Speed wobbles?

OK so this happened like twice to me. and i cant finger out why.

I was doing between 80 and 85mph and the bike started to like speed wobble. not really a head shake are a violant wobble but it wobbled.

I was figuring that if there was a problem with my alignment or something that the bike would pull to one direction and i would have to fight to keep it in a straight line. I cant take my hands off the bars and the bike still tracts stright.

So what is causing this wobble? It only does it between 80 and 85 mph. only pushed the bike that high a couple times.

First time it wobbled on me i was on the highway with a strong cross wind and a tractor trailer passed me at the same time a stong cross wind hit me and my bike started wobbling.

Second time was on a fairly calm day and i was going down a straight and it started wobbling on me.

Could be my seatin position? i dont really lean forward at those speeds.

 

Webels wobbly but they don't fall down. Just had to put that in there.


california had this same problem years ago when they switched to cow-a-socke don't you just love it. Any way back to the wobbly. CHP was having a wobbly problem and found it to be improper inflated tires. Just a thought this may not be your problem. CHP went back to Harley Davidson after 6 or 8 of their chips were hurt from this problem.

 

Hmm ill check my tire pressure again. Could it my wheels are not balanced? or aligned properly? But if this was the case wouldnt it wobble all the time?

 

Could just be wind shear at those speeds,racing bikes have windscreens for a reason......

 

Just happened to me (literally) On the highway at 80-85 with a strong head wind.

 

must be turbulance created by the wind

 

I used to get wobbles really bad from about 80 to 90 I just held on and throttled through it. New front tire and rotor this year hope that takes care of it.

 

The wobbles scare me lol im not gonna power through them. The roads around here aint all that smooth i think one bumb could throw the bike of course

 

OK so i finaly got around the checking my tire pressure. the tires are rated for 41psi. the front was at 37.5 psi and the rear was ay 35psi could this be wat is causing my wobbles?

 

Front tire cupped?
Try a new front tire.

 

Cupped?

 

Don't think that small of a differance could make a wobble but it is still a good idea to keep the proper psi.

 

There are alot of things that can cause this. I had them bad when I got my XJ a number of years ago.
Things to check:
-Tires. How old are they. More than 4 years? Replace them
-Tire pressure. You've already done that.
-Steering head bearings. Check for any play. If there is some, replace them.
-Wheel bearings. Check for play.
-wheel balance.
-Swing arm bushings. Check for play.

Also if you ride roads that have longitudinal grooves, these can also play havoc with you.

Hope this helps. You've gotta get it straightened out though man. Start from the easy and work up.
GB

 

check the wheel alignment if youre chain driven. i dont really think "powering through it" is a good idea, especially at those speeds...

 

How long did the bike sit on the current set of tires? Were they always properly inflated? I had the same issue from a cupped from tire. It seemed to throw the front wheel up the forks a bit and the shaking would then give me the wobbles. Feel the tire and look at if from the sides and front, make sure it's in good shape.

 

thats a little to much air in the tires, try 30 front 34 back, you want less in the front, it has way less weight on it
this sounds stupid but try folding the mirrors back, i changed the mirrors on a suzuki and got wobbles every time i got behind a truck...?
grip the bars tighter/looser maybe it's you wobbling

 

550, Those tire pressures on the side of the tire are max readings. Set the front at 34 psi and the rear at 36 psi. The date code is the engraved number. Usually the week followed by the year. 3406...34th week of 06.
Great Buffalo mentioned steering head bearings. To check them,put the bike on the center stand and lift the front wheel off the ground slightly using a floor jack. With someone steadying the bike, pull forward on the bottom of the forks to see if there is any play. If there is you need to tighten the bearings with the nuts at the top of the triple clamp. While it's up there slowly turn the bars to see if there is any dents in the steering head bearings. It will feel like the bars want to self center. If you can feel this R&R the bearings.
Another thing that can cause wobble is forks that need service or uneven damping characteristics,like one fork leaking or oil thats just worn out.
One thing you didn't mention is if you had a fairing or some other type of load on board.

 

Hold on here. From the 550 Seca book:

Up to 198lb load: 26psi front, 28psi rear.

198-423lb (max) load: 28psi front, up to 40psi rear.

High-speed riding: 28psi front, 32psi rear.

On mine, with no fairings, I run 27psi front, 32psi rear.

Try temporarily removing the fairing and see what happens; the factory brochure said it was "removable" so I removed mine and it stayed removed. Yamaha eliminated it for the '83MY Seca 550.

Both of my 550 Secas are rock-stable right up to top end. I don't think I ever got over about 70 when I still had the fairing for the '81 though, I didn't keep it long. I would try it and see.

Beyond that:

-wheel alignment (important)
-loose/damaged steering head bearings
-forks in need of rebuild
-worn out REAR shocks
-worn or mismatched tires (either end)
-worn out/damaged swing arm bushings

High-speed stability is one of the endearing traits of the 550 Seca; it shouldn't do that.

 

Wow guys thanks for all this info.

I currently to not have a front fairing on my seca i thought it looked ugly with one so i didnt take it when i got the bike. The tires are very new put on last year. date code is like something 09. My forks are weeping a lil bit.

As far as alignment goes well. my rear tire sits toward the sprocket side of the bike it is not in the center of the rear swing arm.

I need to check my bearings and everything. currently im not riding the bike becuase my chain broke. i am in need of a new chain and a set of sprockets and i put it off to long due to lack of funds. i took a link out of the chain with a chain break due to the chain being streched and not being able to tighten it anymore and went for a ride and the chain broke at the master link.

 

No problem.

The rear wheel DOES appear to be offset to the left in the swingarm, that is OK.

Once you replace the chain and sprockets, be very careful of the index marks on the swingarm and chain pullers so you get the rear wheel exactly straight.

 

I thought it may have been something wrong with the rear because of the tire being offset. ive never seen a bike like that.

I wonder if thats what was causing my wobbles the back tire not being straight. i would guess if its off even by a fraction of an inch it could cause problems.

 

could also be a bent frame. Nex time you have the bike out, wet a section of the street with water, Then drive through it and stop safely. What you are looking for is one tire mark not two If you can see two tire marks then you either have a bent frame or a mis-aligned rear wheel.

Sean

 

I sure as hell hope i dont have bent frame. the bike tracts straight as an arrow i dont have to fight it to keep it in a straight line.i can even take my hands off the handle bars and she still goes straight. i maye test your wet area thingy tommarow i cant ride it with out a chain but i can still push it it lol

 

problem could be between the seat & handlebars, that first time you had a wobble was when the semi passed you, that happens & is un-nerving, then, at speed you can run over a white line, crack, or where the heavy trucks form that ridge, because of you first experience, you automaticaly tense up on the bars, this creates a wobble.

 

Hmm good point wiz i did tence up when that semi paced me and when i get going over 70 i do tighten my grip on the bars

 

Did the drive through water test only saw one tire track so i guess thats good. wont be able to do much more till i get my chain and sprockets. The stock gearing for an 81 seca is what 14-46 or is it 15-46

 

Another thing to check, which is often ovelooked is the swingarm bushings. Not something usually looked at when the feeling is from the front end. Check for wear, if greasing helps, tightened to spec. I v'e heard a lot of guys analyze the crap out of the front end only to find it was something in the back.

 

Checked eveything in the rear its all good moves free and all that good stuff

 

OK, now go analyze the crap outta the front end! :lol: :lol:

 

Front end has already been analysed only issues up front are that my forks are weeping a wee bit

 

Did you raise your front end and move the handlebars back and forth, to check for an indentation?

 

Found the problem with mine. Put up on the work stand an spun the tire. Spotted the center line on the tire was moving and chain was binding at one spot. Pulling it off today.

 

Could that be the cause of my wobbles as well? My chain was shot and so was my sprockets and it did bind/grab the sprocket at one point

 

Because the bulk of XJ-Owners have Shaft Drive Bikes we rarely get a chance to give a tip to the Chain Drive Boys.

Back before you could get a "Shaftie" the Magazines were full of ads for Chain Cleaners, Chain Cleaning Gizmo', and Performance Chains.

Before there were O-ring Chains you learned how to Clean the Chain and apply various Miracle Aids to keep the Chain juicy and prevent wear to the Drive Sprocket.

I spotted some extra slack on the Chain of a guys Seca II. Once we got a closer look at the situation we found the the Adjusters cranked as far as they could go and both Sprockets so messed-up we drove over to the Dealer and got all new stuff to keep from eating the Chain.

 

My chain and my drive sprocket at least are shot. Im going to be replacing both sprockets and the chain.