Hey folks.  Now that I seem to have solved my electrical issues, I'm going to move on to my non-working tachometer.  I need to determine if the fault lies with the gearing on the engine side of the tach cable or inside the tach itself.  Can I run the engine with the tachometer end of the cable disconnected from the tach with no issues...just to see if the cable is spinning?  Also, could I disconnect the cable at the engine end and spin that end in a drill to see if the tach moves (again, without any issues)?  Any other tips on testing and/or known common problems with these tachometers are welcome.  Thanks!

Can't come to any harm doing what you suggest but most likely a broken cable. Hope the broken bit isn't stuck in the square of the drive in the motor. Remove cable & have a look. At the tacho just find a nail that fits & twiddle it in the right direction. Doesn't take much to get it off the stop & might be stuck though lack of use if cable is broken. Drill spinning is ok but think its reverse so if you have a reversing drill then ok. Just don't damage the cable square hole in the tach.

Yes to your questions. Disconnect it at motor and kick it over.  You don't have to have it running but won't hurt if you do. Might be easier just to look in the opening and kick it over and note if the square drive rotates. You could remove the spark plug and kick it over by hand while looking at the drive down in the opening. For question two...while you have it disconnected at the motor, connect your cordless drill to the cable and run the drill in REVERSE. You can run it up to red line with a simple drill in reverse. I've taken them apart before and found a broken cable in the sheathing. Post what you find! DEET on this forum rebuilds tachs and Speedos too.

Thanks RT325 and Pedalcrazy!  I'll let you know what I find.

I had a tach cable recently that looked intact all the way down the cable but the square end, still connected was not gripping the cable. I think I just crimped it a bit and it resumed working. 

Well...I found my tach problem easy enough (at least I hope it's the only problem).  Cable was snapped just a few inches above the inlet to the engine.  I still need to test the tach itself with a piece of the broken cable & a drill.  Question:  Does anyone know of a source for replacement cables and if so, are you able to buy just the inside (metal) part of the cable if the outer sheathing is still in good shape? 

You might take what you have to an auto parts store.  There's a speedometer cable repair kit that is a new core that you cut to length and add the end. 

I vaguely remember using one from NAPA on a Yamaha but that was decades ago.

I'll have to check that out.  Thanks MarkT!

Got the tachometer working today!  Found this product at Amazon a few weeks ago and finally installed it this afternoon.  Cutting the cable to the correct length and crimping the proper end on was pretty straight forward.  Just curious if my tach is somewhat accurate; does 5000 RPM at about 55 to 60 MPH with stock gearing sound about right?  Thanks for the tip, MarkT!
www.motionpro.com/product/01-0107

Congrats!  And that speed/rpm sounds about right to me...  someone with a 250b might be able to verify.