I'm no expert on TS185s but as far as I know the tachometer is driven from the oil pump via a helical gear shaft. My guess is you can get to it without splitting the cases. Take the oil pump cover off and have a look. If it's the shaft it's still available from CMSNL.
There are a few others here who know the bike but in the event they don't see this post you could do worse than joining the VJMC group on Facebook. TS185's are popular so there's bound to be someone there who will know exactly what your problem is. I spent 6 months trying to find a wiring diagram for my '69 Yamaha online and someone sent me one in an hour on Facebook.
|