Pretty in Pink, dunno why
Join Date: Feb 2009
Location: Redondo Beach
Please be careful working this problem - tank slappers are unnerving and dangerous. But then, you already know that...
Can you try moving a few pounds forward with a tank bag? Have you tried leaning over the tank (which should move quite a bit of weight forward) at the onset of the slapper?
I don't think that raising the forks is going to materially affect the rake of the bike or change the wheel base. Fork rake and trail won't change.
Are you running fairly high pressure in the front tire? If so, reducing pressure may help. If you have the forks set up stiffer with those springs you may be getting a bounce that initiates the slapper.
Did this start with the suspension changes or with the installation of the tire?