Headshake problem

I have a headshake problem on my Suzuki SV650S. I don't know if it the
correct term but here's the problem:

When I ride at over 50 mph and I hit a sharp edge bump, my handlebar turn
violently to one side at first and then the front end stabilize itseft after
a few oscillation. On very bumpy road (lots of succesive bumps) I can feel
that the front end become unstable. If I lossen the grip, the oscillation
become more evident. Like if the front end jump from side to side...

Help please!

 

Ahhh ... tank slappers ... lovely aren't they? Could be a multitude of
possible problems. Cheap ones to check are tyre pressures, steering head
bearings, shock settings etc. Has the bike always been like this, or has it
just occured, or have you just bought it? A good suspension set up
(possible change of springs and valves) will sort out most problems,
otherwise you can always go down the route of a steering damper but you
shouldn't really need one on a SV650S (I wouldn't think)..

Cam
'03 CBR954RR

 

In addition to this good advice, check the BACK end of the bike very
carefully. Look for:

- Bad bearings in the wheel or swingarm.
- Check the tire to see if it is worn flat in the middle of the tread.
- Incorrect tire pressure.

It seems weird, but very often problems in the rear of a motorcycle
can cause instability in the front end, and vice versa.

HTH, JS.

 

I ride an SV650s too...it has had bent fork tubes and triple clamps and
still has not had a head shake problem...thats rare on an SV650...something
is very very wrong.

Especially at just 50 mph...bad things are about to happen if you keep
riding that thing...take it to a shop, get it checked out.

 

Tire pressure and tread profile can be a source of oscillation/head shake.
You might want to investigate that first, then consider steering head
bearings, or other fork related stuff.

 

Negative... the front of a motorcycle wobbles (high frequency)... the
back of a motorcycle weaves (low frequency)...

If you want to address the wobbles... concentrate on the front not the
back of your motorcycle...

Larry L
94 RC45 #2
Have a wheelie NICE day...
Lean & Mean it... the extended warranty in every corner of your life...
If it wasn't for us the fast lane would rust...
V4'S are music to the seat of my pants...
1952 De Havilland Chipmunk...
Yank and bank your brains loose...
http://members.ebay.com/aboutme/-xlax-/

 

I'd also suggest:
* Front wheel balance[1];
* Rear wheel substantially out of alignment[2];
* Underinflated front tyre;
* Fork oil due for replacement[3].


BTH
[1] You might have lost a balance weight.
[2] Check the index marks on the swingarm.
[3] If the level gets low things can get *insert Agent Smith style
pause[4]*... interesting.
[4] Apologies to whoever it was I just stole that joke from.

 

What bloody problem, ya whoose? Headshakes are great fun, they remind
you that you're alive(for at least the amount of time it will take to
hit the ground anyway) and make you feel like you're a GP star
but seriously, check the basics. Once upon a time(ie, 2 months ago) I
got new tyres and voila! headshakes while fully cranked through turn 2
at Eastern creek I figure it was front tyre pressure too low, up the
pressure 2-3PSI and now she only shakes when upright and
accelerating
Mark
ZXR400

 

In recent years I recall my former SV doing the "head shake" thing
after an unexpected power wheelie while turning. The front came down
out of line and I got an oscillation to correct the alignment. Also,
an R6 and my Sprint at the track while accelerating hard over rough
pavement but very mild, compared to that one on the SV.


I suggest that you lighten your weight on the bars. A death grip can
magnify oscillations up front. Other than that, odd tire combinations
on those old late 70's bikes would cause straight line, near tank
slappers, at high speeds. Scary shit but I doubt many modern bikes
suffer frame flex.



Bob Nixon
Phoenix AZ
01 Sprint ST "RED"
03 Suzuki ST "SILVER"

 

Cam, did you trade-in your ZX6 on that Blade or did you find a buyer?

 

I don't *think* this is necessarily correct. Something wrong at the back
end frequently translates to front instability.

Always start at the back.....

 

A bad back translates through the whole mass of engine... rider and
frame at a lower frequency... thus you feel a weave...

A bad front translates through the soul mass of forks and wheels
pivoting on bearings at a higher frequency... thus you feel a wobble...

Larry L
94 RC45 #2
Have a wheelie NICE day...
Lean & Mean it... the extended warranty in every corner of your life...
If it wasn't for us the fast lane would rust...
V4'S are music to the seat of my pants...
1952 De Havilland Chipmunk...
Yank and bank your brains loose...
http://members.ebay.com/aboutme/-xlax-/

 

I certainly wouldn't rule out the swing arm bearings.

It makes sense to put the bike on its centerstand and check
both front and rear for excessive play in the wheel bearings
and forks.

 

Only if you know it's all straight. If you're careful, you can use
a long straightedge and a helper to check the alignment properly.

 

Neat.

 

washisname that used to post here, a salty old fart that testifies in court
on these issues claims loose swing arm bearings can induce the front end
into a speed wobble as well....Id say thats probable if the front end had
its own problems as well, and maybe in the in the case of a crotch rocket
with a steep fork angle,

Phil Scott

 

I dont think anyone disagrees with that...its just that we are saying bad
bearings in the back can get the front end wobbling on its own where it
would not otherwise...compounding effects sort of thing...sort of like
getting drunk with two red heads.

Phil Scott

 

That's true, but you have to admit that the index marks are usually a
good place to start. ;-)


BTH

 

But many riders can't tell the difference between a wobble and a weave
until it is explained to them.

So, it was fair advice.

 

I think you will find that Larry was judging the problem on the description given.
And, as any mechanic can tell you, that's a risky pastime.

To give Larry his due, the symptoms do sound like a wobble and not a weave, but the
only way to be really sure is to ride it oneself.

So, personally, I'd start checking for problems at the front and THEN go onto the
back if need be.