The tach on my '12 Sportsman 500 HO is squirrelly. I briefly searched the forums and found only one member with a similar problem (
http://www.polarisatvforums.com/foru...44684-rpm.html), but the audience has been left in suspense for a few years now.
Before I get too far into this, keep in mind this is a tach issue, not an actual engine RPM issue. The engine appears to be running perfectly. Unfortunately, I have no idea when this problem began as I usually have the display set to the trip meter.
Anyway, the tach at idle reads 1,000-1,200 RPM. With headlights and brake lights OFF, advancing the throttle causes RPM reading on tach to drop to 500-600. Now, holding the throttle steady, I can turn on the low beams and get the RPM reading to increase drastically. Put on high beams and RPM reading comes up a little more. Squeeze the brake and it comes up still more. And get this... operate the winch (in or out) and the RPM reading increases just a little more. Bear in mind this is all at a constant engine speed.
In addition to the winch, mods on the machine include the three headlight mod and wiring inside the Tamarack lounger to support the third brake light (LED). However, I can replicate the RPM reading problem with the headlight mod disabled (relay removed) and the lounger disconnected.
There's one other issue I do NOT believe is related, but I mention it here JUST IN CASE I'M WRONG. There's an occasional hiccup when starting. Every so often the display will go blank and the starter will disengage as if the whole bike is losing power. This has happened with the original battery and with the new replacement. It doesn't happen often, but it's really obvious when it does. There's never an issue on successive attempts to start. Again, I'm not looking to resolve that issue here. I know it likely requires its own string. I brought it up here in case someone out there is aware of a correlation between the two problems.
I suspect this is a bad ground issue, but I can't find it. I'm hoping someone out there overcame a similar issue. Suggestions I don't need to hear are to ignore the problem, leave the display on something other than RPM, leave the headlights on, etc. I prefer everything to work. Any ideas?