Need help with lights

[rzsteve2]

I'm almost finished with my '84 RZ350 project of 20 years. Bought it from a guy that had converted it to full race mode and raced it. It had a title, so I figured it could be a killer street machine.
After many hours and money it runs great and I have a tag to ride on road. The last thing I left to do was the wiring for the lights. I hooked up the headlight, worked no problem. Since the frame was cut off at the rear, I can't mount stock tail light set up. So I bought one of those china aftermarket LED tail lights that have running, brake, and signal all with the two side by side lights. I followed instructions and referred to my Yamaha service manual and hooked up the wires. The running light worked, the brake light worked, but the turn signals would only come on solid light no flashing. So then I hooked up the front turn signals. They are smaller than stock, not sure if aftermarket, came with the pile of parts I bought with bike. Anyway I hooked them up, started the bike to check lights (no battery, get to this in a second), the front signal lights both lit up solid for a second then all lights stopped working. I immediately shut bike off. Now when I start the bike only the headlight has a very faint light. Reading the manual it says "never disconnect battery while generator is operating, if battery is disconnected, the voltage across the generator terminals will increase damaging the semi conductors". I don't know what I fried, but I have a feeling I ruined either the voltage regulator or the silicon rectifier. I bought a "battery eliminator" and installed it and still nothing worked but a dim headlight. I ordered the wiring to hook up a battery to then do some testing. I don't have much experience working on electrics. Does anyone on here have an idea of what may be the most likely to have failed? I would like to replace whatever the problem is before running the bike again. Thanks in advance. It's great to be back on this forum.

'85 RZ350N mostly stock, beautiful
'84 RZ350L project
'00 WR400F
'06 YZ250
'87 TW200

[silverstrom]

You need a solid 12 volts to run lights. If you remove the battery you absolutely need a battery eliminator (capacitor) to take the load or you will kill the stator, just as the book says.

If you do use a battery eliminator you will not have enough voltage at idle to operate anything that requires 12 volts. You need to keep the rpm up to get enough voltage to power the headlight, signal, horn, etc. That is the downside of not using a proper battery. In traffic you'll have no lights when you stop unless you keep the rpm high enough. Battery eliminators are great for racing, but I think they are a bad idea for a street bike, for obvious reasons.

Put a battery in the bike and try the lights, horn, etc. You don't need to start the bike. If things don't work on a fully charged battery you have work to do. If they do work on the battery start the bike and measure the voltage across the battery. You should see 13.5 to 14 volts at 5000 RPM. If you don't see anything close to that you have more work to do. Hopefully you haven't fried your stator. You'll need to swap out the regulator-rectifier to test it.

[rzsteve2]

Thanks for the advice. I'm waiting for some Yamaha battery leads, then I'll hook up a fresh battery and see what happens. I found a previous post that said measure the voltage across the battery and if it is way over then it is likely regulator failure. I'm hoping that if something is damaged this would be fairly easy swap and 150.00. A ruined stator would be more of a problem. The bike runs great so hopefully I can get it out on the road soon. Thanks for your help. I'll post what happens when I get the battery hooked up.

[silverstrom]

You can meter the stator while you wait for your parts. Very easy to do. Then you'll go forward knowing any problem is not a stator problem.

[kpke]

Check the white wires going into the connector from the stator. I did this repair fairly recently

https://youtu.be/oB-dXVCYIgI

The bike I am currently restoring has some melty wires at that connector also so will need some rework.

[rzsteve2]

The stator checked out fine, and I hooked up a new lithium battery. When I turn on the ignition switch the headlight burns bright and the tail light works as well. The problem is the brake light does not work. The light goes out when activating the brake switch. Tried two different switches, no difference. Horn, turn signals also do not work. I checked the voltage at the battery posts and it was right at 14 V at 2000rpm. So now I could ride it with a headlight and taillight, but no brake or signal lights is not safe, so I'm going to keep at it until I figure it out. Any suggestions as to where I should look next. The new taillight is aftermarket LED, and I bought a second one to test and it did the same. Would a LED light make a difference in this system? Thanks.

[tacky1]

Plug in the oem tail light harness and bulbs just to check. It might be wired different.
I know on a 500 the oil light won’t work with led tail bulbs for some reason.

[brrrappp]

FWIW
On my USA RZ350 the turn signals wont flash if I use bulbs with a watt rating that differs from stock yamaha bulbs.
There are common automotive bulbs that fit correctly but have a higher draw and won't flash.

[rzsteve2]

Thanks everyone that is providing me info. After checking and changing everything that I can see in the service manual it seems I might be onto something.
The test on the source coil, charge coil resistance on the low speed Br.-G wire test should be 225 ohms and it registers at 128 ohms. So I may have damaged the coil. Would the low speed resistance being damaged keep my lights, other than the headlight, from working?
My next step is to replace the coil with a spare and see what happens. My question now is my current coil and cdi is for a '85 (52Y-50), if I change over to my spare 29K-50 cdi and coil,
do I need to swap out the YPVS control module. My wiring harness has different connections for an 85 compared to the 84. In other words would it make a difference with a 85 ypvs control with
a 84 cdi/stator combo?

[JonW]

When you said 'coil' i assume youre talking stator... actual 'coils' are the same from LC through til 86 etc.

Well as you can use either stator and flywheel combo with both of those CDIs as you can rewire an early bike to that slightly later 52Y CDI etc. So just swap the stator as needed. you may need to create a flylead to make the connections but its not hard to work out.

The indicators are a factor of LEDs not having enough draw, you need a set fo ballast resistors and if using the OEM flasher as has been said you need to match the Watts, its very pernickity.

The brake is earthing the opposite way inside the tail unit i suspect, so the light is always on and youre switching it off. Also check both the switches are working as designed as one could be holding the light always on.