Shifter777,
Definitely negative earth. The Fuse is built into the Positive (red) wire to the battery. It is a little unusual.
The Selenium Rectifier often becomes leaky and doesn’t perform well as it ages. Switching to a bridge rectifier works but it changes the charge behavior as the Selenium rectifier and the silicone rectifiers have different voltage drops. There had been some pretty lengthy discussion of this over on the S90 Yahoo Group which migrated to another hosting service. I saw bits of the thread which went on for weeks. (I do not joke about that either) as the guys who are on the S90 group are super knowledgeable about the S90 and the old Yahoo C70 group has a similarly sage group of enthusiasts.
I have a Nov ‘69 build S90 (CS90) that was a US Serviceman’s bike from Japan most likely. I picked it up in ‘08 from a lady in El Paso and it still had the titled from Washington state. The TX lady had it fitted with big knobbies and had been using it off-road in the dirt in TX...
It is unusual in that it has the EPA headstock plate indicating the build month and year as well as being compliant with US EPA regulations in effect at that time and the Serial number being on the headstock as well as on the side of the Tbone frame below the ignition lock... I has the ruby red metallic paint and chrome fenders and turn signals...
Different bike and I love the style of these little “tiddler” bikes
The small Honda motorcycles are a blast and a step back in time...be they the C70 or the beautiful lines of the S90.
David
