Bizarre tachometer/electrical issues

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Jave · #1 Unread post by **Jave** » Fri Sep 11, 2009 2:15 am

I have some electrical issues with my bike but I'm not sure if this is related or not. The problem is my tachometer will almost never reset itself to 0. When you turn the ignition on, it's supposed to do a self test go from 0 rpm to redline and back but instead it does weird back and forth motions and comes to a stop at random rpm values. Wherever it stops becomes the new 0 and the tach will rev up from that point. Here's a video showing the behavior:

http://www.youtube.com/watch?v=E6Q7oooGTLY

The other electrical issue I have is that the fuse for the gauge cluster has blown twice in the last month so this may or may not be related.

Another electrical issue is my turn signal bulbs keep blowing (3 in the last two days... it's getting expensive.)

I'm not sure if this is normal but when I was looking for a short circuit by measuring the amps when the ignition was off (although there is no draw), I noticed that when I disconnect and reconnect the battery, the tach does the "self test" (although the rest of the gauge cluster doesn't come on like it does with the ignition.) I thought this was odd and maybe related in case it's not supposed to be doing that.

As for the bulbs blowing, I don't understand why either. I've measured the voltage going to the socket and it's within normal range. It only goes up to 14V when revving the engine a lot which I'd assume would be safe for the bulb.

The bike is a 2001 Honda CBR600 F4i.

BuzZz · #2 Unread post by **BuzZz** » Fri Sep 11, 2009 7:32 am

Blowing fuses like you are doing is a sure sign that something is messed up in your electrical system. Correcting that may fix your tach problem, may not and your tach's stepper motor is shot.

My service manual for my Suzuki runs through how to check that whole system out. If your's doesn't (or you don't have one) you may have to see a dealer to figure out the problem.

#3 Unread post by **Wrider** » Fri Sep 11, 2009 8:11 am

I'm betting your regulator/rectifier is shot. Check that out and see how it's behaving.

Jave · #4 Unread post by **Jave** » Fri Sep 11, 2009 8:13 am

Wrider wrote:I'm betting your regulator/rectifier is shot. Check that out and see how it's behaving.

Someone on another forum said the same thing.

How can I test it? Can I use a multimeter to test if it's good or not? If so, what am I looking for?

#5 Unread post by **Wrider** » Fri Sep 11, 2009 1:35 pm

Yes you can. What you have to do is unplug the wire coming out of the reg/rect and turn the bike on. When the bike is running, get it to 5000 RPM, and measure the output with a multimeter in DC Volts mode. You should get about 14.5 VDC as your output. If you get more than about 15.5 or less than about 12.5 VDC then you need to replace your regulator/rectifier.
Oh, and as a precaution before you replace it, if it tests bad, check the three wires running out of the stator, and make sure the resistance is within spec when the bike is off. Not sure of the spec on that bike, but you should be able to find it easily.