Generator wont kick in until 1500 rpm's.

[Mart]

I've been looking at the charging on my 33. It's running 12V. I fitted a generator made up from what I thought was a later 12V generator with an 8ba style front plate and pulley.

I have tried two different regulators, and the generator does not pull in until 1500rpm.

I cleaned the contacts on the regulators and the generator, and cleaned the commutator and brushes.

Could it be that the generator I thought was a 12V unit could be a 6V unit?

Is there a way of telling if an armature is for 12V or 6V?

How about the field coils, is there a way of telling if they are 6V or 12V?

I have tried rigging separate grounds from the generator and regulator to battery ground, with no effect so I presume the existing grounds are ok.

Any ideas?

FWIW my roadster starts charging at just above idle, I don't have to rev it to get it to pull in.

Mart.