Motored cycling in Sydney, Australia.

Discussion in 'General Questions' started by zumer, Dec 15, 2007.

  1. zumer

    zumer Guest

    I'm new to these threads, and I've been reading about the uncertain and inconsistent legislation that you poor buggers have to deal with in the US. When I first got to thinking about a motorised bike, I rang our Roads & Traffic Authority and asked them what the law allowed me. The criteria here is:
    200W max.
    50cm³ max.
    50 km/h max.
    Apart from that, no limits, no exception clauses for gearboxes or whatever.
    Most gas engines are rated at more than 200W max., but they only produce more at higher revs. In Europe and other parts of the world, the restrictions are similar to ours, except that they generally limit top speed to 20 km/h or 25 km/h.
    After considering this, I bought a Sachs motor that's built into the rear (cast, not spoked) wheel, it's been sold for a few years as a "Spartamet", and is pretty well known in Germany and Holland. It's pretty quiet, generates 200W from 15 km/h up (above that speed, a decompressor arrangement between the exhaust and combustion chamber lowers the effective compression ratio, and as a result, the power), and from the factory, has an ignition system that limits the revs to 3750 rpm, 27 km/h. It's good reliable transport, but my daily commute is 40 km each way, uphill and down, and I could only manage to average about 22 km/h. After I'd used it for a while, the ignition system croaked. I went back to pedals only and public trains while I thought about how to handle the repair job. European sites offered derestricted ignition modules that claim to allow the bike to rev out to 35 km/h or so, but there was the cost, the time, having to assemble an electronics kit, and all, so I finally just tossed the ignition system away entirely, discovering that an ignition coil from an old Ryobi string trimmer I had to hand would fit on the laminations of the OEM coil. What a difference! Previously, at 27 km/h, the motor would stutter and fart, as the plug didn't spark on every stroke (which must've been responsible for a few additional unburnt hydrocarbons being dumped to atmosphere), now it doesn't. It'll rev out cleanly. I broke one of the sensor wires on my speedo, so I haven't actually measured it's speed yet, but based on my commute, it's now averaging 28 - 29 km/h, which is only a very little slower than getting through peak hour gridlock in a car. I do wear all the HiVis I can so that I'm safer through visibility, and the local police here wave to me, and wave me through stuff sometimes. Thanks to whoever here in Oz that saw fit to propose sensible legislation, and to the rest of the legislature for seeing the sense.
    I'm now working on a bike that's similar to the setup that Daton offers, with a pocket bike engine, except instead of the Daton gearbox, with the CVT belt transmission fitted to some pocket bikes, and a cogged belt drive rather than a chain. I'm thinking I'll probably have to at least partly enclose the belt to prevent pebbles getting wedged between it and the drive cog, and I don't think that standard spokes will cope with the weight and power, because they're breaking with just me providing the motivation. I went to a local sports store where they were offering a yummy Mavic downhill rim and hub with thick, straight spokes, but the wheels are $350 apiece, so I can only admire them from a distance. I may end up getting another cast Sachs wheel and using that, they're about half that price, and trouble-free, except it has an inbuilt drum brake, or I could adapt a disc brake. Rim brakes won't work with them. Maybe I should think about those five-spoke cast rims that're available, except I worry about the rigidity of the rims with that few spokes.

    ps. fergot to mention with all of that is that no registration is needed, 'cos it isn't a motor vehicle!
    Last edited by a moderator: Dec 15, 2007

  2. fabphil39

    fabphil39 New Member

    I have a "Rotary" brand engine that I believe is very similar to your Sachs. See:

    I also am trying to make it go faster, and was under the impression that it only needed an after market CDI unit. Is this the case, or do you think I'll need to replace the whole ignition system? I haven't found these European sites but then I haven't been looking under "Sachs". Any help would be appreciated.

  3. zumer

    zumer Guest

    The Rotary units look very similar to the Sachs, certainly the ignition, gearing and general arrangement are near identical, but the barrel and head are separate on the Rotary, and it doesn't appear to have the decompression valve that the Sachs does. I'd also given some thought to the aftermarket ignition module kits that are offered, but I needed sparks in a hurry when the original system died. I used what was to hand, which was a Ryobi coil from a line trimmer. ANY coil that'll fit will do. I took the original coil off the original laminations, and the Ryobi coil off it's laminations. There's an earth lug that needs to be separated from the laminations to do so, some are screwed, some are spot welded. The spot welds can simply be drilled out, then the hole drilled through into the Sachs laminations and a short self-tapper used to make the connection. The orientation of the coil doesn't matter, any way it'll fit will do. The Ryobi needs a bit of resin ground away where the spark lead enters the coil, so it'll fit within the Sachs case. I connected the original plug lead to the Ryobi one with a fencing staple, a leg through each lead, then the joint wrapped with insulation tape. All this sounds involved, but to me it's less involved than assembling electronics, with no guarantee that the new module will be more reliable than the old, even discounting that I assemble it right. BUT, doing away with the ignition module simplifies the ignition, so I'd expect better reliability in the longer run. Don't expect to be matching the motorised traffic once it's done, the Sachs is tuned VERY softly, so it doesn't need a cooling fan, but that being said, the Rotary units are offered in the US rated at 500W rather than 200W. Perhaps the difference between the two models is simply the ignition cutout. On level ground, without wind, my Sachs tops out at about 31-32 kmh.
    I've been intending to do a pictorial step-by-step of what I did to the scoot, but I'm just flat-out pressed for time from pressure of work, so it'll be done when I can manage it.
    Last edited by a moderator: Feb 24, 2008
  4. Lemsteraak

    Lemsteraak New Member

    Hi Zumer,
    Sounds like your ignition is spot on. Both the Rotary and Sachs use a CDI ignition with a separate ignition box (ignition module). I don't really understand the electronics either but I do have a schematic drawing and instructions on how to make one up. I guess the idea of the separate ignition box is so they can tailor the power to comply with the regulations for each country. Germany I guess is very strict and really limits the power and speed.
    I blew up the ignition box on a Rotary engine I had. It was loading up so I swapped to a non resistor spark plug, bad idea, the ignition box gave out. So, the ignition module is very touchy and your solution sound much more robust, you don't have to use resistor spark plugs. Let me know if you would like the schematic and I'd love to see what you did, when you have time.
    Oh, the decompression valve that you refer to I don't believe limits the speed or power. You probably noticed that there isn't any compression when you pull the starter rope. It may be different on your Rotary but on the early Sachs engines, the decompressor only works when you start. They don't have to put on a very powerful starter motor if there isn't any compression on starting.

  5. fabphil39

    fabphil39 New Member


    Hi Rich,

    I would love to have a look at those schematics and building instructions. Maybe you could post them?
  6. Lemsteraak

    Lemsteraak New Member

    Give me a couple days, the instructions are in Dutch so I'll work on a translation for you

  7. Lemsteraak

    Lemsteraak New Member

  8. fabphil39

    fabphil39 New Member

    Sachs 301 CDI.

    Fantastic, :grin: thanks Rich. I'll have a go at building this circuit next weekend, and post the results here.
  9. Lemsteraak

    Lemsteraak New Member

    I'd really like that, I've been meaning to build one myself.
  10. fredie

    fredie Member

    so what happened:smile: