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Old 10-28-2012, 07:29 PM   #1
BillyD OP
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Joined: Jun 2007
Location: San Mateo County Coast, CA
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Twisted Frame Cross Member KTM 640

Is this lower frame member supposed to be twisted like this?



I’ve bottomed the rear suspension a few times, but only once hard enough to pinch a rear tube and the rear tire only rubs the inner rear fender when running 140 Dunlop 606s

As such, I would find it difficult to believe that I’ve hit anything hard enough to twist or pull this cross member this much out of alignment. This leads me to believe that it was "Born this Way" and is the result of some final factory “adjustment” procedure. No cracks or others signs of distress are visible.




If you happen to have your 640 motor out of the frame, please take a look and let us know what your frame cross member looks like.

Thanks.
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KTM '08 690 RFR, '08 990Adv S (carbs), '07 640Adv, '03 540EXC, Ducati 851, Moto Guzzi 850 Lemans, Ercole & 2VT and Yamaha RD350.
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Old 10-28-2012, 08:04 PM   #2
gunnerbuck
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Did you have any trouble getting the swingarm off? I would think if it was bent from a hit the whole frame would of pulled in and pinched the swingarm/motor mount point so much that it would be difficult to get those parts to separate...

Likely that way right from the factory...
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Old 10-28-2012, 09:47 PM   #3
BillyD OP
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No problem getting the swing arm off (once I remove the pivot bolt ;-).
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Old 02-02-2013, 05:48 PM   #4
BillyD OP
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Lower Frame Cradle Tight Too

Perhaps as a result of the cross member being a bit tweaked, I noticed today that I had to spread the lower frame cradle rails in order to get the lower motor mount spacers in.

With the motor placed in the frame, it was impossible to get the lower spacers in between the motor cases and the cradle rails because there wasn't enough space.

With one spacer installed, I ultimately had to use two nuts on a bolt to spread gap between the rails to get the other side in.

Anyone else have this issue? I don't recall my other LC4 being anywhere near this tight.

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KTM '08 690 RFR, '08 990Adv S (carbs), '07 640Adv, '03 540EXC, Ducati 851, Moto Guzzi 850 Lemans, Ercole & 2VT and Yamaha RD350.

BillyD screwed with this post 02-02-2013 at 06:00 PM
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Old 02-03-2013, 12:16 AM   #5
Luke
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Just looking from the underside mine looks straight. The linkage puts a lot of force on that part of the frame, so it's not too surprising to me that it would bend.

I've never pulled the motor so couldn't tell you about the fit.
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Old 02-03-2013, 04:31 AM   #6
grimmboy
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Checked my 640, that lower is straight. i would think when it bottomed out it pulled the linkage and this lower member with it.

Cali has many motorcycle frame repair guys who should be able sort it.

Enjoy the day, Grimmy
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Old 02-05-2013, 08:57 PM   #7
BillyD OP
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Well, I stopped by EdGear's house on the way home tonight to take a gander at his pristine 640.

His frame cross member was straight as an arrow compared to mine. Am I going to do anything about it? Probably not.

It does beg the question, however, whether such variations in frame geometries and fitment could explain why some 640s seem to vibrate more than others. After all, that region of the frame is somewhat shaped like a tuning fork and, as we all remember from Physics 101, every tuning fork has its own resonance frequencies...

As I have noted on other occasions, this particular 2007 640 seems to buzz more than my two previous 640s (2000 & 2003). I installed the skid plate spaces on both of these other bikes and neither had a particularly tight fit. By comparison, it was impossible to get the spacers in without spreading the lower frame rails by at least a 1 mm on this 2007. If I remember correctly, the 2000 and 2003 had lower cradles made of steel tubing rather than the forged pieces on the 2007.

Having ridden EdGear's 2007 640 previously, I can attest to his bike also having less vibration than my otherwise identical 2007 640.

Maybe one day, EdGear will let me swap motors and then, perhaps, we would know for sure rather it is the motor or frame that makes my bike particularly buzzy.

In the mean time, I have a little science experiment underway to see if the vibes inherent in the 640 can be mitigated, but that's another topic (and why my motor was out of the frame in the first place.) See http://advrider.com/forums/showthread.php?t=863599

To be continued...
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KTM '08 690 RFR, '08 990Adv S (carbs), '07 640Adv, '03 540EXC, Ducati 851, Moto Guzzi 850 Lemans, Ercole & 2VT and Yamaha RD350.

BillyD screwed with this post 02-16-2013 at 02:46 PM
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