Yamaha Y20

I got it working now. bought a new battery, and the battery has the wires built on it to connect to bike. Ground to rectifier mount screw, positive bullet plug to rectifier. Why do I need a "half wave rectifier', now? Are they more efficient? Just get one from a newer bike?

I think i figured it out from the pictures/ parts schematics, on the link he sent me. It shows the battery positive hooking to the fuse from the rectifier. When I got this bike, the fuse from rectifier was plugged into the yellow coming from motor going to ignition switch. As the yellow is the charging wire , It looks like it is made to plug in there, when there is no battery available .

It is close, so it did help. Mine is a Y20 though, for sure. A bit differant from that YJ2, Tailight assembly and a few other things. Thanks.

Hi Looks like an early YB100 from what I can see - in which case you may well not find a negative connection for the battery as it would go straight to earth on the frame. Not sure about the bike in general but if it like the YB then it will run a magneto system for starting and charging - the battery is only a 'backup' for keeping the electrics (lights) running at low speed, so maybe it didn't have a battery? Sorry can't help more than that. REPLY>>> I think you are right about the battery being a backup to run lights. As I can not use it at night, the mag does not put out enough to run lights and turn signal, or brake light at same time. It is a 80cc Y20, but I am unsure of exact year.. The grounding wire for the battery is not there, and seems to be no place around the battery box to connect one to ground. It has battery hold down hardware in the battery box, but no extra wire connections anywhere to connect to a battery.

I have what I believe to be a 1964 model Y 20 Yamaha. It has a spot to mount a small 6 volt battery. But the is no wires there to hook one up. And I can not see were there used to be any wires that have been disconnected. It is in great condition, and everything looks very original. So I am baffled why no battery connections. Does any one know about these little bikes? Wiring diagram? How to ident exact year? Y20 864554