Kawasaki Sportsbike Riders Club - Australia - Online Forum

Hi Guys, Hope you can help me with a bit of a problem with a head shake on the ZX12 that develops when rolloing off the power. It starts at about 85k and keeps going down to about 40k. I ahve checked Bearings, Tyres, Wheel Bearings, Clamp hight on forks, Suspension etc.

According to the mechanic he says that is to do with the angle of the front forks and "harmonics" and this could be changed by lowering the hight of the rear of the bike or maybe changing the head clamps to some other kind (if so what?) to change the trail angle. this will change the overall handling in corners as it wont tip in as quick apparently.

According to the kwaka website this is a common problem, if so what have you done about it?

Councillor

Councillor wrote:Hi Guys, Hope you can help me with a bit of a problem with a head shake on the ZX12 that develops when rolloing off the power. It starts at about 85k and keeps going down to about 40k. I ahve checked Bearings, Tyres, Wheel Bearings, Clamp hight on forks, Suspension etc.

According to the mechanic he says that is to do with the angle of the front forks and "harmonics" and this could be changed by lowering the hight of the rear of the bike or maybe changing the head clamps to some other kind (if so what?) to change the trail angle. this will change the overall handling in corners as it wont tip in as quick apparently.

According to the kwaka website this is a common problem, if so what have you done about it?

Councillor

Common? not from what I know on stock standard, but your mechanic may have got it right with what he said, do you know if the forks have been raised in the tripple clamps or lowered (should be 5mm or less sticking out the top clamp bracket from memory std), and do you know if washers have been put on the rear shock upper mounting bolt?

If any of this was done then you would expect a bit of a wobble as the guys that have done it will tell you. Maybe a steering damper may help but it wont solve why.

HTH

All that is indicitive of your symptoms, what about excess front tyre wear?

You could always stay above 200kmph or and keep the front raised in the air...

as Jonno sez..not a common issue on standard ZX12rs
(unless there is a cause like faulty head stem bearings, worn tyres etc)

tyre pressure can affect the 12s handling...dont let the front go under 36psi on the road
but headshake on an otherwise mechanically ok bike is generally due to an attempt
to sharpen the handling by raising the rear and/or dropping the triple clamp down the forks.

I would set everything back to factory standard...then see if there is a problem.
(just bear in the mind that factory settings are for a 5' 0" 65kg japanese rider with glasses )
small increases/decreases in preload can be made to match your heavier/lighter weight
after first...checking SAG

hth


Smitty

never had an issue mate, no idea.

reckon it's tyres, bearings, steering head nut or something like that..they are a very stable bike.

have you raised the rear ?

Stringline the wheels too to make sure they are in line!

Strika wrote:Stringline the wheels too to make sure they are in line!

yeah check it, especially if it's just come back from service, they never line rear axle up right

As said above or had some bitumen surfing at some stage

I had exactly the same problem on my old TL 1000 S, all it turned out to be was the front wheel had thrown the weight off & it was way out of balance.
Quick check - if the front wheel has a weight on it, mark its position & then remove it & go for a spin & note if it's better or worse, if it's better, leave the weight off & get the wheel balanced if it's worse, just get the wheel balanced.

Just buy a 10, their front ends are much more stable

Mick C wrote:Just buy a 10, their front ends are much more stable

Gotta have something to make up for the weedy midrange

As that motivational poster says.....an awesome ass makes up for a lack of rack

Phil wrote:

Mick C wrote:Just buy a 10, their front ends are much more stable

Gotta have something to make up for the weedy midrange

As that motivational poster says.....an awesome ass makes up for a lack of rack

awesome thread derail !!


Councillor - some good advice above - my 12 has never suffered the same problem you have described...could be a wheel weight has dropped off, or even am out-of-round tyre ? That happens, not often, but it can happen.

Its almost *guaranteed* not to be the triple clamps or anything like that, these bikes are very stable at all speeds up to the State limit.....

Gosling1 wrote:...

Its almost *guaranteed* not to be the triple clamps or anything like that, these bikes are very stable at all speeds up to the State limit.....

listen to Gos

Thanks Guys

Have checked all the things you mentioned apart from a new set of tyres as they are both reasonably new so they will be replaced in time...

Other than that the bike is a dream ride with more power than an insane lunartic ever has a right to have at his disposal...

thats why they are fun

*yawns* yeah I know

Hey Mate

Question for you - has the bike done some fairly serious back wheel travelling with some not too gentle landings?

Mine had a very similar problem but more like 110-60kph, investigation finally led to head stem bearings flogged, but along the investigation path we found a number of issues which I believe pointed to some serious monoing (broken engine mounts, cracked radiator mounting, fatigued front fairing bracket, hairline cracks all over front fairing, etc). Oh and first hand knowledge of some harsh landings by yours truly.....

Anyway, if the answer may be yes, I'd get the head stem checked asap.

Cheers