Wobbles tun to tank slapper!

[R3d Ryd3r]

I know this is a common problem, but no-one seems to have it as bad as I do yet. If I roll off the throttle and release the handlebars, the speed goes from 50+ to 40 MPH the bike starts to get a head shake so bad that it would be a tank slapper if i did not grab the bars again. I have just recently gotten the bike back from the shop where they replaced the plastic on the front, so I'm sure they took the wheel off. Also, I installed the factory top case before I noticed the wobble. so I could take it back to the dealer and complain (i guess) or I could nail down the cause on my own (probably)

Does Yamaha make a steering damp for the FJR? does anyone?

If its the torque setting on the forks, what do I need to test that?

Thanks for any help

R3d

 

[otrfjr]

Take the bike back to the dealer and ask them to check the torque on the steering head nuts.

I know this is a common problem, but know one seems to have it as bad as I do yet. If I roll off the throttle and release the handlebars, the speed goes from 50+ to 40 MPH the bike starts to get a head shake so bad that it would be a tank slapper if i did not grab the bars again. I have just recently gotten the bike back from the shop where they replaced the plastic on the front, so I'm sure they took the wheel off. Also, I installed the factory top case before I noticed the wobble. so I could take it back to the dealer and complain (i guess) or I could nail down the cause on my own (probably)
Does Yamaha make a steering damp for the FJR? does anyone?

If its the torque setting on the forks, what do I need to test that?

Thanks for any help

R3d

 

[mdisher]

Put it on the center stand, jack up the front, grab the forks...

Is there any play? If so re-torque it yourself. I don't know where your located but plenty of FJR owners have the tool or you can make one.

Since they recently had this apart I'd suspect that first.

 

[quietguy]

Check the tire also... could have a bad one. Or out of balance.

 

[OrangevaleFJR]

I think knowing the kind of tire you have is important. I have grabbed my bars in decceleration (word?) when they looked like they might end up slapping. Two front tires did this for me:

Azaro and BT020's

That is, of course, if your torque is right...check that first

 

[Colin24]

I know this is a common problem, but know one seems to have it as bad as I do yet. If I roll off the throttle and release the handlebars, the speed goes from 50+ to 40 MPH the bike starts to get a head shake so bad that it would be a tank slapper if i did not grab the bars again. I have just recently gotten the bike back from the shop where they replaced the plastic on the front, so I'm sure they took the wheel off. Also, I installed the factory top case before I noticed the wobble. so I could take it back to the dealer and complain (i guess) or I could nail down the cause on my own (probably)
Does Yamaha make a steering damp for the FJR? does anyone?

If its the torque setting on the forks, what do I need to test that?

Thanks for any help

R3d

I've experiences _exactly_ what you describe on almost all the bike I have owned over the years, including the FJR.

The number 1 cause for me is tires. The design, shape and wear of the tire can cause this problem. Usually it happens as the front tire wears and it "cups". A natural occurance for the front tire. It has to do with the fact that a front tire tends to only wear under braking and the fact that the front/back (cant remember) of a tread block takes the brunt of the wear causing the tread to wear unevenly. On inspection of the tire each tread block will have a low side and a high side. It usually happens as the wear and age of a tire increases. However, I have experienced this with brand new tires. A set of Avons I ran on the FJR exhibited this very strongly when the tires were new but interestingly the "wobbling" decreased as the tire wore.

Another cause can be worn or mistorqued steering head bearings.

To check for worn bearings the usual method is to have the bike on the centerstand and lift the front wheel of the bike off the ground. Then swing the handlebars back and forth and feel for any notchiness or clicking. This indicates worn bearings. The problem with this is that it is not a foolproof method. Through personal experience I have had bikes where the steering head bearings were perfect. I had several other people who were experienced with motorcycles and they pronounced them fine as well. But when I dissassembled the front end and got the forks, handlebars and all cables removed from the tripple tree it became very obvious the bearings were shot as the tree "clicked" from position to position. The weight of the forks, wheel and drag from cables all hid the worn bearings. So the quick lift the front wheel check is usefull. But to do a proper check you need to drop the tripple tree and manually inspect the bearings.

Bearings could also be mistorqued. Note, the "nut" you see on the top of the tripple clamp does not affect bearing tightness. You need to remove the upper tripple tree and get to the two castle nuts underneath. There is a specific tool and procedure in the FJR shop manual that describes how to torque them. In years past on older bikes I had just adjusted the bearings by "feel". When I got the FJR I bought the special tool and followed the procedure and the results were far better than my old way. If your going to do this get the tool and follow the procedures in the manual. Perfect torque and handling every time.

This all said it is my guess that it is _very_ likely a worn front tire. Check pressures in the tires. Perform a quick check of the steering head bearings. If all checks out just ignore and wait untill you replace your front tire and see if its still there. I've actually come to use the appearance (and severity) of this wobble as reminder to tire wear.

- Colin

 

[burnergold2B]

I know this is a common problem, but know one seems to have it as bad as I do yet. If I roll off the throttle and release the handlebars,

What psi are you running in the front tire?

 

[ELP_JC]

First thing I'd check before anything else is that you have the wheel properly installed. Loosen the pinch bolts on the right side and bounce the suspension hard enough to straighten the forks, then torque the pinch bolts. Go for a ride, and if the wobble persists, then proceed to the other recommendations.

JC

 

[twowheelnut]

Read this. Oy, all dis woik I do for youse an I gets no respect! Vat, you tink I'm joost a Badhkin? Oy!

 

[quietguy]

Read this. Oy, all dis woik I do for youse an I gets no respect! Vat, you tink I'm joost a Badhkin? Oy!

Phew!! I'm weaving after having read all that!

 

[quicksilver]

Sounds like your front tire is shagged.

Probably has serious cupping. Pretty common on heavy performance bikes.

How many miles on your front tire. What cold pressure do you keep it at?

I had this on a front Avon. I was pretty sure I knew it was the tire.

I rode it that way until the rear tire needed help too.

New tire made the problem disappear completely.

Both Avon and Bridgestone have redesigned their front tires to help the issue.

BT-021 or Storms are the newer stuff to have less cupping.

Keep the pressure of your new tire close to 40psi to help keep the cupping away.

I also went to heavy springs in front. Can't say it helps or not.

 

[jcolman]

Taken from TWN's excellent post.

DECELERATION SHIMMYThe deceleration shimmy is a wobble many riders experience between 50 and 35 mph

when they take their hands off the bars during deceleration is unimportant and can

sometimes be tuned out by adjusting the fork for smooth operation and, if necessary,

changing the front tire.

 

[burnergold2B]

Does Yamaha make a steering damp for the FJR? does anyone?
If its the torque setting on the forks, what do I need to test that?

Thanks for any help

R3d

You can put a steering dampner on it if you want to. Try a Scotts unit. Check your tire pressure first and see if it's lower than 40psi. I just bought an '04 from Jimmy B (thanks again Jim!) and found the decel wobble. Jim had told me he wasn't sure what pressures were in the tires as it had been sitting since he bought his G'wing, sometime last year. Brand new Avon STs with less than 40 psi will produce this wobble on decel. I got home, aired tires up to 40 PSI, and voila!

It seems the front/rear balance on the FJR is more to the front, I'll wager it's around 52/48. This means that running low air in the front tire actually changes that balance even more as the front will sit a little bit lower, compounding the wobble feel as you have also removed rigidity from the tire's sidewall which is another aspect of your suspension not too many folks speak to. Whitehorse Press catalogs sells a great dial pressure gauge from AccuGage for like $20. Tire pressure monitoring is a habit I picked up in roadracing that is actually one of the cheapest maintenance/performance things we can do ourselves.

 

[quietguy]

Does Yamaha make a steering damp for the FJR? does anyone?
If its the torque setting on the forks, what do I need to test that?

Thanks for any help

R3d

Tire pressure monitoring is a habit I picked up in roadracing that is actually one of the cheapest maintenance/performance things we can do ourselves.

Of equal importance, SAFETY! Soooo many riders rarely, if ever check tire pressure. First line of defense - tires.

 

[Last Chance]

The additional weight/drag/aerodynamics of the top case could also be a factor. Explained in TWN's Doctor's thesis, I think.

I DO notice a slight deceleration "wobble" when I have it on. And I also notice some instability above 120 with the Yamaha top case on. I probably need to adjust the suspension, but I don't have time to learn how! I seldom spend any time up there so it isn't a major problem for me

LC

 

[radman]

Take it back to the dealer and ask him why you're letting go of the handlebars.

 

[twowheelnut]

:rofl:

 

[jcolman]

I'll also throw in that adding handlebar weighted ends tends to help reduce the decel wobble.

 

[R3d Ryd3r]

all good advice! thanks!

Radman, remember that I'm not really letting go of the bars, control is an illusion.

also I am going to try and reset the wheel in the forks as that is what i suspect is the problem, also it could be that the "accident" I had did in fact twist some geometry on the bike. How do I get that adjusted by gieco?

Geico--"what's the problem sir?'

Me--"my bike shimmies and head shakes on deceleration!"

Geico--"is there anything wrong with the bike?"

Me--"yes the geometry is wrong"

Geico--"I'm sorry sir but geometry is not listed as a part, you'll have to give us the part number"

Yea right, well i will report back after a change soem things around, thanks

R3d