up? Can ijust take out the ignition thing so it goes faster.?


I would be careful about taking out the rev limiter as that can lead to turning your engine inside out very suddenly and having to walk home :eek: