Butt Puckering Death Wobbles!!!

[Hishman]

So I finally solved my charging issued on my bike after determining the replacement regulator was bad. Ever since iv'e been riding around like crazy. Over 300 miles in the past couple days.

I just have one problem my bike has a terrible wobble at anything over like 55 mph that, like the title describes, will have you quenching like crazy. it is very unstable and almost any bump in the road will send it into a gnarly wobble. Not a weave back in forth more like a quick shake of the front wheel. It nearly sent me down when it first happened at about 70mph where my bike likes to cruise. Its worse at higher speeds. I can even purposely initiate a small wobble at lower speeds by quickly tapping one side of the handle bars.

I've read somewhere that these bikes can go 86 mph "safely" and 70 isnt close to that. Has anyone had any trouble with things like this. Bike is all stock and the tires look brand new.

The only lead i have is that soft front forks can cause it. Ill be replacing the oil soon. Im eventually going for a cafe build so i want a real sporty suspension. Is 20w oil alright or can i go higher than that?

 

[Lou Ranger]

.... Has anyone had any trouble with things like this. Bike is all stock and the tires look brand new.

One of the easiest things to do is check the chronological age of the tires. Here's a thread in which xsLeo describes a wobble from old tires: http://www.xs400.com/forum/showthread.php?t=10146

Here's another "death wobble" thread which might help you: http://www.xs400.com/forum/showthread.php?t=10868

I hope yours is as easy to solve as replacing a too-old tire.

 

[Hishman]

Thanks lou. I will go threw that checklist tomorrow. My tires "look" brand new but obviously they could be old still

 

[ratrodder69]

been there not fun tires are a good place to start check pressure and age then I would check your fork bearings and wheel bearings axle tightness and wheel bearing spacers maybe not in that order

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[XSLeo]

Reading the manufacture date of the DOT number tells you how old a tire is.
There can be other reasons for a wobble. Tires is a big one, but worn swing arm bushings and or a loose swing arm bolt. Loose spokes, worn wheel bearings. Both front or rear.
Steering head bearing adjusted too loose or too tight can lead to wobble.
Low or no oil in the forks, worn rear shocks.
Quite a list. Start with the easier stuff. Swingarm bolt, When tight lift rear wheel off the ground, remove shock and chain. will the swing arm move side to side. If so you need new bushings.
On the steering head with the front wheel off the ground grasp the fork lowers and try moving them front to back. If you can they are loose. If you turn the forks left to right do they turn smooth with no feeling of notchyness. That may or not be word but as the bearings wear they get dents in the races and flat spots on the balls. These give you the notchy feel.
Tear down clean and fresh grease if still notchy replace the bearings and races. The tapered roller bearing kits are easy to install.
Loose spokes, if you can tighten them and true them your self do it, if not take them to someone who can.
Forks, drain out the old oil refill with 8 ounces of kerosene or some other good cleaner. Pump up and down, drain, repeat as needed till the kero comes out clean. Let it drain out over night to get the Kero out. Now refill with oil about 7.5 ounces. Pumpit up and down drain, this flushes out the last of the kero.
Now with the springs out forks completely compressed. Fill to 6 inches down from the top. This is easier to do than it sounds, Put in about 8 ounces of oil in each fork, pump up and down a few times to bleed out air.
Take a few feet of clear hose. Put a zip tie around the hose Snug it down 6 inches from one end. Now slip the 6 inch end down into the fork. Hold the zip tie at the top of the tube. Now you suck out the oil above 6 inches down by mouth or a vacuum tool or such.
Now assemble the forks. Repeat this every few years. It was probably never done.
Leo

 

[Hishman]

Alright well i checked all the bearings and everything was nice and tight. the handlebars fall under there own weights. I also changed the fork oil with the same rotella 15-40 i changed the oil with. Tightened up the front a nice amount. Tires both appear to be from August and November of 2012. Still have a bad wobble and the front is still very unstable. I also noticed the tighter i hold onto the handle bars the more unstable it is. I can initiate a small wobble at lower speeds and the tighter i hold on and try and stop it the longer is last or gets worse. If i initiate a wobble and very loosely hold the bars it regains itself much quicker. It actually goes away after about 2 bounces if i totally take my hands of the bars. Just something i noticed

The thing is I noticed my back tire seems really "bulgy" as i would describe it. The tire doesn't seem to fit around the rim nicely and if I turn the wheel I can visually see that the tire isnt on straight and or the rim is bent. I think i will take it in and have it remounted and the rim trued. I will also add that the back tire is tubeless if that means anything.

 

[kindest]

definitely sounds like tire related issue. I had the same issue one day and it was from the fact I had let my rear tire go nearly flat. If you have spokes on both wheels even tho the tires are tubeless you should still have tubes in there.

 

[willem]

I had a different kind of wobble/weave, more of a sideways swaying. I ended up resolving it by changing the front fork oil, but yea it could have been any of the things mentioned above

 

[Yamaguy55]

Swingarm bearings, steering head bearings and wheel bearings can all do this. Prove they are all ok one at a time. Head shake, where the bars are trying to flop from side to side, is often steering head bearings. Stock are crappy little loose balls, switch to tapered roller bearings.
Most of thes bikes have shot swingarm bushings. Stock are flanged plastic sleeves, which wear very quickly unless greased frequently. They are almost never greased. I'd guess they are shot anyway. Replace with bronze bushings from Mikes. The pivot inner sleeves are also usually shot, replace as well.

Read my post below first, but this still applies.

 

[Yamaguy55]

Alright well i checked all the bearings and everything was nice and tight. the handlebars fall under there own weights. I also changed the fork oil with the same rotella 15-40 i changed the oil with. Tightened up the front a nice amount. Tires both appear to be from August and November of 2012. Still have a bad wobble and the front is still very unstable. I also noticed the tighter i hold onto the handle bars the more unstable it is. I can initiate a small wobble at lower speeds and the tighter i hold on and try and stop it the longer is last or gets worse. If i initiate a wobble and very loosely hold the bars it regains itself much quicker. It actually goes away after about 2 bounces if i totally take my hands of the bars. Just something i noticed

The thing is I noticed my back tire seems really "bulgy" as i would describe it. The tire doesn't seem to fit around the rim nicely and if I turn the wheel I can visually see that the tire isnt on straight and or the rim is bent. I think i will take it in and have it remounted and the rim trued. I will also add that the back tire is tubeless if that means anything.

The tire isn't seated correctly on the rim. Otherwise, it wouldn't look that way. Air down, break bead loose, lube it up with something(I use WD40:it works good as a mounting lube) and them pump it up and get it seated evenly all the way around, both sides.

The other answer is the rim is truly bent, but you can tell that by spinning the wheel while it is on the center stand. I'd vote for improperly seated.

 

[Hishman]

Alright so i went ahead and took the back wheel off. I broke the bead loose and sprayed a bunch of wd40 all over it. I then filled it to 60 psi and took a hammer to the side of the tire. The bead mostly was even. How close should it be? I mean its maybe a millimeter lower in a spot or two but i can visually see the difference when spinning it. I also tried truing the rim myself. I think i got it pretty good. I also went ahead and balanced it with the weight that was already on it but it wasnt enough to get the tire to sit still. Took the bike out and the wobble seemed to have gotten better. The same speeds seem stable but i can still get it to wobble bad in the 70mph range but it still stops when i remove my hands from the bars. Its a little scary to purposely initiate a wobble at those speed so i cant test it as good as i used to.

I think i'm on the right track. I'm going to get some tools to take the tire off and get some weights and really true and balance them. I'm going to do the front wheel as well. If i can get it to be stable at 85-90 ill be happy.

Should I just hunker down and get them trued and balanced by a professional? The process just seemed so simple to me and its like 70$ a tire.

 

[phate]

@hishman

i can still get it to wobble bad in the 70mph range but it stops when I remove my hands from the bars

I had the same problem and spent a lot of time fiddling with the wheels just like you but what ended up being the fix was tightening the steering head bearing ring. I adjusted it in little increments taking the bike out after each adjustment until the wobbles were gone. It's important that you don't adjust it too much in one shot as there is a small sweet spot for the correct amount of tightening (i.e. it's very easy to be too tight or too loose)

 

[Hishman]

Awesome thanks ill do that now! How do I know its not already to tight tho? I guess ill start by loosing it and working my way up. My guess is my wobble is caused by a small number of things as the bike is 30 years old.

 

[phate]

I'm pretty sure it's not too tight because too tight is a different feeling its more of a dive left or right, then a wobble but hey its worth a trying both ways just to be sure.

Oh and while this tightening thing did work for me I did eliminate all the other sources of error first I.e. new wheels bearings, tires, swing arm bushings ect. Did all that help I don't really know as I didn't try tightening the steering head bearing first

 

[Yamaguy55]

If the steering bearings are the originals, get a set of tapered roller bearings from AllBalls and replace them. Then you'll be set for life. I'd do it even if the loose balls/races were in good shape.

As far as your question above about tire seating: it should be fully seated all the way around, on both sides. be careful with the air pressure, something could catastrophically fail if you overdo it, and something damaged or someone hurt. Those older cast wheels were often very difficult to seat tires on.

 

[Yamaguy55]

Alright so i went ahead and took the back wheel off. I broke the bead loose and sprayed a bunch of wd40 all over it. I then filled it to 60 psi and took a hammer to the side of the tire. The bead mostly was even. How close should it be? I mean its maybe a millimeter lower in a spot or two but i can visually see the difference when spinning it. I also tried truing the rim myself. I think i got it pretty good. I also went ahead and balanced it with the weight that was already on it but it wasnt enough to get the tire to sit still. Took the bike out and the wobble seemed to have gotten better. The same speeds seem stable but i can still get it to wobble bad in the 70mph range but it still stops when i remove my hands from the bars. Its a little scary to purposely initiate a wobble at those speed so i cant test it as good as i used to.

I think i'm on the right track. I'm going to get some tools to take the tire off and get some weights and really true and balance them. I'm going to do the front wheel as well. If i can get it to be stable at 85-90 ill be happy.

Should I just hunker down and get them trued and balanced by a professional? The process just seemed so simple to me and its like 70$ a tire.

Rim truing is merely patience and a good setup. I use a ball bearing equipped motorcycle wheel balancing stand plus a magnetic based dial indicator.

It takes about a half hour to do a nice job assuming the rim isn't bent/dented. If you think you can do it, give it a try. the area that has to be true is where the tire seats: you'll find the rim sides are pretty consistent, but not always. So the best time for a true is with the tire off.

If you can't find success, then take it in.

If the balance is way off, remember, the paint spot on the tire is supposed to be aligned with the valve stem. That's the starting point with no weights. It is usually very close.

 

[Lou Ranger]

This summer I was chatting with an old-time M-C mechanic who restores old bikes, mostly from the 70s and 80s. He used to be with Kawasaki Racing in the 70s.

He uses this stuff in most of his own old bikes and he recommends it to customers. In his experience it will perfectly balance tires and cause them to run cooler and last longer.
He stressed that it is NOT anything like the cheap green "slimes" that are sold for cars. Has anyone tried it?

http://www.jpcycles.com/product/353-177

 

[16VGTIDave]

If the balance is way off, remember, the paint spot on the tire is supposed to be aligned with the valve stem. That's the starting point with no weights. It is usually very close.

I'm going to suggest another way. Find the heaviest spot on the rim without the tire, but with the tube installed, and mark it on the rim. Then install the tire with the paint spot lined up with the mark on the rim. Then try balancing the wheel - If you need much more than a gram or 2, you should be looking for problems. As an alternative to using weights, use Dyna-Beads.

 

[XSLeo]

Dyna Beads work. I don't like the liquid stuff in street bikes. In dirt bikes it's ok if you ride where you get punctures often.
I tried the Dyna Beads and was very impressed. Smooth as glass. So impressed I now put them in everything I own with tires. Use the wheel weights for bullet casting.
Wheel weights just approximate good balance, Dyna beads give perfect balance.
www.innovativebalancing.com
Leo

 

[Drewcifer]

I'd say your rear is out of alignment, not uncommon. I had that issue with my bike only to eventually discover the bolts holding on my rear sprocket had one shorn half up it's length due to long ago being over tightened.

The bike simply should not wobble. It should have balanced tires, a chain that lays straight, properly aligned rear axle equally distant from the engine (you can measure this with a tape measure to the center of the rear axle from the swing arm bolt on both sides) and you should make sure your forks are properly filled and equally full.

good luck, safe riding.

Drewcifer