Sachs motor kit

Discussion in 'Photos & Bicycle Builds' started by zumer, Dec 18, 2007.

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  1. zumer

    zumer Guest

    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.

    Attached Files:

  2. Sianelle

    Sianelle Guest

    Nice :grin: Is that a cast alloy wheel on the back of your bike?
  3. beast775

    beast775 Guest


    nice ride,i like those motor wheels,my friend has a briggs 1.3 horse from 1950 something,wow really great to see this:shock:
  4. Alaskavan

    Alaskavan Guest

    That does look like a comfortable ride.
  5. zumer

    zumer Guest

    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.
  6. MotorKit

    MotorKit Guest

    Hi Zumer,
    I'm from Argentina and I love that engine. Where can I found it? Who's the reseller? Can you give me more info?
    See you on :D
  7. zumer

    zumer Guest

    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.
    Last edited by a moderator: Dec 21, 2007
  8. lancem

    lancem Guest

    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.?
  9. Sianelle

    Sianelle Guest

    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 :shock:
  10. kenspice

    kenspice Guest

    Last edited by a moderator: Dec 23, 2007
  11. jgarrish

    jgarrish Guest

  12. srdavo

    srdavo Active Member

  13. Sianelle

    Sianelle Guest

    Corker video :grin:
  14. OldPete

    OldPete Guest

  15. Hive

    Hive Guest

    Free Wheel

    It seems obvious, but I have to ask, is it possible to ride free-wheel?

    From what I see, if one does not wish to free wheel, this might be "the" best engine yet.

    Out of way, small, enough speed, simple.

    I like it very much.
    Last edited by a moderator: Jan 31, 2008
  16. Lemsteraak

    Lemsteraak New Member

    Hey Zumer,

    I've been playing with these little Sachs engines and actually have a couple. The old ones with the head and cyl together, airplane style I understand were made by Moto Morrini in Italy for Sachs. These are really sweet. It has the decompression valve and everything.

    My wife liked my bicycle so much she wanted one, so I got a new engine from Sachs, before they went bankrupt, and this one was the Chinese built one with the separate head. It doesn't run nearly as well, so I swapped the carb and ignition module, no change. It is noisier and slower. Do you know if this is normal?

    Oh, a little insight into the engine, Sachs has built models of these beginning in the 30's, but went bankrupt last year. There was a cash infusion from a Chinese company and now Sachs is back. During the bankruptcy, the Dutch importer and Hudson somehow managed to get the rights for the engine and the Saxonette name. Sachs now has virtually the same bike that they renamed the "little Saxy".
  17. luke

    luke Guest

    original saxonette kit

    hope you don't mind me posting pics of my original 1930s sachs saxonette kit.i do have a more modern restricted one with a dodgy automatic clutch which tends to stick.

    Attached Files:

  18. Hive

    Hive Guest


    Amazing! And equally amazing the thing was not melted down...!

    Will have to check the moped in my garage. If it is a Sachs, might have another project in the future.
    Last edited by a moderator: Feb 1, 2008
  19. Sianelle

    Sianelle Guest

    That's amazing alright, - I didn't realise that the design was so old. :shock:
  20. Lemsteraak

    Lemsteraak New Member

    Hey Luke,

    Very cool engine, has a nice early German look to it, kind of a art nouvieu thing going. I would love to see one running with the old engine.

    I know a little about the automatic clutch on the new Saxonette engine, they are very clever, the clutch is actually in the crankcase. This way the intake from the carb cools the clutch and helps to keep it from overheating. I don't have a good answer to why it is grabbing. The simple things to look at are your idle speed being too high and possibly your two stroke oil. You might be able to get a better take up with a synthetic, they lubricate better so may give you a little more slip and maybe a little better for the engine.

    Oh, got news that the Dutch importer (Brittijn) got upset with Hudson because of supply issues. They have suspended their agreement. These engines are apparently very difficult to get right now. Take very good care of your Saxonette.