MT09 (FJ) Tracer Steering Wobbling

[pattonme]

I hereby recind the aero-theory and apologize for the tangent. I can't find it now but I was using a Google image of an FJ cockpit that had blanking plates contoured around the fork legs as the premise. I'll shut up and stick to suspension.

[skipperT]

The reason I chimed in in the first place was that it one shouldn't mask handling and chassis dynamics problems with a steering stabilizer.

 
 
.... That I agree with. Steering dampers are nice but they do numb out how the bike is MEANT to obsorb road imperfections, abrupt direction changes, etc. IMHO.
 
-Skip

[clint]

I eagerly await your experience riding a luggage equipped FJ09 at 140mph with accompanying video footage of the fork action. With or without a stabilizer.

I've had my FJ-09 with OEM hard luggage up to 135 mph several times (ECU Flashed) with absolutely no wobble...period. There is a back road that is WIDE open about 40 miles from home where I can do this safely. This bike is rock solid.  
Just got back from a weekend near Deals Gap, staying at Iron Horse MC Lodge. The FJ-09 was nothing short of perfect on the Cherohala Skyway, Deals Gap, 180, etc. It was comfortable, powerful, compliant, smooth and just thrilling!
 


 

[Guest branthopolis]

The reason I chimed in in the first place was that it one shouldn't mask handling and chassis dynamics problems with a steering stabilizer.

Totally agree with this...
 

[thruster8999]

the issue with lift isn't that the fairing is "flying" or acting as a foil. I don't have access to a 120+mph wind tunnel but there isn't "huge amount of daylight" between the forks and the bodywork - Yamaha put blanking panels in there to keep the cockpit area calm but the side-effect is it traps air. It is my contention that the lift is coming from what amounts to a 'ball' of high-pressure air trapped in the nose to radiator section. Look at the FZ1, the FZ8, the versys 1000, sv1000. Only the FJ has such large vertical distance between fender and fairing nose.

Sorry to keep banging on about this but what you've stated in my opinion simply isn't correct. If you look at the bike from side-on the radiator is angled downwards and backwards. This means any air striking the front of the bike is mostly directed downwards towards the downpipes and engine. 
Any air channelled upwards can easily escape in the space around the steering head and up through the cockpit area.  Below is a picture looking down through the handlebars. As you can see there is plenty of space to allow air to be funnelled up through the gap. In fact on full lock I can get my arm through that gap.  The second image shows how it looks with the bars straight.  I simply can't understand where air would get trapped, sufficient to lift the front end/extend the forks.  The more likely cause of the forks extending in the video you referred to is that the rider's weight shifted backwards as speed increased. Likely combined with them pulling on the bars in the process of holding on as the speed increased thereby causing the forks to extend somewhat.
 

 

 

 
Air can get trapped if it cant escape fast enough. I think the air is hitting the rad and moving upwards but the opening are to large which cause the air to move up and out of the openings but not big enough for all air to escape and flow smoothly. It cause turblance.
Having smaller openings would let the air travel down and around the sides.
Hope that makes sence. I really dont think yamaha put the Fj in a wind tunnel.

[scuff]

Don't forget that the angled screen and had guards will cancel it out any perceived air bubble by pushing down :-D
I use a steering damper to keep the bike from going completely out of control, not to hide a problem that I am aware exists.
Most people won't ride it to the extremes that may cause the weaving, it's when you take it by the scruff of the neck and wring the nuts off of it, cranked over and braking with the rear wheel lifting off of the ground on our bumpy and broken up British back roads.
I am happy to ride it within its envelope, it is still good fun and a very capable machine. Just be aware that it has limits which could surprise you one day when you are really trying. :-)
 

[captainscarlet]

Air can get trapped if it cant escape fast enough. I think the air is hitting the rad and moving upwards but the opening are to large which cause the air to move up and out of the openings but not big enough for all air to escape and flow smoothly. It cause turblance. Having smaller openings would let the air travel down and around the sides. Hope that makes sence. I really dont think yamaha put the Fj in a wind tunnel.

 
But the radiator is angled downwards and backwards which means that most of the air hitting it will be forced down towards the exhaust downpipes and bottom of the engine.
 
CS

[scuff]

Most of the air hitting the rad thankfully passes through it to stop our engines overheating. As the rad is angled forward, the air will hit the fins and if anything will cause downforce.
To be honest, all of this talk of aerodynamics may make a difference on a formula 1 car or an aircraft, but I don't think it makes any difference to bikes with their slab like aerodynamics.
Anyway, we could get really technical and put our anoraks on and say that as the wheels move through the air, due to their rotation the air will cause a low pressure area below the wheel and a high pressure above it, thus the Magnus effect will force the wheel down.
That's it, bored now.
 

[pattonme]

> Most of the air hitting the rad thankfully passes through it to stop our engines overheating
 
Not to step into it a second time but no, the radiator is only capable of passing about 25mph worth of air. Over that speed it might as well be a piece of wood. Pressure does build against the radiator and any flat'ish portions of front cross section. Since the forks are angled, this force will necessarily result in an upward component. I do not wish to speculate how much of that is countered by a downward component generated by the windscreen or fairing components to include the winglets on the bars.

[scuff]

Ah but were you figures obtained at sea level, or at higher altitude.
 
Perhaps those riders who enjoy ragging their bikes around the Himalayas would care to compare with me if the pressure build up at higher altitudes causes less weaving problems than those of us at lower altitudes.
 
My pressure tests were done at a local wind tunnel, and I found in fact that due to the shape of the ducting around the tracers rad, it actually passed 43.742789% of the air through.
 
Right I'm off to blast around on my bike and find some sports bike riders to embarrass, when we stop to chat, I will bore the feck off of them explaining aerodynamics, and how it allows me to ride around them on corners because of it. (rofl)

[captainscarlet]

Right I'm off to blast around on my bike and find some sports bike riders to embarrass, when we stop to chat, I will bore the feck off of them explaining aerodynamics, and how it allows me to ride around them on corners because of it.

 
Haha, brilliant. More riding and less bollocks is just the ticket....
 
CS

[air]

I have now Increased the preload and So far so good..
I also removed the handguards.
 

[pattonme]

An official Givi response:

the most recent Monokey information booklet that has a maximum recommended speed limitation of 120km/75mph (see page 4).
 
GIVI is an advocate of safe riding, although our European pamphlet has the above maximum recommendation, which is probably more relative to their own highway speed limitations, our US customers would be advised to not exceed the posted speed of any public road and or highway.

[grayhawkglen]

Hello folks,
I have been checking in on this topic via the forum for months now. I too experience the wobble at speed. I have been SO impressed with my FJ-09 since I purchased it in March, and this would be my only REAL complaint (that fuel gauge is BS though).
I have been the suspension adjustment route (stiffening) and it made my ride better. Better for me because I have been on some great Euro sport bikes over the past years. This did not cure my wobbles though. I still like to get after it at times, so this is a real bummer.
Can anyone recommend a dampener for the FJ?
Thanks and sorry if this has been asked elsewhere in the forum.

[ULEWZ]

Hello folks, I have been checking in on this topic via the forum for months now. I too experience the wobble at speed. I have been SO impressed with my FJ-09 since I purchased it in March, and this would be my only REAL complaint (that fuel gauge is BS though).
I have been the suspension adjustment route (stiffening) and it made my ride better. Better for me because I have been on some great Euro sport bikes over the past years. This did not cure my wobbles though. I still like to get after it at times, so this is a real bummer.
Can anyone recommend a dampener for the FJ?
Thanks and sorry if this has been asked elsewhere in the forum.

This should find all the damper threads: Add this to your command line:
steering damper site:fj-09.org
 
 
Most are using the GPR steering damper (myself included). Other FZ riders, have kluged together some cheap far east fork dampers for cheap, but you have to fabricate the brackets and it works marginal at best.