Before I destroy another sensor

[seangee]

Had to replace my speedo sensor in October (See here). I was fortunate enough to find one on e-bay and haven't seen one since, so I'd prefer this not to be a regular thing.
Followed all the checks recommended by Chitsu and everything checked out. Haven't done too much riding since as my employer packed me off to Poland for winter. Now I'm back and rejoining the daily rat race to London.
Last few days my speedo has been behaving erratically again (i.e. no, intermittent  or low readings). This time I have a bit more info:

• It only does it when I have the throttle open, if I need to check my speed (say because I'm coming up to a camera) all I have to do is close my throttle - which has the added benefit of slowing me down 
• It doesn't always do it, but when it does closing the throttle always clears it
• It never does it at motorway speeds, problem seems to go away above about 60mph - presumably that's speed related as revs don't seen to make a difference

Anyone seen anything like it before or any suggestions on what to look for?

[Falcon 269]

Hi Sean

Welcome home.

Strange one.  Have you looked for places where the throttle cables come into contact with the wiring loom?  It could be a poor connection being disturbed by the cable flexing but reverting to normal when you close the throttle.

A bit of a reach but weirder things have happened.  I assume you've already confirmed battery voltage is good, charging circuit is providing @ 14v at 5k rpm and that all electrical connector blocks are clean and making contacts correctly.

Mike

[chitsu]

It sounds like a poor connection youve got there.
 
It may not necesarily be a wire rubbing/touching the throttle cables as the poor connection could be down to the slight movement from the engine, either way it does sound like an odd fault ?
 
I had an R1 (5JJ) a few years ago with an intermitant speedo issue, that turned out to be a fault within the actual wiring loom itself, because of this I just re-wired it to the clock block connector under the L/H fairing trim.
It maybe worth trying this as it is only 1 wire that comes from the clocks if my memory serves me ?

[seangee]

Even weirder - it goes away as soon as I change into 5th. Not ideal for commuting but fortunately on the falconised bike if its impossible to ride in fifth you aint worrying about speed cameras.


Will have a quick look at the weekend and if its not obvious will go for a new bit of wire. Chitsu, do you remember if its ok just to use a single piece all the way through?

[chitsu]

Hi,

Just checked the wiring diagram and theres 2 of the wires go directly to the clocks (WHITE & BLUE/YELLOW).
Before you go chopping wires make sure ALL the connections are good on the multiplugs, if poss check the backs of the multiplugs where the wires enter them too (you want to be looking for corrosion or broken wires).
Im fairly certain that  the WHITE wire is the one that would be causing the fault as it is this wire that gives the speedo its necessary signal. One piece of wire should be ok, but dont forget you also need to wire it to the C.D.I too.
If you do go down the route of chopping the wires, make sure you cut them far on enough from the plugs so that you COULD rejoin them if it is not this that is at fault.
One thing I would be tempted to do first is disconnect the plugs from the clocks, speed sensor & C.D.I unit and test the wire for continuity from one end to the other and also check that the loom does not have a short to earth by twisting & pulling at the loom from the speed sensor  end back to the clock plug.

[seangee]

So - just had it all apart. No sign of corrosion, damaged wires or water ingress. Wires both showed continuity all the way through and no leaks to earth (not that surprising because the speedo works a lot of the time). Put it all back together and its still there, so fiddling with it didn't accidentally cure a dodgy contact. No mechanical interference either - sorry Mike you had me hopeful for a while.


Should I snip and replace the wire(s), or just run a piggy back? Chitsu, I assume you mean run a wire from the multiplug under the infill and then split it taking one end to the CDI and the other to the sensor.

[seangee]

BUGGER BUGGER BUGGER.


Just been out with my shiny new white cable and its still there. New white cable is actually blue. I snipped North of the plug under the left infill, South of the plug under the right side cover and just above the CDI. (Realised my previous question was silly as a piggy back wouldn't fix a leak to earth).


So that leaves the connection into the clocks and into the CDI since I've taken the rest out of play. Always assuming that the white cable is the fault. Both look clean and sound.
So

• Any suggestions on where to go next?
• Anyone know why it needs to go into the CDI - doesn't seem to make any difference to performance when the sensor is disconnected

I'm still puzzled by the fact that the speedo only ever stops working under acceleration and only in the first four gears. No mechanical interference anywhere so I'm wondering about electronic ...

[seangee]

Update but still no progress:

• [size=78%]Replaced both wires.[/size]
• [size=78%]Removed clocks and visual [/size]inspection[size=78%] of PCB - no signs of dirt, corrosion, cracks or water[/size]
• [size=78%]Removed and refitted sensor[/size]

Additional info: The odo still ticks over when the speedo is reading zero.