John Deere was on to something...In 82-84' they upgraded the ignition and clutch in the Liquifire that used the same basic motor as the Invader. The HSR ignition had a similar timing curve to the newer Polaris ignitions. So...
I recently upgraded my Invader ignition to a newer more modern aftermarket Polaris unit with excellent results. It was surprisingly easy to do. My Invader has never started or idled this well, plus it made a noticeable improvement in lower end and mid range power. I did this on my modified trail rider with shaved heads, trail ported cylinders, the OEM twin kit pipes, and Polaris P85 clutches. So I don't have any reviews how this would perform on a stock motor, but in theory it should do even better without the other modifications. I highly recommend this upgrade.
A couple things to note:
-The Polaris ignition module has the Coil and CDI in one unit.
-This utilizes the stock Invader stator.
While I don't recommend doing this to get rid of a bog you may be experiencing (they didn't come from the factory with a bog, get it tuned in correctly before making modifications), this will help make sure it doesn't happen.