81 GS650L Tach Jumpy, Low?

[DaveP]

I have finally finished my electrical mods with the coil relay and replacement of the R/R unit and took the bike out for a test ride. It was running really well and my initial ride around the neighborhood turned into a 40 mile ride...

The only thing that was off a bit was the tachometer reading. It was fine at idle and lower speeds as well as all of the times in the shed that I was checking electrical readings at 5,000 RPM. I had replaced the cable early in my rebuild process since the original cable had the end snapped off. The tach cable connects to the valve cover and I used an OEM head gasket.

On the road with acceleration the tach needle was initially very jumpy, 1,000 RPM jumps, up into the 7-8,000 rpm range while the engine was accelerating smoothly. Less jumpy as time went on, but then never really increased outside of the 5,000 range. I was winding it out pretty well, so not sure why the readings aren't keeping up.

Any ideas on where I should look to improve the tach readings?

Thanks,
Dave

[JTGS850GL]

It sounds like the internal mechanism in the tack assembly is sticking. You can try to spray some lubricant into the opening where the tach cable attaches but in many cases you need to open up the tach housing and get to the rotating assembly directly.