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Discussion Starter · #1 ·
I had noticed it a couple of days ago and I blamed it on the fairly strong wind we were having . Now today , no wind at all and on a good stretch of road , I pushed the bike to 150 km/h and started to feel very un comfortable with its behavior / handling . Very wobbly and like bouncing up and down . The tires are look ok .
Could it be a wheel baring or steering stem baring going ?
 

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http://www.ktmduke390forum.com/forum/ktm-duke-general-discussion/24618-duke-starts-wo

Get the front end off the ground by putting something under the motor. Now- grasp the front forks and see if you can feel movement by rocking the forks foreward and backward. If you can feel any movement- your stem head bearings are out of adjustment or kaputnick,
Hold the forks with one hand, then grip the front tire with the other hand, and see if the wheel rocks sideways- if it does, your wheel bearings are shot.
Do not ride at elevated speeds until this is corrected.
Hope this helps.
 

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I know of a few 390's with bad head bearings at low miles. Check as stated above.
 
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Discussion Starter · #6 ·
Will do that , this week I'll get my Andreani fork kit delivered and hope to be able to have it fitted as soon it arrives . Guess that is the perfect occasion to have the bearings on both stem and wheel checked
 

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Will do that , this week I'll get my Andreani fork kit delivered
You can't be too far behind @cajun22 on mods now :)

Needless to say, worth checking the rear wheel bearings and (although hugely unlikely at low miles) swing arm bearings while you are at it.

Last bad wobble I had (on my Duke2) was caused by the rear tyre. That was really easy to diagnose though, as it started right after I fitted it (it was a used item, so resold it on ebay and bought something else :) )
 

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Didi from the German 390 forum had an issue with corrosion in the steering head bearings of his 2013 Duke, after two years of exposure to the damp German climate. His photos showed rather alarming rust in the bearings, strongly suggesting that they had not been greased during factory assembly.

Zippy replaced the head bearings in his bike after an incident which put severe loads on his Duke's front end. He found that that a set of replacement OEM bearings from KTM is remarkably inexpensive.

All Balls Racing, it was subsequently discovered, has a set of tapered roller bearings that will fit the 390, for those who would like to upgrade. The reference is:

Top Bearing - 99-3515-5
Bottom Bearing - 99-3521-5

Fork conversion All Balls Racing
 
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Neither 390 variant uses bearings at the swingarm pivot. Instead, a set of inner and outer bushings is fitted at each side. A lengthy thread on the 390 forum discussed the discovery that these bushings are fitted DRY at the factory. Premature wear was beginning to show. There are photos and a how-to explaining a step-by-step guide to greasing these bushings. A very good idea, IMO, something I will get around to doing before long if I can stop riding and modding long enough.

There was some talk by Matt Shreiner of Formula390 of developing a needle bearing kit to replace the bushings. To date, however, the rumored kit has not materialized.

All Balls Racing, BTW, carries needle bearings in all sizes. If someone were to disassemble the swingarm, then take careful measurements of the bolt, bushings and socket, I think the likelihood is great that ALL Balls would have appropriate needle bearing replacements. This is one of the entertaining aspects of owning a Duke/RC - always another upgrade project on the horizon!

http://www.rc390-forum.com/forum/wh...arm-bushings.html?highlight=swingarm+bushings
 

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Luc the Engineer/Tutorial guru would be the perfect man to do this! Yes!!
 
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Discussion Starter · #12 ·
You can't be too far behind @cajun22 on mods now :)

Needless to say, worth checking the rear wheel bearings and (although hugely unlikely at low miles) swing arm bearings while you are at it.

Last bad wobble I had (on my Duke2) was caused by the rear tyre. That was really easy to diagnose though, as it started right after I fitted it (it was a used item, so resold it on ebay and bought something else :) )
I only have about 3K on the clock and hence still on the stock front and rear tires . My best bet is that bearings on either front wheel or steering stem are causing the wobble . I'd prefer to buy the " upgraded " bearings from all balls but I'm afraid they will take some time to reach me and would prefer to take advantage of the fact I have to remove the the fork legs anyway to swap over the cartridges .
 

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Discussion Starter · #13 ·
Well... If we get a crappy weather weekend, I might do a swingarm pivot tutorial and take some measurments for the needle bearing
Luc .. you could perhaps do a steering stem bearing replacement and fork cartridge replacement tutorial too when you're at it ? :)
 

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Yves, The OEM steering stem bearings from KTM work well, and would probably be durable IF GREASED during assembly. Perhaps your bearings need adjustment, so while the Adreanis are being fitted to your forks, perhaps you could disassemble the steering stem, grease the bearings and reassemble, tightening to spec. Your local KTM dealer might have those bearings in stock if you want to change them - apparently they are not expensive. I think you are right that the All Balls tapered bearings would take much longer to reach you than using the readily-available OEM bearings.
 

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Discussion Starter · #15 ·
Yves, The OEM steering stem bearings from KTM work well, and would probably be durable IF GREASED during assembly. Perhaps your bearings need adjustment, so while the Adreanis are being fitted to your forks, perhaps you could disassemble the steering stem, grease the bearings and reassemble, tightening to spec. Your local KTM dealer might have those bearings in stock if you want to change them - apparently they are not expensive. I think you are right that the All Balls tapered bearings would take much longer to reach you than using the readily-available OEM bearings.
Will , that was exactly my idea : Whilst I'm dismantling the fork legs I'd like to have a look at these steering stem bearings . I will check with the local dealer for availability for both front wheel bearings and these steering stem ones .
 

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I only have about 3K on the clock and hence still on the stock front and rear tires . My best bet is that bearings on either front wheel or steering stem are causing the wobble . I'd prefer to buy the " upgraded " bearings from all balls but I'm afraid they will take some time to reach me and would prefer to take advantage of the fact I have to remove the the fork legs anyway to swap over the cartridges .
Where did you find All Balls bearing for the D390? I checked their site and they don't even have KTM's listed.
 

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Discussion Starter · #17 ·
Where did you find All Balls bearing for the D390? I checked their site and they don't even have KTM's listed.
From an earlier post in this thread : You shouldn't even ask who posted it .. " Encylcopedic Diploman " aka " the man who knows more than google " of course

Top Bearing - 99-3515-5
Bottom Bearing - 99-3521-5
 

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On that surreal note, I need to go and get a strong drink.....

BTW, Tony, go to the All Balls site (what a great name!), enter bike info in the "Find Fork Conversion Bearings" frame, then scroll WAY down, past Honda and Kawasaki, then you will find the KTM Duke and RC just before Moto Guzzi.
 
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http://www.ktmduke390forum.com/forum/ktm-duke-general-discussion/24618-duke-starts-wo

On that surreal note, I need to go and get a strong drink.....

BTW, Tony, go to the All Balls site (what a great name!), enter bike info in the "Find Fork Conversion Bearings" frame, then scroll WAY down, past Honda and Kawasaki, then you will find the KTM Duke and RC just before Moto Guzzi.
Howzabout a really nice Single Malt- can't tell you what the stuff is, (the label is in Gaelic).....
 
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