Front End Wobble or Shimmy

I have an 81 750 Seca that I recently purchased with about 20k miles on it. I have noticed that at speeds above about 5 - 10 mph I start to get a wobble or shimmy in the front end. The wobble is bad enough that you would not be able to ride with anything less than 2 hands firmly gripping the bar. I am currently away from my bike and am unable to check anything, but I wanted to get it "fixed" as soon as I am home with it so I am trying to compile a good "list" of items to check and or repair. The tires are both in good shape and seem to be balanced well. The front forks do leak a little bit of oil, it passed our state inspection so it's not a bad leak.
A friend of mine told me the frame is likely bent, which would mean a major fix to get rid of it.
I am currently in the process of doing some restoration to the rest fo the bike, but if there is a possibiliy of a bent or damaged frame, I want to know that before I put anymore money into it.
Thanks
8)

 

All you have to do is LOOK for damage. A frame that's bent or damaged LOOKS like it.

My money is on Front Wheel Bearings, something loose or not right up front ... or, The Number One Cause for a Wobbly Front End.

Driving While Intoxicated!

No. You'd never do that!

Test and Adjust or replace without even bothering to check ... those Old, Probably Pitted and Worn-out Headset Bearings!!!

 

Would an alignment problem cause this?

 

Possibly, but Rick is spot on for the most likely and least expensive culprits. I'd start hunting there. New fork seals and head bearings would be where I would start (the former because they leak, the latter because they are never looked after, I'll guarantee it).
I'm curious, how can you can tell that the balance is ok on your rims? Have you had them checked?
Additionally what have you seen that would suggest that you have an alignment problem?
I guess this list of questions will do for the moment. Let's hear back from you when you get a chance to look over the machine with a critical eye.

 

The tires can still be bad and cause a wobble even if they "look" good and are balanced and they go bad after 4 years so if there's any doubt replace them.
The rear shocks too but I would check the wheel bearings and head bearings like already mentioned. If the frame is out of alignment or forks bent you could probably see it because the wheels would not line up.

 

Trust me when I agree with these guys. I too just went throug the same problem. Everything "looked" good from the start but didn't end that way. A lot of little problems can lead to just one (seemingly) problem. Do yourself some big favors that will pay off in the long run: Replace your head bearings with tappered barings; replace your wheel bearing and if your tires are more than a couple of years old, change them. My front and rear tire looked great until it got up to about 65 mph then the bike would would shake and shutter in the FRONTEND, not the back. So I changed the front tire, the worse of the two but still had the same problem. I went through a month of hell till I finally got it straighened out buy making all these changes and each one of these changes made some improvement but the biggist was the "great" tire on the rear.
It hurts the wallet if you have someone else do the work but get your hands dirty and take pride in knowing it was you that made this bike an awsome ride.
Good luck
the Buff

 

To answer the question, No, I'd never drive intoxicated, lol.

As far as the balancing, you are right, I don't know the tires are balanced or not I just know there are no missing weights, so I'll have to keep that in mind.

I jut recently purchased this bike and have only put a couple hundred miles on it. The guy I bought it from, is a friend, and had the bike for 13 yrs. Although not a bike mechanic, he is an auto/aircraft mechanic. He has taken very good care of the bike and when i asked him about the wobble he said he never noticed it. I think that may be tied to either because it sat for 6 months to a yr before I bought it or he chalked the wobble up to poor road conditions.

I will ask him about the wheel bearings, when the last time it was that he changed them. Also I am already planning on getting a new set of tires.

Besides all the great info I'll get for possible solutions, my other main reason for the post is to comfortably rule out the possibility of a bent frame or front end before I sunk "too" much money into everything else.

Are the front bearing something that I could tackle myself or should I just let the shop do it when they put my new tires on? What is a decent/average price to pay to have them replaced?

What are the Head Bearings? Were are they? What do they do?

I have to admit, I may be a fairly capable shade tree mechanic when it comes to cars, but in 18 yrs of riding I have never been much of a bike mechanic.

 

My bet is it's the steering head bearings. Put the bike on the centerstand and jack up the front of the bike with a jack under the frame rail or the engine. You want to get the front wheel in the air where you can rotate the handlebars left and right. What you are looking for is to see of the bearings are self centering. If they are then your steering head bearings are trash and you need to replace them with the tapered roller bearings. What usually happens is that the steering bearings dimple the races a tiny amount. Its actually hard to see or feel. I just replaced mine and now I can ride the bike without my hands on the handlebars.

Sean

 

Out here in the heat what happens is the grease dries out and hardens and the bearings and races rust so the bars get hard to turn. Either way it's bad.
If they are in poor shape be sure and replace them with the new tapered roller bearings, they look just like car wheel bearings but cost a lot more, about $35 usually.

 

Start with easy and cheap; check your tire pressure. Under-inflated tires could give you a wobble. It's probably something more serious, as mentioned above, but you never know.

 

The fact that the bike did a good deal of sitting would light a big neon arrow pointing at the headset bearings. Since it a bit of work and involves taking down the front end ... you might as well get all you ducks in a row and do the hole front. Wheel bearings, fork seals and headset bearings.

The good news is that the bearings for the wheel and headset are a Universal size used in many, many applications. The tapered rollers you'll get from a bearing supplier are rated much higher in load and turning ... same holds true for the front wheel bearings.

The bearings from suppliers are rated for much higher load and rpm's than the stock ones.

You'll be very happy to have new bearings in there and have a "Day One" newness happening ... rather than riding around on bearings that have sat and developed a hitch in them.

 

Another possiblility if the bike sat for an extended time, flat spots on the tires. These will cause a mad vibration at speed.

 

ok, thanks for all that. I will move ahead with the front end rebuild then. So, how do I find the right bearings if I don't order them from a bike shop?
I went on bike bandit, great site for OEM parts btw, and found "All Balls" for $40, but no wheel bearings. Old Bike Barn had Wheel bearings for $14.

I will update after I am abel to get back to my bike and do the fixes.

Thansk to all

 

Forget the balls for 40-Bucks. They're standard 1/4-Inch Balls. 40-Bucks worth of those at a Bearing Supply Store should be a few hundred ... easy!

 

When I did my front end I got the tapered bearings from the Old bike Barn.
I had never done this job before but I've turned a wrench or two over the years. The word on the street was that you should spend a good day on this job. I had it all tore apart and back together in 2 hours. The whole job took closer to 4 hours because I had a heck of a time putting the front wheel back on. I felt like a complete moron as I contemplated heaving the wheel over my 6 foot fence into the street on the other side. Talk about DUH! It's much easier to remove the brake caliper then put the wheel on then replace the caliper. Don't look like an idiot like did.
Good Luck its not really that bad of a task.
The Buff

 

Actually if it's all balls racing then its tapered bearings from china. Had I known I would have bought a set of bearings that were made someplace else beside's china. Probably has something to do with me being a machinist and seeing chinese made crap that was supposed to be made to a certain standard but wasnt............ Hmm anyone want some lead in there paint????......... Next time I will demand that the bearings be made either in Japan, or the USA or someplace that actually stands by the standards that are demanded. Right now I am wondering if the AllBalls racing steering head bearings that I purchased from Dennis Kirk is going to last me more than a few years or should I just go to the local bearing shop and demand quality bearings. OK sorry rant off for the walmart mentality for parts. When was the last time that we bought something from there that lasted more than a few years but we have some old antique that was made before we were born that is doing the job that was asked from it. OK I am ranting wayy to much.... Want more proof?? check out the latest chinese bike... All of our XJ's will outlast that crap.
OK Chinese rant off I promise............... wait have you heard about the..................

Great Buffalo, the job should only take at the most three hours to do. It helps if you have all of the tools or can use stuff laying around the shop that will work to tap out the races and tap in the new ones. BTW hopefully you do not freeze too much this winter... I used to live in Mobridge SD as a kid ............. I know what F'in cold is


Sean

 

A cheap trick for getting the wheel back on without removing the caliper is:

Drive a small hardwood wedge between the brake pads and open the bleed nipple. Drive the wedge in separating the pads. Close the bleed nipple.

Not you can remove the wedge and have room to slip the brake disc between the opened pads without removing the caliper and wiggling it on.

The wood won't hurt or score the pads. It just opens them enough to allow you to position the brake rotor between the pads without the energy consuming fight and the marring you can do to the pads with a pry bar, screwdriver or anything else you might try before heaving the wheel over the neighbors fence!

 

If your races are in good shape, Rick is right. If the balls are worn, chances are that the races have taken a beating as well. Inspect them carefully. Any blemishes and you should get the new bearing set.

 

just an update. I replaced the wheel bearings the other day with an All Balls front bearing kit. It seems to have helped with the wobble some. I think I have narrowed it down to the fron tire though. I noticed my pressure was low, like 26 psi. So I aired the tire back up to the 41 recommended on the tire. The wobble diminished. It didn't go away thought. So it looks like I am/was chasing a problem with 2 causes. After I replaced the bearings I was able to go "no hands" until around 30 mph. Then the wobble came back. After some close inspections on the front tire I notice cracking inbetween the treads. So, off to get a new tire. Since the back is showing a lot of wear I am going to get a new set. I am trying to decide between the Metzeler Lasertecs and the Battlax B-45's. They are about the same price the only thing I noticed is the B-45's don't come in a 110/90-19 for the front all they offer is a 100/90-19.
I don' think it will make much of a difference. Anyone have any opinions on those tire choices?
I will update again when I can get the wife to allow the $300 purchase for the new tires. :mrgreen:

 

Do you have a 110/90-19 on there now? If you do that could cause the
wobble just from having a tire that's too big.