Motorcycle Repair: Potential Ground Issues - No Spark, harley sporster, loose ground

Question
1995 1200 Harley Sporster: For sometime I've been trying to get a Dakota Digital speedo to work.  It stopped registering the speed after only 800 miles. I've rewired it several times and replaced the speed sensor. I've started numerous times in this whole process. On the last rewire I started it, drove it .. no success it still said speed err.  I parked it as we were moving.  I went to start it to put it in a trailer and there was no spark but it would turn over. I soon noticed that if I held the sparkplug wire near the end it would spark through the plug (basically its using me as a ground - I'd get a bite). If I didn't hold it near the end it wouldn't spark. I assume this means there is a ground issue. I also believe this may be the issue with the speed sensor.  Can a loose ground cause loss of spark.  Where are the key grounds located on a 1995 1200 Harley Sporster

Answer
Hi Darrell,Sounds like a nightmare to me !The two main grounds are the battery negative strap, and at the rear engine mount.If you are getting bit at the plug wire near the coil I would think you have a break in the wire and should replace them or they are not seated properly.