XR500 versus XL500 rotor and stator

The rotor on the XR/XL is used to create a variable magnetic field and produce current through the stator coils.  It is also used as a flywheel with a significant moment of inertia to store and release rotational energy and smooth out engine pulses.  The more mass rotating at a given speed and radius, the more moment of inertia, the more stored rotational energy and the more “resistance” to acceleration or deceleration.  In other words, an engine’s smoothness at low RPM for instance (resistance to stalling) can be helped by a flywheel with more inertial mass.  Acceleration is also better controlled (less abrupt).  This thinking is reflected in the choice of rotor/flywheel installed on the XR versus the XL.  The XL model is mainly intended for street use with occasional off highway escapades — it thus has a rotor/flywheel with more inertial mass.  The XR on the other hand is intended for sportier use where engine acceleration is favored over low RPM smoothness and resistance to stalling — its rotor/flywheel thus packs measurably less inertial mass (see picture below).

XR500-48a
XR rotor on the left, XL on the right.  Note the visible difference in flywheel inertial mass.

The XR rotor weights 2.31 kg (5 lbs and 1.75 oz) whereas the XL rotor weights 2.96 kg (6 lbs and 8.75 oz).  The difference of 0.65 kg (22.9 oz) with a rotational radius of about 70 mm (2 3/4 in) is quite significant.  Swapping one rotor for the other will result in an absolutely perceivable change in engine character.  For this project I’m more interested in a very responsive motor than anti-stalling capabilities or smooth delivery of power and thus I’ll install the lighter XR rotor.

On the stator side, the XR and XL differ as well.  The XR is delivered with minimal accessories – no blinkers, no battery, no real world headlight, just an enduro interpretation of a headlight.  Its stator thus is a reflection of this minimal electrical power needs (see picture below).

XR500-54a
XR left side engine cover and stator.  Simple two-wire system, low power output.

The XL electrical system on the other hand includes blinkers, a real headlight and a battery which needs charging.  Its stator thus incorporates beefier coils which provide the necessary current to the bike’s electrical needs (see picture below).

XR500-53a
XL left side engine cover and stator.  Larger coils, higher power output.

I intend to keep the project bike as simple and light and possible and thus don’t plan on mounting blinkers or a battery — I’ll use the XR stator.  And if I change my mind, I’ll just swap the rotors and re-wire!

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3 Responses to XR500 versus XL500 rotor and stator

  1. H. Fritzer says:

    Hello Miki,
    Je pense que la visite de Roland ne va pas tarder, il veut que ton projet soit parfait:-):-)
    Gros bisous
    Mamie

  2. Paul says:

    Good day Mike
    Can you please tell me what colour the wires are on the xl left side cover stator. Also Can you maybe tell me which wire goes where on the bike I’m building a XR with a xl motor.

    • Mike says:

      Currently traveling and I won’t be back where the bike is for a while – I’ll look the wiring up and let you know upon my return.

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