Bar Shake and Valve Stem Question

[Dredgshadow]

Today I went riding, thankfully the weather has been better. I noticed that around 50mph I was getting some shake from the handlebars, especially under deceleration. I have read everywhere that the Ninja will shake a little when engine braking, but I feel like this might have been a little more. I was going to start by checking tire pressure and if that didn't fix it I would have to take it in to check balance.
Well, my dang valve stem is stuck and I'm working on getting it off but I can't check pressure until I do. Could the tire pressure be causing this? Regardless I need to get that darn cap off. Any suggestions for accomplishing this.
Thanks

[rojoracing53]

Want your feeling is normal "for this bike" and unless your down to 15psi a doubt tire pressure will help. The severity of the shake has gone up and down with my bike over the last 35,000 miles. there has been two things that make it much better but never completely gone.

1. a new front tire
2. new or possibly properly adjusted steering head bearings. I just opted to replace mine because after 35k I figured the crappy ball bearings had probably started to wear a grove in the races and they had so it was time.

things that will make your bike shake more

1. this

[Motofool]

Originally Posted by Dredgshadow

Today I went riding, thankfully the weather has been better. I noticed that around 50mph I was getting some shake from the handlebars, especially under deceleration................Regardless I need to get that darn cap off. Any suggestions for accomplishing this.
Thanks

If I understand, you can not remove the plastic cap from the tire valve.
If so, wrap the valve with some leather and use two pliers, one to twist the cap counterclockwise and the second to prevent the valve from rotating.

There are things that make any wobble stronger:
- Loose head bearings.
- Worn swingarm bearings.
- Removed end bar weights.
- Big tail box.
- Loose chain.
- One or both tires dynamically unbalanced.
- Low rear suspension / high front suspension.
- Worn wheel bearings.

[Dredgshadow]

First of all, Rojoracing, that picture is hilarious. Also, I see what you are saying about the pressure having to be severely low.
Motofool, I think my chain is loose by about a half an inch. I plan on fixing that tomorrow but I don't know if that is the cause of my problem or not. We will see. It's also possible that the road was bumpier than it looked. It looked fine but maybe the bumps weren't visible. My valve stem btw is actually a blue metal the the previous owner put on I would assume. I check pressure regularly but maybe the cold "glued" it on. I hit it with some WD40 to maybe loosen the threads. My fears is messing up the actual tire part of the stem if I go too hard on the cap.
Since it's only happening at almost exactly 50mph on that road I'm thinking either tire balance, or that road. It's the only place on my way home I got that fast so tough to say.

[Dredgshadow]

Also sorry to double post like a noob, but it seems important to say that the shaking isn't violent. But being my first bike, within what limits is normal?

[Motofool]

Originally Posted by Dredgshadow

.......
Motofool, I think my chain is loose by about a half an inch.............My valve stem btw is actually a blue metal..........I hit it with some WD40 to maybe loosen the threads. My fears is messing up the actual tire part of the stem if I go too hard on the cap.
Since it's only happening at almost exactly 50mph on that road I'm thinking either tire balance, or that road........

When decelerating, the chain slack moves to the upper portion and induces some whipping, which may induce some lateral movement in a swingarm with worn bearings.
If you pull the clutch and the wobble stops, it is the chain-bearings.

WD-40 will damage any surrounding rubber.
It is an aluminum cap over a brass thread: some heat from a heat gun or hair drier and two pliers with protecting leather if needed will do the trick.

The speed of 50 mph creates a resonating frequency for your steering:
http://en.wikipedia.org/wiki/Resonance

Originally Posted by Dredgshadow

.........it seems important to say that the shaking isn't violent. But being my first bike, within what limits is normal?

About 5 degrees in each direction / 2~3 cycles per second is normal.

[rojoracing53]

Originally Posted by Motofool

If I understand, you can not remove the plastic cap from the tire valve.
If so, wrap the valve with some leather and use two pliers, one to twist the cap counterclockwise and the second to prevent the valve from rotating.

There are things that make any wobble stronger:
- Loose head bearings.
- Worn swingarm bearings.
- Removed end bar weights.
- Big tail box.
- Loose chain.
- One or both tires dynamically unbalanced.
- Low rear suspension / high front suspension.
- Worn wheel bearings.

before yesterday I had 6 out of 8 of those things going on with my bike and yeah my shake was seriously bad even without the Mtb. Now it almost gone but I haven't checked my swingarm yet and my rear shock still need to be replaced to match my stiffer front end. I can't fix the givi top box because well that **** is just to damn convenient to not have on there all the time.

To the OP if its shaking with both hands on the bars under deceleration then I'd bet loose of worn steering head bearings. Careful if you ever try to take both hands off the bars because they'll start shaking slow and go to insane tank slappers before you know it.

[Dredgshadow]

Okay, well I'm not sure to what degree they are shaking as far as a measurement.
I learned that riding loose really helps a lot so I'd say at the worse I can feel them bouncing between my palm and fingers within my loose grip. I wouldn't say they are really pushing to go past that point with any intensity.
I have taken my hands off the bars and the bounce some but they haven't gone nuts on me. Being a revvy twin like the 250 I expect some shaking when my hands are off the bars hence quick deceleration due to no throttle. Thanks for the input guys, I know that the internet doesn't give the best possible picture of what is normal as far as wobble.

[Motofool]

Originally Posted by Dredgshadow

........Thanks for the input guys, I know that the internet doesn't give the best possible picture of what is normal as far as wobble.

Please see these threads to watch a real tank-slapper and to learn more about this annoying phenomena:

http://www.ninjette.org/forums/showt...t=tank+slapper

http://www.ninjette.org/forums/showt...ht=tankslapper

[Dredgshadow]

Originally Posted by Motofool

Please see these threads to watch a real tank-slapper and to learn more about this annoying phenomena:

http://www.ninjette.org/forums/showt...t=tank+slapper

http://www.ninjette.org/forums/showt...ht=tankslapper

Seen a couple of those and a few more on Youtube. If it weren't for those kind of videos I probably wouldn't have the paranoia that I do!

[Motofool]

Originally Posted by Dredgshadow

Seen a couple of those and a few more on Youtube. If it weren't for those kind of videos I probably wouldn't have the paranoia that I do!

Any improvement?

I have found this additional cause:
http://www.knowmotorcycles.com/view/...alignment.html

[Dredgshadow]

Originally Posted by Motofool

Any improvement?

I have found this additional cause:
http://www.knowmotorcycles.com/view/...alignment.html

I got new tires and with them got the bike balanced. Seems to have completely fixed the issues I was having. Thanks for the check up bud.

[Motofool]

Originally Posted by Dredgshadow

I got new tires and with them got the bike balanced. Seems to have completely fixed the issues I was having. Thanks for the check up bud.