Not too long ago, prior to learning about the kegler clamps, I actually asked the members here if someone in the forum who lived nearby would take my bike for a test ride because I had checked everything and my bike still handled poorly. I was out of ideas since I inspected everything I could think of and had replaced my swingarm bushings which didn't help.
The discription of my handling in that thread was that the bike felt like it "snaked" down the road. On that thread, someone clued me into the flaw of the early model's swingarms of which I was unaware. Installing the kegler modification completely changed my bike's handling from "scarey" to "precise". The handling flaw was remedied by the kegler modification, and the result made "cause and effect" sense to me.
In my bike's case, the whole bike felt "rubbery", meaning it felt like it wiggled around and drifted around in the general direction where I pointed it. It did not inspire the desire to go faster... It makes sense that it was a worn swingarm tube because the sloppy interface matched the handling flaw.
SO,... If the bike feels rubbery and drifts around where you point it, I would think some worn out part is expressing it's "play" in the way the handling feels.
But,... If the bike feels rigid and doesn't wiggle around alot, but like it wants to go left as you say, I would suspect some critical misalignment (which is what you are persuing)
What to make of the combination of "pulling left" and "tank slapper" feel at speed,.. I would think a twisted headstock, which you are checking...
