Front end Flop?

[Sci85]

So I've just gotten the 90 zx-10 running and took it out for the first time today. Rides pretty decent but still have some carb tuning work to really get a sense of the power. Anyway, I noticed when turning at slower speeds, the front end had a tendency to "flop" into the turn. I really had to apply pressure to the inside bar to keep it on line. My gs550 kat is very neutral and requires zero pressure at turn in. This was somewhat disconcerting as I was not ready forint and felt like the front end would just turn in on itself if I didn't stop it.

Is this normal or perhaps something specific to this model? Do other bikes do this? I've got 3 others and none do this except this one. I don't think I like the feeling...

Thanks.

[Steve]

Whenever I put pressure on the "inside bar", it makes my bike turn even harder.

Yours is "flopping" and you make it turn even harder???

.

[Crankthat]

Cannot say I know much about the model.

Correct size rubber on the rims?
Over inflated?

[dorkburger]

Years ago I rode my brothers 87 Ninja 1000 a few times. I recall it required a good amount of pressure to initiate and hold a turn, and when pressure on the bars was released, it popped back up to a straighter line. Sounds like the opposite of what youre describing, but with the constant of a need for a lot of bar input.

[Brendan W]

I'd be inclined to apply a bit more throttle in maybe a lower gear to hold it up. The speed may be bleeding off.
Soft tyres will do this as well.

[dorkburger]

.......to add, but of no help. Thats a cool ride.

[Sci85]

@Steve - yes, at lower speed, as I lean the bike over, I need to apply pressure to the inside bar to keep the front end from turning in. Imagine a bike with the steering head bearings loose and the wheel just wanting to topple over on it's own.
If I took my hand off, it feels like it would just "fall" onto the stop. At speed, I agree that due to the countersteering effect, pressure on the inside bar would turn the bike more to the inside. In this case, this is at speeds where countersteer has no effect yet. It seems normal enough and stabile once the speeds are up. I now it's weird. That's why it took me off guard.

@Crankthat - yeah, I thought maybe the same so I checked. Front is stock size, rear is 10mm wider. Might had some effect but I doubt this much. I've found a few period tests but no mention of this odd behavior or at least in any way they have described the steering. It's really a little unnerving frankly. I'd like to figure out if this is by design or something not quite right with the front end.

Other than this anomaly, it feels fine and rides really good. Tomorrow i plan to check the steering head bearing torque. Any other thoughts or anyone else ever ride on one and notice this?

Thank guys for the input. Always appreciated.

[Crankthat]

Some symptoms probably just cannot be described well enough I think.
I would definitely give the whole front end a very thorough inspection.

The swingarm/frame bolt/shaft.
Motor mounts.
Any other fastening brace areas.
The frame itself for straightness warp-age and cracks.

Unless someone can tell you for sure 100% confidence it is ok from a description such as flop into the turn.
And then if I did not find the reason find someone who owns one to test it.

Not trying to be a wise azz on your description just think you better know for sure.

[wymple]

"I need to apply pressure to the inside bar to keep the front end from turning in."

I must be missing something. This sounds contrary to the laws of physics.

[Sci85]

@wymple - it's not contrary at low speeds. At low speeds, you have to turn the front end the direction you want to turn. This feeling is at speeds less than 30mph. If you've ever ridden a bike that's raked out, it's almost the same feeling. In a raked out front end, the tire wants to fall to one side or the other until it's up to speed. Same feeling here but I would not expect it on a sport bike. Given this bike is all stock, it must be something with the tire choice or just the way it is. Very odd though that it would be designed like this. Maybe they choose the settings to give it high speed stability at the expense of low speed handling since it was designed to go 165mph.

[Sci85]

Just to close this out, turns out it was tire pressure. Somewhere along the line I must have not checked it right. Anyway, when I did my checks this weekend, the pressure was around 20psi when it should be 36psi in the front. After setting the pressure to the correct value the front end felt a whole lot better. Still not as nimble and neutral as the old 550 suzi but much better nonetheless. It's always the obvious things isn't it?

[Steve]

"I need to apply pressure to the inside bar to keep the front end from turning in."

I must be missing something. This sounds contrary to the laws of physics.

@wymple - it's not contrary at low speeds. At low speeds, you have to turn the front end the direction you want to turn. This feeling is at speeds less than 30mph. ...

Are you available for a challenge?

Ride your bike at a steady 20 mph. That part is easy enough.

Turn the bars to the left (push on the right hand grip).

Tell me which way the bike turned.

.

[Hayabuser]

Just goes to show how important tire pressures are. It's amazing how many riders don't stay on top of this!

by the way, my TLR exhibited this exact issue when I bought it but it was the tires themselves that were the problem. They were old, hard and very squared off. The new skins made a huge difference.

in summary, give your rubber the attention it deserves!

[Crankthat]

I have rims in the shop that have 20 plus year old rubber on them.
One of the bikes they are off from I know sat outside all that time.
Pressure still up as the first day they were filled.

I have another rim that has 5 year old rubber on it.
The PO of the bike it came off from (the 3rd owner) could never keep pressure where it belongs.

As Hayabuser said keep a eye on your rubber.
And in your case I would imagine you have a very slow leak somewhere.
Likely from the valve or where the valve connects to the rim.
May just be the rubber.
Could be on the bead on, or the rim.

Likely your pressure will drop again until you get it sorted.
I would check that pressure every day until you get it sorted.
And I would replace the valve stem asap in case that is where the problem lies.


Disclaimer...
The tires mentioned above by me are all from parts bikes and I would never ride on rubber that old or hard regardless of how good they look.

[glib]

My neighbor's Harley Sportster does that. I had never ridden a Harley before a couple weeks ago and it was not a good feeling. After you have counter-steered to the left, for example, to turn right, the handlebars seem suddenly heavy and "flop" to the right. Have I described that correctly? You press on the inner side to keep the radius constant. It feels like the radius would otherwise quickly tighten and pitch you over the high side (maybe a little exaggeration). I just assumed it was a function of the rake/trail relationship and was happy to get back on my neutral GS.