Tank Slappers

[humdinger]

I've had many bikes over the past 48 years & a few 1400's. I've had my current 08 FE since 2010. Since I had it, it has the tendency to start a tank slapper at speeds above 25-30 upwards if I take both hands off the bars. I've used different make tyres, different pressures, one up, two up, luggage, no luggage. std settings on the shocks front & back but nothing seems to help. Bikes got around 14k on it now so still low mileage & everything is in mint condition. Any suggestions?

[seth]

Stearing head bearings being slightly to lose ?
Mine starts to wobble when it's slowing down to below 30mph when my rear tyre is getting towards the end of its life.

[Daytona]

I've had this issue on a couple of bikes over the years and it's been the front tyre.both times I've had this the tyre looks ok but on replacement it's been cured,

[KiwiCol]

I'd plump for front tyre wear, however, head bearings being a tad loose won't help either.  Just another thought, do you have any sort of fairing on? Sml or lge? 

I've had a nasty experience of tank slapping on the 14, just came on at (cough cough) 180K!  Thought I was going to bin it, lucky there wasn't any other traffic on the road (I mean riders on that part of the track) It stayed slapping all the way back down to 120, a hell of a ride I can tell ya. 

[Kiwifruit]

One of the scariest things in my life. On my XJ 750 in the 80's in Aus. Few of us out on a ride, im in front, we catch up to a GTHO Falcon. Pull out to pass and the Falcon drops a gear. Anyway not a lot in it when l hit a pothole......Tankslapper big time.
Im veering across the wrong side of the road but know this will all stop when l get to the gravel on the shoulder.......which it did but at about 150 kmh.
Long story shorter, l did manage to come to a stop without crashing.
The lads behind were as white as l was. The Falcon had gone.....time for a soother and a nappy change.
Tyre was a Pirelli Phantom. Great tyre that just wanted to grip !!

Funny how vivid some things stick in your mind.

[seth]

Also worth checking tyre pressures.

[KiwiCol]

I had an XJ750 as well Col!  Used to trip between Tauranga & Orewa regularly. Was a while ago now though

[Hooli]

Sticky steering bearings do that too as well as loose bearings, tyre wear etc that others have mentioned.

[Latty66]

The first 14 i had was a k5 and to cut a long story short it was the swing arm it had been manufactured 7mm ont one leg lower than the other after changing every bearing  rebuileding the forks changing the shocks tires everything
I got talking to a guy who built some stuff for hickman took the arm up to there place he jigged it and bingo he reckoned no damage just a manufacturing f**kup with that bike you could ride to 104 mph no worries everytime you went over that tank slapper so my addvise would be get that checked 

[Batkwaka]

Way back when the GSX1100EFE suffered this problem and was apparently due to incorrect tension on the steering head bearings. It may be worth checking.

[Latty66]

Yeah i tried everything rear to front aliglment was perfect changed swing arm bearings ,wheel bearings , head stock bearings ,tryes ,shockers rebuilt forks i even looked into getting the frame jigged .
It allways had a very light weave at low speed  going up and down which you could hold striaght  but like you say let go of the bars and it would slightly wobble. riding between sort of 30 and 90 it was quite steady the reason for the weave/wobble is the gyroscopic effect the rear wheel has on the front trye as it try's to right its self the 7mm differance on mine would be 3.5mm top right and 3.5mm bottom left so you could not visually notice and rear to front was in line i.ll try and add a pic of that bike . But apart from low and very high speed the bike rode and handled well but once pushed past 104 the gyro effect kicked in big style the replacment arm i bought sorted this out completey i had that checked before i fitted and the tolerance was 1.5mm your fault could be the same or somthing else you seem to have checked the obvious like me you may have a friday arm

[Latty66]

Another pic