Have a question though - My taco needle has decided to display an extra 3000 rpm so when Im idling im only doing 1000 its showing 4000 when Im doing speed the needle is right of the scale... What powers the tachometer?
Can someone shed some light on this.. please.

Let me google that for you

Im just playin around, found that, thought it was funny

If it's not running off a cable from the front wheel or take-off by the front sprocket, it's usaully a signal from the CDI unit (usually in the tail of the bike).

You don't state the year model of your ride so it's hard to say anything more definative than that.

Ern

[quote=MadHattr059;1115335]If it's not running off a cable from the front wheel or take-off by the front sprocket, it's usaully a signal from the CDI unit (usually in the tail of the bike).

You don't state the year model of your ride so it's hard to say anything more definative than that.

Ern[/quote

Here is a start...
From the wiring diagram....
If its "a signal from the CDI unit (usually in the tail of the bike)" then that's a dedicated Yellow/Green wire with what looks like a diode imbedded into the wire loom.

The non-mechanical ones see the signal to the coils. After market ones have a switch to pick the numbers of cylinders for that reason.

I could not find a speedo/tach combo for my daughter's 6-cylinder car when the speedo craped out. I installed a different one from a 4-cylinder car. The tach would then see 2 more cylinders (eclectically) at a given RPM than it would with 4-cylinders. To correct the tach reading I would divide the reading by 6 and then multiply by 4. So 4/6= 2/3, in other words I would just take 2/3 the tach reading for the true RPM.

Now back to the CBR, cylinders 1-4 fire together and 2-3 fire at the same time. This is due to emissions. Therefore the tach would only see 2 coils and the electronics would have to be adjusted so.

In your case, it would seam that you either have a short or arching plug wires or something because you are seeing double RPM's.

The first thing I would do is lift the tank and cover the bike with a tarp or heavy blanket or wait for nightfall. Start the bike and look for arching around the coils.

Edit: Phone was ringing while typing before.
I hope it's that simple. Perhaps it is the ECU as mentioned but if it were I would think the bike would run funny.

good tip tim , i think she is shorting out somewhere to, had to stop suddenly yesterday and lost power again and remained that way all the way home and tacho started doing its thing. will try the check in the dark tonite. thanks
1987 Honda CBR 1000F