Suspension front end wobble - Kawasaki Ninja 1000 Forum
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post #1 of 24 Old 11-23-2019, 11:51 AM Thread Starter
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Suspension front end wobble

I thought I would post here since I have not solved my problem.


I have a wobble in the front forks when accelerating rapidly around the 80-90+MPH. I have gone with a higher profile rear tire as many others have.


So far I have tried slightly stiffening the upper spring preload while also slightly increasing the rear preload. This helped but the wobble is still there.


I am not an expert and have read a lot about setting up my suspension. I do not have a second set of hands so I have not done that yet. I believe I will need to but do any of you have an idea on where I should look. At first I thought I had too little weight on the front end but then after thinking of the higher rear tire I was not sure if I now have too much rake.


Thanks to all that have some insights here...

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post #2 of 24 Old 11-23-2019, 12:07 PM
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What is your weight? I see you have agt's, but how old are they? How many miles on them?

I found my agt a spec tires to be a complete motherfucker to set the bead on. It would have been very easy to not have a 100% beaded up tire.

Is this wobble there at all times, or just at that 80-90 spot?

Last edited by rcannon409; 11-23-2019 at 12:10 PM.
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post #3 of 24 Old 11-23-2019, 12:16 PM Thread Starter
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Quote:
Originally Posted by rcannon409 View Post
What is your weight? I see you have agt's, but how old are they? How many miles on them?

I found my agt a spec tires to be a complete motherfucker to set the bead on. It would have been very easy to not have a 100% beaded up tire.

Is this wobble there at all times, or just at that 80-90 spot?

The rear tire is about 6 months old and the front is about 3. I weigh 163 lbs. I have put about 1500 miles on the pair. The wobble is just on hard acceleration at higher speeds. As soon as I get off of the throttle it tracks perfect.

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post #4 of 24 Old 11-23-2019, 12:23 PM
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Has this wobble always existed with these tires or did it just develop? An improperly mounted or non-concentric tire can certainly cause this problem. So too could an internal defect. If you can get the bike on a lift, spin the tires and check their run-out.

Tire pressure, tire balance (did you lose a weight?), damaged rim, looseness in the steering head, wheel bearings, or swingarm pivot.

The always-excellent Kevin Cameron just did a piece on this:
https://www.cycleworld.com/motorcycl...h-wobble-talk/
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post #5 of 24 Old 11-23-2019, 01:54 PM
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Check air pressure, steering head bearings, check your sag front and rear!! A wobble is a symptom of something being worn or not set up correctly. The fact that it only happens under hard acceleration can also mean the front end is getting light....you are 163 pounds so that is possible. If everything checks out, install a steering damper....
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post #6 of 24 Old 11-23-2019, 08:38 PM
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That sounds like real, legit headshake. A bad component will usually not appear...then go away. Usually a bad part might get worse, at speed, but if you pay attention, it will show itself at other speeds.

Now the thought is why. If you are taking these bikes up to speed, you have to know what condition the bearings are in . Wheel, swingarm, shock linkage and steering head. If a person cant do it themselves, pay someone to do it. Not doing/knowing and just hoping is foolish, stupid, and dangerous. Not directed at you. That goes for all of us.

Raising the back end, with a 190/55, tpis a great mod. However, doing so sharpens geometry and cuts into the margin of ...not safety so much, but call it set up error. Sharper geometry relies on the suspension to do its job properly, and set for you. The tire made a huge change in height. Your new taller tire, with its new, deep tread, raised the back end by at least 8mm, if not more.

The best idea would be to set up the suspension properly. Set the front and rear rider sag. If the back end is too stiff, or does not sag enough, it can cause this to occur.

A quick thing to try would be to lower the back and just leave the front as-is. This will change something. It should make it better. If it makes it worse, thats fine to, but be ready. You know what not to do. As you add preload and make the back end more stiff, you usually end up needing to add some more rebound damping in to stay as you were. Not much, try a 1/4 turn. Then reduce that 1/4 to 1/8. Raising both ends will do pretty much nothing.

A damper is a great mod, and everyone should have one. They are awesome. Much better to be able to use them rather than to "need" them. Adding one now is a band aid over something else. Hundreds of these ninjas have made this change with no issues, so its better to find out whats up with yours.
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post #7 of 24 Old 11-23-2019, 09:26 PM
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At some point a subscription to Dave Moss Tuning will be recommended. DM lives for this stuff.
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post #8 of 24 Old 11-24-2019, 09:34 AM
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Quote:
Originally Posted by rcannon409 View Post
That sounds like real, legit headshake. A bad component will usually not appear...then go away. Usually a bad part might get worse, at speed, but if you pay attention, it will show itself at other speeds.

Now the thought is why. If you are taking these bikes up to speed, you have to know what condition the bearings are in . Wheel, swingarm, shock linkage and steering head. If a person cant do it themselves, pay someone to do it. Not doing/knowing and just hoping is foolish, stupid, and dangerous. Not directed at you. That goes for all of us.

Raising the back end, with a 190/55, tpis a great mod. However, doing so sharpens geometry and cuts into the margin of ...not safety so much, but call it set up error. Sharper geometry relies on the suspension to do its job properly, and set for you. The tire made a huge change in height. Your new taller tire, with its new, deep tread, raised the back end by at least 8mm, if not more.

The best idea would be to set up the suspension properly. Set the front and rear rider sag. If the back end is too stiff, or does not sag enough, it can cause this to occur.

A quick thing to try would be to lower the back and just leave the front as-is. This will change something. It should make it better. If it makes it worse, thats fine to, but be ready. You know what not to do. As you add preload and make the back end more stiff, you usually end up needing to add some more rebound damping in to stay as you were. Not much, try a 1/4 turn. Then reduce that 1/4 to 1/8. Raising both ends will do pretty much nothing.

A damper is a great mod, and everyone should have one. They are awesome. Much better to be able to use them rather than to "need" them. Adding one now is a band aid over something else. Hundreds of these ninjas have made this change with no issues, so its better to find out whats up with yours.
Spot on and great advice! My guess is combining the taller rear tire with additional preload in the rear may be your issue. At 163lbs. you may have to back that out. Adjust your rider sag at both ends and shoot for sag to be 30-33% of total travel and assuming you have no other issues like worn steering head bearings, it should fix your issue.
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Last edited by CRFan1; 11-24-2019 at 09:38 AM. Reason: Add info.
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post #9 of 24 Old 11-24-2019, 10:28 AM
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Rikifumi, i should have added the Dave Moss recommend. I know you have a lot of experience. If a person signs up as watches a few videos, i believe they can make their suspension a hell of a lot better and probably learn enough to deal with problems. Although he might not deal with your specific bike (so far), a viewer will see the pattern. Ac

His videos are excellent and they dont try to upsell.

The factory settings are a compromise that will work for anyone. That never works well for any specific user.163 pounds is at the lighter end of that "average rider" CRfan1 mentioned raising the back end, and thats right on.That was the last thing you needed to do.

That is the cool part about setting up motorcycle suspension. A bad reaction is as good as a positive reaction. Knowing what not to do helps as much as knowing what to do.
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post #10 of 24 Old 11-24-2019, 01:46 PM
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I would start by checking the smaller things before getting into any parts.

What front tire pressure are you running? - I've found that too low pressure can cause some shakes.

When the bike is lifted, spin the wheel and see if it is still spinning straight.
Reset the settings on your forks as well. See if it is the same.
When the bike is lifted, you can also check for the bearings if you steer it side to side/lock to lock. Slightly flick it from side to side and see if it bounces back after hits the locking point.
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