Fu@#ing death wobble

[TeXB12s]

I work at a MC shop..typically jap bikes and very rare see any buells dropping in. I made a super move and bought my first Buell and threw away over 10yrs of experience riding and wrenching jap bikes. So im basically a squid again. When i get a customer that rides in complaining about front end wobble, its always tough to diagnose when nothing is visibly wrong. So the first time i took my 04xb12 on the highway and noticed a horrific wobble, almost a SWAY like the way a shark swims, i knew it was going to be a bitch. Neck bearings, f and r wheel bearings, fork rebuild 3 different front tires, and it still untrustworthy at high speeds. I did convert my stock bars to a renthal setup and replace clamps...but it wobbled before this conversion. So big question to my ranting..if i have done everything to the front end..what could cause the wobble??? Rearend maybe?

 

[user_deleted]

Sir: see PM i sent you. revise your personal info for your own well-being.

a high-speed WEAVE is always rear-end related.
a high-speed WOBBLE is always front-end related.
read the below article. though H-D specific it is the finest i've ever come across. often over-looked on rubber mounted driveline type bikes(all XB's) are the engine fasteners/mounts/rubber donuts. your solution will be found in this article.

https://ridermagazine.com/2009/11/1...wobbles-how-to-avoid-them-and-deal-with-them/

 

[Chicknstripn]

Come on Lunatic! You know people don’t like to read these days!
I thought the article was spot on.
The things I would check, on my Buell if it was having stability issues:

1) tires are they the EXACT factory size and a known good brand for a Buell? I mention this because I’m a cheap a$$ and put Shinko ravens on my bike ONCE. Had issues with wobbling anytime I went over 90mph.

2) Bearings. Are the steering head bearing, wheel bearings(front and rear) in good order?

3) Axels and spacers. Are the wheel axels in good serviceable shape? If they are slightly bent or have a gouge from a bearing seizing this could cause stability issues. Same goes for the spacers.

4) Engine mounts and related links. Check the front and the rear main engine mounts. Any issue with either of these and the bike is bound to have stability issues.

5) Swing arm pivot bolt. If it’s loose or worn your entire rear end will have stability issues.

6) Suspension(this should have been mentioned after tires). Is your suspension in good working order? All clamps and mounts good and tight? Do the rear or front seals leak any fluid? Have you set up the suspension for your weight and riding style?

I’m sure there are other things I could mention or have missed but the truth is, it doesn’t matter what bike or type of bike you’ve worked on for your life time. The basic geometry and mechanics are the same across all the major brands. It’s time to systematically trouble shoot.

Make your own list and check items off only once you’ve physically inspected them.

Good luck

 

[BuellyBagger]

Wow, great article John. I nearly had to decide to "bail off" one time on ye ole Ulysses. Good thing I was wearing my brown pants. Couldn't blame the bike for that one, she was tight... the dumbass on top of it was the issue

 

[njloco]

I had a bad high speed wobble in the front on my Triumph when it was new ! Ended up being the tires, which were also new. Changed out the tires and have had no problems since. I'm not saying it's your tires, especially since you already tried different tires on the bike. Since you initially took the front end apart due to the problem, I would rule out that it was installed wrong. Did you check the rim for run out or possibly being bent ?

 

[TeXB12s]

Chiknstripin Ya both neck bearings and wheel bearings replaced..but that #4. You said "bound" to have problems. Is that just theoretical or its been known to cause issues? Ive asked this question before thinking it could be the issue and was told it wouldnt be related. I should just replace them anyways just for up-keep. I just dont want false hope thinking it will fix my issue lol.

 

[Chicknstripn]

Download a service manual from www.buellmods.com
There should be a procedure in the service manual for checking serviceability of said parts.
Please check parts before you replace them otherwise this issue could get REALLY expensive.
Also check swing arm pivot bolt.

And Njloco had a good suggestion with checking that your rims are true.

Think about the way the swing arm is attached to the bike. It is literally bolted to the back of the lower engine case. If ANY of the structure that is suppose to hold the engine in place is loose, you’re going to have a handling issue.

 

[wickedchop]

Sounds like a good area to steal a Buell and grab some Chinese........

 

[cossack84]

Mine did that too, after replacing all the same parts I raised front forks by 1 mm. Bike ran a lot better, then I raised it 0.5mm more and it completely stopped.

 

[njloco]

So cossack, are you saying that someone lowered the front forks for some reason or it came from the factory like that ^^^^^^^^^^ ?

 

[Cooter]

1.5mm of (effectively sag) made any difference!?! Ummm.... It would be like having the bike steer differently whether you ate dinner or not. Glad that worked for you, I wonder what the cause was?

 

[mmcn49]

In 72 I bought a new R75/5 Beemer. That bike and the model in general had wobble issues. Problem was caused by one or the other fork binding. One or the other would bind up while the other slid. A couple redesigned parts solved the issue.

 

[Silverrider]

I had a wobble once here was the issue.

 

[cossack84]

So cossack, are you saying that someone lowered the front forks for some reason or it came from the factory like that ^^^^^^^^^^ ?

I bought the bike that way, they were ran up into the triple tree all the way in against the clips.

 

[cossack84]

1.5mm of (effectively sag) made any difference!?! Ummm.... It would be like having the bike steer differently whether you ate dinner or not. Glad that worked for you, I wonder what the cause was?

I'm not familiar enough with motorcycle geometry to be able to explain it, but it is not as simple as you put it. Adjusting high of the front end has effect on entire set up. After repairing/replacing all the usual suspects, then, setting rear sag, front sag, adjusting compression and rebound and finally raising the front of the bike up, it is rock solid at any speed. Where is before it was ok up to 90mph, after that, she was very wobbly and shaky.

 

[Owenator]

Mine did that too, after replacing all the same parts I raised front forks by 1 mm. Bike ran a lot better, then I raised it 0.5mm more and it completely stopped.

Sorry to sound dumb, you made it so there was more or less fork sticking out the top yolk?

Thanks

 

[cossack84]

Sorry to sound dumb, you made it so there was more or less fork sticking out the top yolk?

Thanks

More, I moved forks in 1mm increments.

Edit.
I was wrong, less fork sticking out the top.

 

[34nineteen]

More, I moved forks in 1mm increments.

"Usually" raising the bike (lowering the tubes) tends to lead to high speed unstability. Usually...

Can you now see the stopper rings (#19) on the tubes? Maybe a PO pulled the rings off the tubes and lowered the front too much? Usually with those in place, the front end can only go down so far... but with the clamps loosened you can slip over them with enough pressure.

 

[Cooter]

One MM of compression = about 6.2lbs* of weight with stock spring rate at stock sag. So pretty much nothing. The change in rake/trail is four digits past the decimal point. I call BS.

I appreciate a discussion on steering geometry and the theory is correct:up:, but it's only theory in such an infinitesimal quantity. If you start talking in single digit denominator fractions of an inch (because Murica') then... maybe.

Theres NO way a mortal human could tell the difference by raising the forks ONE MM, or that it would affect the handling of a motorcycle in any way.


*rough but close calculation, but really... one mm!? sheesh. Crank up the heater! Its 72* now and I'm more comfortable at 72.0001* hahahaha.:angel:

 

[Cooter]

"Usually" raising the bike (lowering the tubes) tends to lead to high speed unstability. Usually...

Yup. Exactly. Because it's increasing the rake* and Buells are already pretty maxed out!