paulb wrote: Gents
need some advise about my rev counter, the needle seems to be fluctuating rather than moving smoothly, i think the actual cable and counter are fine could it be the gear that goes into the top of the engine being worn
thanks
Paul
IMHO - One of two things going on here. either the tach cable is "winding up and releasing" or the tach needs to be serviced due to lubrication hardening up.
If the cable is the issue, usually you can feel the outer housing of the cable and sense a vibration in it which would tell you something's binding and releasing in the cable. You could also put the bike up on the center stand and fire up the bike. Rotate the steering head left and right and watch the tach at the same time. If the jumping gets worse, then the cable is the issue.
Another thing often overlooked is the fact that the inner cable can wear out the outer cable in a tight bend and then You'll have created burrs on possibly both the inner and outer cable. Things will eventually get worse.
Sometimes the choice of cable lubricant and outdoor temperature can be the problem. A light coat of White Lithium grease is my lube of choice. I prefer an aerosol can of white lithium grease. Remove the inner cable and spray the grease in the outer cable. shove the inner cable back in and give it a couple of turns. Pull it out and check for contamination. If there's signs of contamination, you could clean the inner and outer cable and relube it to "buy you some time" but if there's debris, it's time for a new cable.
If all that doesn't smarten up the tach, then the tach may need needs to be serviced. Before I dive into tach servicing, I would check the tach with a electric drill and a stub of an old tach cable. This would eliminate the drive from the cylinder head up to the tach as suspect. Chances are you don't have a broken inner tach cable. Not something everybody keeps in their tool box.
The likelyhood of it being the tach drive gear is slim to nill. It's bathed in oil from the camshaft area. Shy of a broken tooth on the gear, but then the teeth on the gear would just start shattering. Almost guaranteed, it's not the drive gear.
