when revs hit 10k the needle starts to float back and forth between 9k and 10k. but the bike itself still accelerates beyond 10,000 rpms. when its in neutral it works fine. it only happens when im in gear. maybe the stator, or regulator/rectifier? its an 87' with only 15k miles. suggestions would help

 

i would start with checking the electrical connections, make sure the grounds are clean.

 

I had something like that with my tach and it was the result of low battery voltage - when I'd had to jump start it. So if you don't find anything wrong with the connections, check the R/R output like you say. But it doesn't explain why it's steady in neutral, but fluctuates when it's in gear (unless a few other things are different too, like lights on when in gear etc.) Best of luck.

 

Check your connection between the regulator and the stator. I had this same issue and it had been arcing for a while (the connection had turned into black chacoal). Anyways I just ended up replacing both units with new pieces from www.regulatorrectifier.com and the problem went away. Also shockingly solved my issue of why my bike wouldn't properly charge.

 

well everything you guys are saying matches up with whats happening to me. i havent put the volt meter up to them yet but what i thought was happeing is what you guys said. i will check connections and make sure the wires didnt get chewed up from rubbing on something. after doing this all i will need is a windscreen and a new rear tire and i will have a nice road worthy cane'. its come a long way but im sure glad i did it!