31K Kidney Clocks - Tacho Intermittent

[element137]

Hi all 

I have the clocks apart three times now trying to solve an intermittent problem with the tacho ( either works , or it don't )

So far :
- Clocks/mechs cleaned, re- assembled with new ( hard type ) faces.
- Tacho spins up OK on a drill
-Speedo works all good 

Changed the aftermarket tacho cable to Yamaha OEM ( I thought the inner cable on the aftermarket one might be a bit short so was dropping out a touch )

Problem still persists - every time I have had the clocks apart and put them back - first time tacho will function properly - leave stand for a few days - wont work ?

I have read on here that they can get gummed up /sticky without use - so I am thinking maybe another more in depth clean - I just wanted to rule out whether this can be a symptom of either the clock mechanism is just worn ( I do have a spare if I need to swap it out ) OR can it be a problem the crankcase end ? 

[crogthomas]

I had the same issue on my LC2 for a while. The solution was to put a tiny drop of 3in1 oil with a tooth pick onto the little bronze bearing that carries the tacho needle. If you've cleaned it, it will be dry and grabby, which is a technical term I've just made up.

[shaunthe2nd]

If you have cleaned the internal tacho mechanism, including the internal bell which can get caked up with sticky fluid from the needle damper, and cleaned the needle and needle end stop, it should eliminate that, although these are common faults, but easily cured with a clean.
I also assume the cable entry to the rear of the mechanism is clean, often caked with old grease, add a drop of 3-in 1 oil or similar to make sure it spins freely.

When you removed the tacho, was the alloy cable entry section loose? Sometimes it breaks away from the rest of the housing, and you can feel movement in it. if so, the mechanism needs replacing.

If these all ok, and you using new OEM cable, then it could be wear in the cable entry at either engine or clock end.
You could run the bike with the cable disconnected to the clock, but fitted to engine, just tape it up so you can see if the cable is actually spinning when revving the bike. If its not spinning then its a problem with the engine end.

I've never done it before, but you could connect the tacho cable to your speedo and go for a ride to see if needle is moving on the speedo, it won't be very accurate, but give you an idea. Off the top of my head, 5000 RPM would show as around 30mph on a speedo dial, I think!
Don't do it the other way round though as speedo spins up much faster than the tacho and you could damage the tacho.

Let us know how you get on.
Shaun.

[midlifecrisisrd]

I'll put money on it being the needle stop

They are made of rubber and go tacky so the needle sticks to it when left sitting

Your welcome 🤣

Steve

[element137]

Thanks all for the input - I will have another go this weekend with the suggestions above - its so frustrating as I have literally nothing left now to do on the bike and typically , the very last three or four small jobs to complete have been a nightmare ! - just waiting for bodywork back from paint - cheers for the advice -

[element137]

And Steve wins -
Took the tacho cable out and started the bike - tacho cable is rotating consistent -
Took the clocks apart again - run up on a drill, needle stuck then broke loose off the rubber stop - so gently cleaned off the edge of the needle, and the rubber stop with a tiny amount of BDX on a cotton bud - seems less adhesion between the needle edge and rubber stop now - fitted clocks back to the bike - all OK - time will tell if it sticks again- but if it does - at least I know what to fix now - many thanks for the help and advice-