So it looks like I have had the wrong dynamo on my M20 since I bought her 14 years ago !
Its not putting out anything so decided to take it off and bench test it.
Its an E3HM which I presume is a short bodied one...what were these originally fitted to ??
It wont motor when powered up, just makes a small click but wont spin. Brushes look good.
Whats my next move ??
Strip it clean the gunge out check for free rotation, clean brush contact surfaces, give it a bit of a spin in the correct direction of rotation when attempting to motor, then stop and try again, fail to run now, check coil,manual has a section on it, do easy bit first,
If your bike is not used for a prolonged period of time, the field coil can lose its residual magnetism. Flashing a dynamo can be sufficient to kick it back into life. Make sure that you flash it to the polarity of your bike's electrics (i.e. positive or negative earth).
Stripped and cleaned. Lot of rust on the armature surfaces and the field coil plate.
Very minimal output on the bench test, so put it back on the bike anyway.
Started her up an on medium idle its pushing out 7-8 volts so it must be spinning fairly fast (my elec hand screwdriver is fairly slow I guess)! Which sounds good to me. Just hope the regulator is up to it now !!
Richard.