Aftermarket CDI module

Discussion in 'General Questions' started by Unregistered, Feb 17, 2008.

Tags: Add Tags
  1. Unregistered

    Unregistered Guest

    Hi All,

    I have a Rotary brand hub engine kit that I bought a few years ago. When I bought it the dealer said it was possible to increase the speed of this engine by substituting a different CDI module, because the standard module limits the motor speed. (though he couldn't recommend this since it would put the power output over the legal 200w limit, and void the warranty).

    The distributors in Australia:
    Say in defense of their product: "ROTARY'S INTERNALLY GEARED HUB MOTOR IS NOT GOVERNED, it is NOT CAPABLE of more output without EXPENSIVE internal re-engineering." Presumably this "expensive re-engineering" means replacing the CDI module.

    Well, the warranty ran out some time ago, and I'm looking to increase the speed of my motor.
    Has anyone heard of this before? Does anyone know where I can get one of these modules?

  2. kerf

    kerf Guest

    Man, thats a neat bike motor and somewhat expen$ive. I just did a forum search (rotarybike) and found a couple of threads. One post said the ignition module contained a rev limiter but another said the intake ports were the limiting factor. I don't know, have you done a search? Better still join and start a thread in the General Discussion forum and see what pops up.

    Good luck.
  3. Jim H

    Jim H Guest

    I don't know where or what type of cdi you would replace with but yes, I have heard of some chinese scooters that are restricted through the cdi and are derestricted with an aftermarket performance cdi. That's all I have.
  4. fabphil39

    fabphil39 New Member

    Hi All,
    I originally posted this as Unregistered, and KERF suggested it might be a good idea to join up and start a new thread in general. I have tried searching the 'net to no avail so I'm hoping for some word-of-mouth input.

    Here goes:

    Thanks in advance, Phil.
  5. fetor56

    fetor56 Guest

    I don't think it can be done Phil.Correct me if i'm wrong but their is no governor on this engine...the speed is restricted by the placement of the ports themselves so even if u get a better CDI/carby/whatever,your performance will remain relatively the same.
  6. gone_fishin

    gone_fishin Guest

    fetor, i restored yer reply as relevant. i've been told the operating "frequency" or whatever can have an effect but have yet to see or hear anything concrete about this. i don't think it's a question of "better" maybe, but "different"...?

    a ps about the ports: can port-timing itself really be a "ceiling?"
  7. loquin

    loquin Active Member

    to keep themselves out of hot water with the Australian government, which limits engine output to 200W for assisted bikes that don't require registration, the company line would HAVE to be that the engine is not easily modifiable to produce more power.

    I've seen reports that it IS the CDI module which is the power limiting device for this unit.

    It is very similar in appearance to the Morini FM128, a 1 HP (apx 750W) drivetrain.

    One way to potentially test this would be to remove the spark plug, then drive the wheel externally, so that the wheel ground speed would be greater than 20 MPH. If the engine is cdi limited, you should be able to see the results in the spark. It should start dropping out.

    I've seen reports that cdi limited motors start 'missing' as the bike speed approaches 20 MPH.
    Last edited: Feb 18, 2008
  8. fabphil39

    fabphil39 New Member

    Watch this space

    When riding with the throttle fully open, it seems to actually go slower than if you back off a bit. The engine also sounds and feels rougher. So I think it may well be the CDI that is limiting the speed.

    I've not had any luck with my searching, but have found a link to a Vintage Motorcycle CDI electronics project which dates from 1975. (the simpler the better) I plan to build and install this, and will publish the results here. So "Watch This Space".
  9. kerf

    kerf Guest

    Good for you, go for it but remember it may not surrender without a fight. We learn through failure so if the first try goes down in flame, toss it aside and start over. Good luck.
  10. Watcher05

    Watcher05 Member

    There was a similar post on here and the poster was saying that he swapped over the CDI unit with a Ryobi (or similar) CDI unit from a weed eater/weed wacker. Said the improvement was really good. He was from australia and it was one of the hub style motors. Maybe do a search and see what comes up.