Welcome to another Maine rider. I just bought my '83 500 a few weeks ago, and have the exact same problem.
Mine has a brand new battery in it.
Mine had many other issues that could be causing the issue - old gas, original spark plugs, a shop cloth for an air filter, so it's hard to say exactly what the problem is, but someone on the tech page had some suggestions for me today - you'll see my post close to the top.
There are a bunch of .pdf manuals available for download for free on the discussion page.
What year is your bike?
Mine has a brand new battery in it.
Mine had many other issues that could be causing the issue - old gas, original spark plugs, a shop cloth for an air filter, so it's hard to say exactly what the problem is, but someone on the tech page had some suggestions for me today - you'll see my post close to the top.
There are a bunch of .pdf manuals available for download for free on the discussion page.
What year is your bike?