[dsn_klr650] digest number 204

[ephilride@aol.com]

In a message dated 6/2/00 5:28:41 PM EST, psprague@... writes: >>

[Tom Bowman]

PSprague wrote:

> To stiffen up the rear suspensionon my KLR 650 A13 I recently

replaced the

> oem shock spring with the PS 500/560 spring. The bike feels

better

> "planted" with no scraping on the panniers but a problem did

develop with

> the new spring: there is now a harmonic or resonnance problem

with the

> bike. Mostly this occurs between 40 and 50 mph, not dependent

on rpms (any

> gear). There is no wobble or weave but like a soft jackhammer,

about 3 to 6

> up and down pulses in the handlebars followed by an equal time

of

> smoothness, then the cycle of jackhammer/smoothness repeats.

Above 50 mph

> there is little or none. ............. > > I don't want to go back to the oem spring or spend the $$ for

a whole new

> PS shock. Anyone else had this problem? Any ideas??? > >>

And "Ole Knot" answers:

> Every system has a "natural frequency" (an infinite number

actually). The

> natural frequency of the system (your rig) is controlled by

its mass and

> stiffness (nat. freq = square root of stiffness divided by

mass) The

> damping (shocks) control the amplitude of vibration, not the

frequency. It

> appears that you have altered one of the frequencies that is

easily excited

> by random excitation (traveling down the road). This is a

simple explanation

> of a very complex phenomena. I would experiment with changing

the damping

> (increase) since you want to keep the stronger spring. Good

luck.

> > Knot - Whole lotta shakin' goin on.

Could it be that his bike has some out of round in the rear tire and the original rear spring/damping setup was so soft that it masked it? Or that there's some out of balance that was masked? Tom Bowman Atlanta A14 "Olive"

[JSherlockHolmes@aol.com]

In a message dated 6/3/00 4:17:02 AM Canada Central Standard Time, DSN_klr650@egroups.com writes: > Hey Tom, If you need to chat, or do lunch, or something, to help your mind. Or if you need help with something cuz you are tied up at the hospital, get a hold of me at my e-mail address. I live in Franklin on South 35th Street and would be happy to help out a fellow rider. Jim Sherlock JSherlockHolmes@...