It dawned on me today just how amazing and wonderful the Internet is when it comes to troubleshooting mechanical issues. If I'm having an issue with something chances are somebody else somewhere down the line has had a similar issue.

My R1 developed an interesting malfunction today. When I apply the brakes (front or rear, while it's running or off) it kills the power to the dash. As soon as I release the brakes power cuts back on the dash as if I just turned the motorcycle on, all the lights light up simultaneously. A quick look over on the Yamaha R1 forum and I discover this is a pretty common issue and now I have quite a few possible culprits. Short, main harness, bad ground, bad v reg, or bad battery.

Thanks to the help of the Internet I've been able to pretty quickly narrow it down to a few things that could be causing the issue. It's reassuring to know this is a issue somewhat specific to this vintage R1 and with some luck I should have sorted out later today. This would've been a bit harder without the inter-webs help.

It really is amazing that we've gone from the Dewey decimal system at the library to having the Internet in our pockets in just the last 20 years.

You're right. There's a video or tutorial for just about anything at our fingertips. A few more clicks and the parts are on their way overnight.

Despite the many challenges society faces, it is a great time to be alive.

The battery took 5+ hours to charge. The issue disappeared with a charged battery. Now to figure out what is draining the battery.

what's great is that for the moment bikes are simple. don't need a fancy diagnostic machine to work on them (exceptions of course for late model BMW's, etc.).
The actual wiring diagraphm a human can understand in the service manual.
Brakes hit the electrical system in only two places so this is easy.
Have fun.

Sounds like the voltage regulator is not charging the battery.....could also be a bad ground.

Remember trying to find dirty magazines without your parents catching you when you were a kid?

The internet is wonderful

Sorry, I know nothing about motorcycles. Just had to point that out.

Fault Finding Guide

I'd start with the link above with a close eye on the connection coming from the regulator/rectifier. Yamaha has a bad problem of restricting electrical current flow with their white connectors instead of giving it what it needs. Also, on a bike as old as yours, age will be a factor on all connections. Moisture and other crud inside an electrical contact point will make it corrode. Might be time to look at replacing some of those connections with Weather Pack Connectors. R/R Connector Kits Everyone seems to like their products and they have connectors for just about any application.


Also, do a Current Draw Test . It might help you see where your electrical vampire is if you have one.


Hopefully you find the culprit and get everything tip top! Good luck.

The battery is reading at 14.3 volts when the bike is not running but turned to the on position (headlights & dash are on and it is ready to be started). It charged for over five hours yesterday. Is that voltage normal?

That's a completely odd voltage and way above what's possible for a 12v wet cell. Is your meter ok? Or is there something unusual in the battery box?

Yes, the internet has made working on cars and trucks a lot easier.

Conversely, cars and trucks were a lot easier to work on before the internet.

Ah... the old days. Where the biggest problem you had working on a car was reaching the engine.

14 v DC is normal to me. I would caution against thinking too deeply on the battery draining. My mosikle battery was measuring fine one day and bad the next. A new AGM battery may be all you need, even though all the forum wisdom is also correct. The Honda Interceptor wiring harness and charging gizmo were both defective by design, and had to be replaced under warranty, so these things do happen. But, it may just be the B+.

Ok. Brief update. I think the R1 is fixed. So now would be a good time to sell it before something else breaks.

I spent a few hours chasing down and cleaning grounds and every connector I could reach. I installed a new voltage regulator and the bike appears to be charging its battery now. While running it is reading around 13.2-13.8 volts. The dash still dims (only noticeable at night) when I hit the brakes but it isn't cutting off anymore. I unplugged the rear brake lights and the issue disappears. I'm not sure if the dimming is normal. Maybe a LED tail conversion would draw less juice and make this issue disappear completely?

LED conversion will require that you have a converter in between the 12V and the LED bulbs, while the bulbs themselves draw little power, you still have to connect to the stock system, also you turn signals may or may not work without a module/converter inline as led's don't return a signal to modules they are working and the module (stock) thinks the bulbs burnt out and you get fast flashing lights.

I would look for a bad wire, rubbing and grounding on that circuit.

Does the brake light switch energize a relay?

If the brake lights and dash are on the same circuit then installing a relay and separate wire from battery through relay to brake lights may fix the dimming