Fixing the speed wobble on an '85

[Hatter]

I have an '07 I have put 10k miles on, no wobble up to 135 (by speedo) yet.unk:

 

[dannymax]

Getting a handle on this wobble thing is like trying to grab a handful of smoke. The fix for one bike has no effect on another.
My '85 had both high & low speed wobbles. That was 'back in the day' and nobody knew anything about steering head bearings and there weren't any cool forums like this to learn from.
So I lived with it-luckily!
I really don't think there is a "one fix for all" with this issue, there is prolly something in the initial v max design that makes it very sensitive to tolerance variances in many areas of the bike, and the fix is gonna be a trial & try thing. IMO anyway.

 

[jfeagins]

Try putting the bike on center stand, start it, put it in about 2nd gear and let it idle along with the rear wheel up. Go back and with plenty of light to see, watch the 'run out' of your rear wheel/new tire combo. I'll bet you'll be amazed at how much that new tire DOESN'T align side to side. It'd only take the smallest fraction of an inch of run out to create a very nasty tendency to tank slap at the front after applying length vs weight physics. I guess if you could test the front similarly, you might have a problem there, but much harder to test.

I think the reason the tank slapping intensifies during braking or slowing is because when you first start applying slowing force and the front end becomes heavier, it also starts adhering that much better to the roadway, causing any minute wobbling to come clear up the forks and into the handlebars, instead of being somewhat absorbed by roadway slippage. ???

Proper head bearing and wheel bearing adjustment and condition is a MUST, but I still think that to wobble, you have to have something to cause a side to side motion to begin the whole process. If the roadway causes it, the wobble will be short lived, like when you change lanes or cross a slight bump. But if you have a tire/wheel causing the side to side motion, you can never be fully rid of it until you retire the problem. (on my 85, it's always been the rear tire) (and I have been able to see the side to side run out of the used tire) Up until then, the best you can hope for is to minimize the effects by tweeking all the bearing areas etc, or adding a dampener, and/or stiffer fork braces, and/or frame braces, and so on.

:confused2:

 

[dannymax]

Try putting the bike on center stand, start it, put it in about 2nd gear and let it idle along with the rear wheel up. Go back and with plenty of light to see, watch the 'run out' of your rear wheel/new tire combo. I'll bet you'll be amazed at how much that new tire DOESN'T align side to side. It'd only take the smallest fraction of an inch of run out to create a very nasty tendency to tank slap at the front after applying length vs weight physics. I guess if you could test the front similarly, you might have a problem there, but much harder to test.

I think the reason the tank slapping intensifies during braking or slowing is because when you first start applying slowing force and the front end becomes heavier, it also starts adhering that much better to the roadway, causing any minute wobbling to come clear up the forks and into the handlebars, instead of being somewhat absorbed by roadway slippage. ???

Proper head bearing and wheel bearing adjustment and condition is a MUST, but I still think that to wobble, you have to have something to cause a side to side motion to begin the whole process. If the roadway causes it, the wobble will be short lived, like when you change lanes or cross a slight bump. But if you have a tire/wheel causing the side to side motion, you can never be fully rid of it until you retire the problem. (on my 85, it's always been the rear tire) (and I have been able to see the side to side run out of the used tire) Up until then, the best you can hope for is to minimize the effects by tweeking all the bearing areas etc, or adding a dampener, and/or stiffer fork braces, and/or frame braces, and so on.

:confused2:

Totally agree with you JF, rear wheel runout could definitely be a culprit. I mounted some Shinko Tourmasters a couple weeks ago and noticed that the tire was down in the bead in one area of the rear tire, causing about 1/4" of lateral runout in that area. I ran it up to 115 and only had a slight buzz in the mirrors, otherwise the front end stayed rock solid. So again, what affects one bike doesn't affect another.
BTW I mounted a 170 instead of the stock 150, which prolly accounts for the slight bead pinch. I'm taking the wheels off for powdercoat and will fix the issue then.
So, with my bike anyway, rear wheel runout didn't turn into a wobble. 'Course I may have only been a couple mph's from one, I don't know. :confused2:
The front wheel can be checked for runout by looking down on the tire at about 30 mph. Just be careful with the throttle when you do that!

 

[naughtyG]

All really good info guys - I shall also check my brand new Shinko 170's runout when I'm near the bike next.

My hunch is still on the worn head bearings as the main culprit - we will find out soon (on my bike anyway).

I would still like to hear from more newer max owners - let's say 2000 and up with less than 10,000 miles to see if ANY experience the high speed wobble as if none did, it would confirm that the design is sound and the problem is definitely due to wear and tear and therefore can be eliminated by proper maintenance.

 

[jfeagins]

My 85 never had any real tendency to tank slap until I had it up into the 130mph range even with a bad back tire. Overtightening or snugging the head bearings has caused a slight side to side motion at speeds under about 45mph. I may have a slightly bent wheel - all other bearing check out fine.


A friend of mine a little north of here is threatening to order his new 09 any day now. It'll be interesting to see how much better they handle than this original generation. Time will tell that story.

One thing's for sure, I bet Mother Yamaha addressed this handling problem specifically in their newer design. What'll you bet?

:eusa_dance:

 

[82ndCowboy]

My 06 has never high speed wobbled. I've had it up to 115 two or threee times. And 120 once.
I did have minor low speed wobbling around 40mph, but that was cured with a new front tire and snuggin up the head bearings.