I am betting some of you guys know the answer to this...

[Hypocycloid3]

Happy Holidays VMax-Bros. My '94 has developed a wicked head shake but only at 75mph. At 65 it's smooth, at 70 it's hardly noticeable but as soon as I get above 72 or so it becomes very noticeable. Smooths out again some after 85 and as much as I appreciate my Vmax's sweetspot encouragement, the impending points against my license are forcing me to figure this out. It's more of an up and down shake then a side to side that cycles in and out every 'one thousand one, one thousand two' 1 second intervals if that makes sense -so my initial thoughts were balance which I have experimented with to no avail. Even ditched rim wieghts for 3-4 oz of dyna beads in each tire but if anything it's slightly more noticeable since doing that. Tried putting a few pounds of air pressure in the forks which also made it seem worse. Fubur Fix and Progressive springs were done a long time ago and previously it was good but previous to what, I don't know since I seemed to notice this getting worse over time. Running Metzlers that are still in great shape washer moved over to make room for the wide width and all that. I have heard that an issue with the rear wheel alignment can affect the front of the bike in this way. Can anybody here verify that? ... and If so, how would I approach testing / fixing it?

All Ideas Most Welcome - Thanks in Advance!

 

[Rollie]

Have you looked at Sean morley's video regarding steering head bearings ?

https://www.youtube.com/watch?v=OW-CmACI5xQ

 

[sdt354]

I'd pull the trees and inspect the bearings & races first. Then repack & adjust if they are in perfect condition. Look for notches worn in the races. If that isn't a problem, we'll move on to wheel bearings. Before taking it apart, do the bounce test.
Steve-o

 

[MaxMidnight]

A few things to check here

 

[dannymax]

Something easy to check would be roundness/out of round using a pencil (or similar) as an indicator and spin the wheel.

 

[[email protected]]

There is no definitive answer to fix a wobble. There are quite a few probable causes.

1. Check tire condition, front and rear. Could be a bulged carcass, flat spot, low air pressure.

2. Get both wheels off the ground. Check steering bearings. Any sign of roughness is bad. Check wheel bearings front and back. Check swing arm bearings. Check wheels and or tires for runout.

Steering bearings or a tire issue seem to be the most common issues



Sent from my SM-G930V using Tapatalk

 

[Zeus36]

A new rear tire cured my wobble.

 

[Traumahawk]

I know for a fact that a wobble can be caused by bad/worn/loose swing arm bearings.

 

[dannymax]

What Hypocycloid is describing here doesn't sound to me like one of the usual wobbles....the low-speed wobble kicks in around 35 mph during decel and the hi-speed wobble isn't usually felt until well into the triple digits. This is something around 75 mph or so....I'm a thinking balance, rotating mass related, possibly belt movement type issue.

 

[Hypocycloid3]

Have you looked at Sean morley's video regarding steering head bearings ?

https://www.youtube.com/watch?v=OW-CmACI5xQ

Yep. Did this already but just did it again and issue persists. Too tight now on my ride in to work actually and gotta loosen it back up.

 

[Hypocycloid3]

What Hypocycloid is describing here doesn't sound to me like one of the usual wobbles....the low-speed wobble kicks in around 35 mph during decel and the hi-speed wobble isn't usually felt until well into the triple digits. This is something around 75 mph or so....I'm a thinking balance, rotating mass related, possibly belt movement type issue.

Exactly! I have felt that high speed - side to side "tank slapping" wobble while accelerating into long sweeping turn. Very Alarming. THIS is definitely not THAT.

 

[Hypocycloid3]

This is all up and down and no side to side

 

[davesax36]

Is there a difference in your rear shock settings? Do you have a windshield that's not on perfectly straight?

 

[Hypocycloid3]

Something easy to check would be roundness/out of round using a pencil (or similar) as an indicator and spin the wheel.

Never thought of it. Will try something like this. (assuming that you mean get a pen or something just barely under the wheel and spin to see if it touches at some point?

 

[Hypocycloid3]

I'd pull the trees and inspect the bearings & races first. Then repack & adjust if they are in perfect condition. Look for notches worn in the races. If that isn't a problem, we'll move on to wheel bearings. Before taking it apart, do the bounce test.
Steve-o

Okay thanks. Will probably have to wait until after the holiday to take apart the triple trees and inspect the bearings. By 'bounce test' your referring to what Sean describes in the video that Rollie sent above right? Or is that something specific to wheel bearings?

 

[Hypocycloid3]

Is there a difference in your rear shock settings? Do you have a windshield that's not on perfectly straight?

Interesting. I have that tallish, but not very wide midsize windshield. Wonky alignment here could really cause that? Easy to check tho' will look at shock settings too.

 

[[email protected]]

The up and down makes me think tires.
Even though you say they are good, there could be a problem.

Maybe at speed, something is happening to the carcass. Plies separating. Something that you would not be able to detect by looking at them in the garage.

I hate to throw $$'s at a problem if I don't know it will actually fix it. Based on your descriptions though, it would be something I would gamble on after checking the things already noted.

 

[sdt354]

Interesting. I have that tallish, but not very wide midsize windshield. Wonky alignment here could really cause that? Easy to check tho' will look at shock settings too.

Dave brought up an important point here. Windshields of the tall variety can turn into a sail at high speed. I have a Memphis Shades for cold weather riding. 8o mph tops when it's on. It has made my bike unstable before, beside being just ugly as hell. But up and down, motion? I think more of a weave for mine.
Steve-o

 

[dannymax]

Never thought of it. Will try something like this. (assuming that you mean get a pen or something just barely under the wheel and spin to see if it touches at some point?

Yeah, but on the top of the wheel where it's easier to watch.....maybe taped to the fork or something like that....locate it close to the wheel and spin the wheel, then do the same thing with your pencil almost touching the top of the tire.

Can you pin it down to front or rear? Do you feel it more in the seat or the bars?

 

[Rollie]

I know for a fact that a wobble can be caused by bad/worn/loose swing arm bearings.

I'm in agreement with the Hawk on swing arm bearings .