KZ750 B1 Regulator\Rectifier in one unit -> readjusting

Hello all, this is my first( of many I guess) posts as I've almost finished to restorate an old 1976 Kz750 B1.
My charging circuit wasn't working so I've replace the regulator\rectifier with a YAMAHA one (see pic) and it's working pretty well.
The only downside of this readjusting is that the field coil has become a permanent-on unit (brown to 12v, green to earth), as the regulator only work on dissipating the extra current, not by stopping\limiting the field coil as the original one does.


I was also considering to not drain the battery when the engine is not running to attach the field coil after the engine run switch so it will be powered only when RUN is selected.

I've read a lot on this forum in the past days but I haven't found a solution like this, do you think this may work on a long term or there is something I am no thinking of?
I noticed almost every time the solution is to buy regulator\rectifier from oregonmotorcyclepartsoregonmotorcycleparts and honestly they looks great, but at the moment due to covid and to shipping costs and time to deliver to Europe I would prefer to use a different solution.

Thank you for this great and super helpful forum.
Merry christmas all the way from Italy.

That is a very harsh way to get the charging system to work. The filed coil is not designed to have full power on it all the time, and then you are wasting any excess charging power as heat.

It would be much better to get a functioning field-coil regulator.

The early 750 twins used a very unique regulator system not found on any other Kz. The unique thing is that the regulator is solid-state and controls the negative side of the filed coil in order to regulate the output voltage. Most other Kz's that use a field coil have a mechanical regulator to control the positive side of the field coil.

You can reconfigure the polarity of the field coil wires and get a solid state regulator for an early Kz400 twin, or a 1977 Kz650. They use the positive-field-coil-control.

Or you can wait and get the proper one from OregonMotorCycleParts.com.

Or you can maybe adapt one from an old car like an old Ford.