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Old 11-15-2012, 09:39 PM   #71146
Feelers
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Quote:
Originally Posted by johnkol View Post
By "flexible" I mean large amplitude oscillation modes, and by "uncontrollable" I mean no targeted damping of said oscillations.
Quote:
Originally Posted by johnkol View Post
The frame flexes are very evident once you step on a (even mildly) rough dirt road: the wheels are not tracking on the same longitudinal plane, they oscillate left and right all the time, independently of each other. This phenomenon is not due to suspension components (which only allow movement on the vertical plane), but it's the frame flexing from the forces impacted on it from the road imperfections.

You can experience the same thing on asphalt when you cross a longitudinal seam at a shallow angle: the bike will wiggle a bit as you cross the seam; it's not as pronounced as on a dirt road, but you can get an idea of what is going on.
Quote:
Originally Posted by johnkol View Post
Modern mechanical design practices necessitate CAD usage and FEA modelling, and these tools allow the designers to precisely calculate resonant frequencies of the frame and apply appropriate damping. The DR frame exhibiting large amplitude resonances that are essentially undamped means...
So, the high amplitude resonant frequency vibrations/oscillations happen mainly on dirt? So, they are not RPM dependent? They must be dependent on evenly spaced bumps then - like a washboarded road... But then, a single bump over a seam can cause it... So everything causes this?

Can you give us an RPM to look for this phenomenon so we can see what you mean - if it's RPM induced. Would I be able to put my bike on a stand and rev it to a certain RPM and watch the tail wag? Is it driveline related? Would I have to be engaged in gear?

The seam thing is fully suspension related as the tire is airborne for a split second during the drop. When the tire hits the ground, it's in a slightly different spot than it otherwise would be and feels like the tire skipped. My CBR does this pretty badly. That small force probably also causes the forks to twist a bit as they are pretty twisty. The wheel and handlebars are not rigid at all as you can see if you've ever tried to fix twisted bars after a fall. And riding on a seam is hardly enough force to flex a frame.
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Old 11-15-2012, 09:48 PM   #71147
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[QUOTE=johnkol;20054805] don't seem to get any feedback from the bike... In short, it feels like I'm seating on a giant jello, with no tactile sense of what the bike is doing. /QUOTE]
Sounds exactly like the stock suspension. Easily fixed with proper springs and valving.
You can feel the frame flex? But you can't get any other feedback from the bike?

I agree that you should get yourself something else because you will never believe that the DR can be a fabulous bike.

*************************************************

Alright guys, I'm outta here!
Leaving tomorrow at daybreak to spend 9 days in and around Death Valley.
If I can get my frame to flex enough to be a problem I'll be sure to let y'all know.
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Old 11-15-2012, 09:58 PM   #71148
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Quote:
Originally Posted by procycle View Post
You can feel the frame flex? But you can't get any other feedback from the bike?

I agree that you should get yourself something else because you will never believe that the DR can be a fabulous bike.

*************************************************

Alright guys, I'm outta here!
Leaving tomorrow at daybreak to spend 9 days in and around Death Valley.
If I can get my frame to flex enough to be a problem I'll be sure to let y'all know.
Yeah, he obviously has his mind made up and needs something else that he might have positive preconceived notions of. It sounds like he had his mind made up before he bought it, and is just blaming the frame so that he is forced to get rid of it. Whatever.... It doesn't make me any less happy with my own DR.

And, have a great time in Death Valley!!!!!!!!!!!!!
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Old 11-15-2012, 10:02 PM   #71149
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Quote:
Originally Posted by TRAVELGUY View Post
Hey guys am I missing something? Doesn't the stock rear shock only have rebound adjustment?
No, the stock shock only has compression damping; rebound damping is controlled by a collar at the bottom of the shock assembly. You can take a look at the manual if you don't believe me.
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Old 11-15-2012, 10:18 PM   #71150
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Death Valley Ride

Hello,

Man, would I like to join you in Death Valley. Great time of year.

I cannot due to the fact that you helped me lower my dr so low,( thanks, perfect.flex is all gone) , that the ambient temperature related to the low altitude and high frequency of my ass falling over the bars on evenly spaced bumps will dampen my spirits.
Thus I will stay home in hot oscillating bubbling water and drink some spirits instead.
I hope you have something other to ride than a slinky, oops, dr650.
Have a wonderful time from all.

Heirhead
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Old 11-15-2012, 10:30 PM   #71151
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Quote:
Originally Posted by procycle View Post
*************************************************

Alright guys, I'm outta here!
Leaving tomorrow at daybreak to spend 9 days in and around Death Valley.
If I can get my frame to flex enough to be a problem I'll be sure to let y'all know.
Have fun, In early january this year, I rode around death valley for three days on my 06 dr650 - had a great time!

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Old 11-15-2012, 10:40 PM   #71152
johnkol
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Quote:
Originally Posted by Adv Grifter View Post
I believe you refer to Honda's "Tuned Flex" technology.
No, "Tuned Flex" was something else. Technically similar, but conceptually different.

The flexible frames on the XRs were a huge success, as sales and longevity of that series testify.

Quote:
Originally Posted by Adv Grifter View Post
IMHO, the DR650 does not really have the HP to initiate noticeable frame flex.
Nothing to do with power; the flex is due to lateral forces, not longitudinal ones.

Quote:
Originally Posted by Adv Grifter View Post
YES! It will move around riding of rough dirt roads! It weighs up near 400 lbs., it's not a 260 lb. race bike.
No, it shouldn't "move around", weight has nothing to do with this. Think about it, if weight was a factor, then given the fact that a 20-lb mountain bike moves a tiny bit, then my 240-lb KTM should be flexing like a rubber band; it does not.

The frame is always constructed so as to handle the stresses applied to it -- and the amount of stress also depends on the weight of the bike. So a heavier bike means higher forces applied to the frame, which further means that a more stout frame needs to be constructed. The end result is the same: no "moving around", irrespective of weight.

Quote:
Originally Posted by Adv Grifter View Post
Feel your handlebars .. they are rubber mounted ... and low and behold ... they FLEX!
Pegs are rubber mounted too. Different sensation, nothing to do with frame flexing.

Quote:
Originally Posted by Adv Grifter View Post
The '92 Husky you spoke of brings back some memories ... or nightmares? Was this magic Husky a 2 stroke?
It was a 2T Swedish design.

I got a '91 Honda CR125 after this; it was a really good bike, but nowhere near the WR250.
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Old 11-15-2012, 11:11 PM   #71153
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Cool2

Quote:
Originally Posted by procycle View Post
*************************************************

Alright guys, I'm outta here!
Leaving tomorrow at daybreak to spend 9 days in and around Death Valley.
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Quote:
Originally Posted by Threewheelbonnie View Post
"BTW, I don't do style. It's a dirt bike, not some girlie dress-up thing." -
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Old 11-15-2012, 11:26 PM   #71154
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Something's wrong Frank. I have chicks jumpin' on my DR at stop lights all the time.

yeah right
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Old 11-16-2012, 04:17 AM   #71155
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Quote:
Originally Posted by heirhead View Post
Hello,

Man, would I like to join you in Death Valley. Great time of year.

I cannot due to the fact that you helped me lower my dr so low,( thanks, perfect.flex is all gone) , that the ambient temperature related to the low altitude and high frequency of my ass falling over the bars on evenly spaced bumps will dampen my spirits.
Thus I will stay home in hot oscillating bubbling water and drink some spirits instead.
I hope you have something other to ride than a slinky, oops, dr650.
Have a wonderful time from all.

Heirhead
this thread is starting to get fun ...........good stuff Heir
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Old 11-16-2012, 04:28 AM   #71156
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Quote:
Originally Posted by procycle View Post
*************************************************
Alright guys, I'm outta here!
For anyone who's interested here's a link to the SPOT tracking page

http://share.findmespot.com/shared/f...jBGuarSOcaHZNc
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Old 11-16-2012, 04:59 AM   #71157
doug s.
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Quote:
Originally Posted by Escaped View Post
There is no frame flex problem.





Sent from my SAMSUNG-SGH-I317 using Tapatalk 2
+1. whatever problem johnkol is having w/his bike he has mis-diagnosed it, imo he should try one that has been properly set up, and doesn't have a cracked weld/tube/etc... his bike is obviously bone-stock, and/or has other unknown issues...

doug s.
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Old 11-16-2012, 05:28 AM   #71158
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Quote:
Originally Posted by doug s. View Post
+1. whatever problem johnkol is having w/his bike he has mis-diagnosed it, imo he should try one that has been properly set up, and doesn't have a cracked weld/tube/etc... his bike is obviously bone-stock, and/or has other unknown issues...

doug s.
+2
I'm certainly not an engineer but, some of his technical assertions are highly suspect. JMHO
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Old 11-16-2012, 05:32 AM   #71159
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Quote:
Originally Posted by doug s. View Post
+1. whatever problem johnkol is having w/his bike he has mis-diagnosed it, imo he should try one that has been properly set up, and doesn't have a cracked weld/tube/etc... his bike is obviously bone-stock, and/or has other unknown issues...

doug s.
Yup, anyone that is going to complain about the bike's handling while not first addressing the woefully inadequate suspension is someone not to be taken seriously.
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Old 11-16-2012, 06:33 AM   #71160
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Quote:
Originally Posted by johnkol View Post
I'd rather leave it as is and enjoy it for what it is: a cheap, reliable machine.
I think we are done here.
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