It seems from the fast guys that the general rule is to accelerate. Chopping the gas can actually make the slapper worse.
Odd, when I was in that position on my old 929 it REALLY wanted to shake it's head. I was doing it in order to get the front wheel up, though.FWIW - a very long time ago when the world was young, I borrowed a friend's BMW R75/7. It was shod with Dunlop TT100s which, at the time, was recognised as a complete no-no. The only tyres which had stiff enough carcases to damp out the oscillations of the old airhead's flexible frame were Continentals and Metzlers. It was well known that the Dunlops were prone to instability and possible tank slappers.
This didn't seem to bother my buddy - partly because he was a big guy and his mass damped out any oscillations before they developed into anything bigger. However, at the time I was probably 140 lbs, dripping wet and on the way home one evening on his bike, I hit a dip in the road at c. 80 mph and the Beemer immediately began to shake its head quite violently. I remembered reading that one way to stop this was by standing up on the pegs and leaning forward over the steering head so I very quickly assumed the position; almost peering at the headlamp glass. The bike stopped shaking its head, I sat down and carried on my merry way.
As ever - YMMV.
OK there are two kinds of tank slappers. One is a quick 3 oscillation swing that happens when the front end is light and you are under power. These self damp by the 3rd swing but it is caused by the front wheel being partially unloaded and the power twisting the front end/chassis. The other kind is more scary, that would be the click to click full-on slapper. Front tire chirping with each lock to lock movement. These are the bad ones.
In both cases if you lower the power the front wheel will take a better set and lessen the gyrations but it may or may not be recoverable. The general rule for the little ones is that if it doesn't feel like it's getting worse, then keep the gas on and ride through it, bikes wobble, no big deal. The real, click to click, tank slappers are much more serious, your hands might be stripped from the bars before you can get the bike settled but you want to reduce power and gently try to get control. The bike will decide if you win this contest or not. My rule is that by the 4th click, you are usually in trouble, look for a soft place to land.
So which kind was this?
I've got a pretty decent steering damper on my bike, so I'm not all that concerned about tankslappers.
It appears that a lot of people think a little bit of headshake is a tankslapper. If the bars aren't going full lock, it's just headshake and you can usually ride it out easily enough.
I rarely get much headshake. I've got pretty aggressive geometry - the front of my bike is lower than stock, and yet the bike leans WAY over on the kickstand - but it's pretty stable. Sure, it'll wag the front end a little if I'm hard on the gas out of a turn over bumps, but that's about it. For some reason, this SV both turns quicker and is more stable than my old 929.Yeah, OK. My Mach III had both a friction damper and a piston damper when it when stop to stop on me, granted that was early seventies but a damper is a band-aid to a serious problem.