Tachometer gone wonky

[PaulG]

Rode to work last night.  When I started my 92 ABS the idle "settled down" at 3,000 rpm.  I knew this was'nt the actual rpm by the sound of the engine, which sounded like a normal 1200 rpm.  When I started riding I noticed it was basically reading double what it should.  On the expressway at 110 km/h it would normally be just under 4500 rpm, but was displaying about 9000 rpm.  Ambient temp. was about 20 degC

I have an 18 tooth front sprocket, so the rpm will be a little lower than stock, and my clutch is not slipping (brand new in April).  I checked my Clymer manual but they have nothing other than how to disassemble the dash.  I looked at the wiring diagram and it shows a green wire running to the digital ignitor and tee-ing off to an ignition coil.

When I left from work this morning I stopped for gas.  When I switched on the ignition and let the ABS cycle, I heard some clickity-crackling coming from under the dash.  I can't remember if I've heard that before.  I believe the ignitior unit is secured to the inside of the fairing? When back on the freeway the rpm issue was still occurring, but seemed to be about 1.5 times what it should have been, though it kinda bounced around a bit.  Ambient temp. was about 10 degC

I've never encountered this before on any bike.  Mind you this is only the second one I've owned that has an electronic tach.

Any ideas on how to troubleshoot?  Hopefully it's just a loose connection at the least. My electrical know-how is somewhat wanting, so if you have any suggestions use the FJ's For Dummies approach.

Oh yes - last week on a midweek ride with a buddy, the bike started to run rough at low rpm when coming to a stop, and would'nt idle, then stall.  This started happening about 1/2 way through our ride.  At speed it was fine.  It eventually seemed to clear itself up, and I put it down to bad gas or pizza.  Maybe this is related? Or coinkidink?

I had the bike running two days ago and everything seemed fine.  I don't want to ride it until I can figure this out.

thanks

[movenon]

I don't know a lot about the tach but I can tell you a few things I do know about access.

To remove the cluster:
Remove the seat and fuel tank
Remove the left and right fairing dash panels
Remove your windscreen
Looking at the cluster trim molding from the rear or rider position there are 2 phillip head screws (actually JIS screws) left and right side, easy to spot.  Remove them.
On the front of the fairing under where the windscreen was mounted there a 2 more phillip head screws. Remove them
Now you can carefully pry out the cluster moulding.
Looking at the cluster on the right and left side there are 2, 10mm nuts. remove them.
Unhook the speedometer cable from the front wheel.
Now you can pull out the cluster, unhook the electrical connectors as you remove it.


The ignitor/CDI is mounted under the fairing on the right side of the frame. If you need to unplug the wiring you will probably have to remove the right scoop. Easy to do.

Out of memory that's how you do it  

George

[Scooterbob]

Sounds like a bad ground, possibly at the coils or ignitor.  Did it by chance get wet when it was acting irrationally?

[PaulG]

Sounds like a bad ground, possibly at the coils or ignitor.  Did it by chance get wet when it was acting irrationally?

With the warmish days and cool nights of early fall we are getting a heavy dew setting in right after dark.  My bike is covered (usually) outside, but during the day (when I'm sleeping - work nights) I take the cover off if theres no rain in the forecast.

I'll try the inspection route that movenon described above - the Clymer appears to be similar - and check the connections to the ignitor and the coils.  I'll apply some dielectric grease on the connections and see what happens.

Thanks