Mini Tankslappers around 35-55mph

[cbrsmurf]

So these are the symptoms

When I let go of the clip-ons and cruise without both hands on the clip-ons while the bike is still in gear, the handles begin to shake around 50mph and they get bigger and bigger to about 1 inch tankslappers each way. When the speed decreases to about 25mph, it goes away. This happens almost all the time, no matter what condition the road is in.

I have not tried to reproduce this while coasting in neutral.

So I figure this has something to do with the front suspension. What could it be?

1) Loose head bearings?
2) Loose front axle/wheel?
3) Unbalanced front wheel?
4) Different height forks?
5) Different volume of fork oil in each tube?
6) Lower and upper tripple bolts over or under torqued?
7) Preload?

Only mods to front suspension:
Changed fork oil and oil seals about 3 months ago and put in some 0.8 Ohlins fork springs. Dropped front 25mm, but recently raised it back up so it's only dropped 13mm. Don't know if the tankslapper problem was happening before or not.

I'm pretty sure the head bearing is tight and when I measured the fork oil, I used a graduated cylinder to put in the exact amount. Fork height is the same.

[kc1717]

well start by returning it to stock geomerty and see if the problem remains. that would be the the best thing to start with without riding it myself

[GetnJgyWitit]

Your front forks still might be to high in the triples or lower your rear a little. Also what tires are you running. Some are more twitchy then others.

[Philo]

My CB750 would do that and my stearing head bearings are trash. Above 65 or so it would start to oscillate (sp?) and if you let go of the bars it would get worse and worse until you grab the bars or crash.

Haven't changed them and ridden it yet, though, so, yeah, maybe that's it???