I know this has been beat to death, but here goes anyway. I have 12+ volts going into the rectifier, but only about 2 volts at 5,000rpm coming out.  I have a new battery and an LED taillight bulb on the way. A new rectifier is certainly in order. A rectifier/regulator would be ideal. I tried the search and have looked over a lot of post on this, but still need some guidance. Does 'DEET' have the best part? Anyone else?

Thanks in advance. I really appreciate it.

Dave

Normally you'd only use a plain rectifier which is still available from Yamaha.  It's just a heavy duty diode.

Regulator is used on the AC headlight circuit.  It's AC only.  No rectifier.  Your bike didn't come with a regulator but it's wise to install one.

The above is tried and true.  Other arrangements might work.

Also without knowing your testing method it might not be the rectifier at all. 

To test, I just used A VOM on A/C to test the input to the rectifier and then D/C to test the output. The input would actually go past 12 volts above 4,500rpm. But I could barely get 2 volts output even above 5,000rpm.

Is there a thread on this already? I tried the search and leafed through quite a few pages of posts and didn't find a comprehensive thread on this. I bought a CT-1 new and had a lot of problems with the lighting system on it. It went back to the dealer a couple of times for blowing headlights and such. After a few months, we just pulled the lights off and made it off road only because they couldn't resolve the issue. Had I known that the lights were going to be such a problem, I would have bought an MX.

Thanks for the help.

Not sure about your test methods but i'd put a volt meter across the battery & see if it gets up past 6 volts. I actually used to test amps by running the battery earth through my old yamaha test ammeter which is easy to see when its on the right side of good & by how much with increasing revs. Easy to watch how much individual things like flashers & brake light draw & if the mag is putting out enough to keep up with it. That's in the days before regulators--just rectifiers. With the headlight on you can get more charge to the battery by running the lowest wattage headlight you can get away with but with sealed units in the US its not practical to experiment like us here with replaceable bulbs. Weakest wattage headlight bulb gives a brighter light on a mag system but too weak & it'll blow out as can't stand the volts or something like that. Also don't run a starter through the ammeter but you're talking 6 volt i'm thinking so no heavy draw. By memory there's a double connector on one mag loom wire where the--something--green i think can go to the yellow double to give the battery heaps in lights 'off' mode during the day.

Reading Mark's and RT325's replies (both really helpful, as always!), sounds like you might well need a 6v regulator and a rectifier.

As RT says, put a volt meter across the battery and see what you're getting.

Shame about the issues with your CT1 - Yamaha produced a subsequent Service Bulletin acknowledging this problem (see Tech Library) and showing how the regulator should be fitted.

Battery is at 1.9 volts. Doesn't look too old, but I have a new lead acid one on the way in case this one is bad.

Okay...  the battery is like a crude "regulator" on these bikes.  If it's bad it can definitely cause your low charging voltage issue and can damage other parts (including smoking the rectifier) so best to not run without a good battery..

 

Here's the bulletin for you.
www.yamaha-enduros.com/index.php/service...e-voltage-regulators
If you can get the slightly smaller Yamaha regulator then you have more location options.
Here's some examples of what a few of us have done, take your pick.
www.yamaha-enduros.com/index.php/forums/...44-voltage-regulator

Very good reference material. Thank you. My new battery came in today. It's charging now. When it's charged, I'll swap it in and see if that perks things up. But I suspect that the rectifier is shot. There are a couple of different styles on Ebay from the same seller. Any experience with either one of those?

I also pulled the notes from my old RT-2 with the same problem. I did not add a regulator on that bike. I replaced the headlight bulb in that one with a 12v fog lamp bulb. Worked good enough for day driving which is all I do. And I never had to replace it. When I get the LED taillight bulb, I'll see what I've got and go from there.

Thanks again and I'll keep posting as I plug along.

I run 12 volt snowmobile bulbs in 6 volt systems and have had no issues to date. They are bright when rpms are high like driving down the road.