Showa shock spring "resonates" @ certain RPM

cr250john

Member
Jun 14, 2000
122
0
My '00 CR250 showa shock spring (5.2 kg/mm) hits a resonate frequency at a certain engine RPM and it vibrates like crazy. It happens while I'm sitting on the bike or on the stand at this "critical" RPM. The sag settings are correct for my weight.

I'm beginning to wonder if this vibration is translated into the bars causing fatigue of the arms. :think It seems to happen at an RPM I typically use.

Have you experienced this and is it typical for shock springs to do this? Is there a "cure" other than don't run the engine at the "critical resonant spring frequency"?

Your thoughts....
 

cr250john

Member
Jun 14, 2000
122
0
Thanks Marcus & Jeremy,

I'll put up with the vibration for now. I just happened to have the bike on the stand with the engine running and while revving up the engine, I saw the spring really vibrate at a certain RPM. Seemed to shake the whole bike.

Thanks for you thoughts!
 

Jaybird

Apprentice Goon
LIFETIME SPONSOR
Mar 16, 2001
6,449
0
Charlestown, IN
Marcus,
I've been thinking about filling my bars with silicone as well. Any cons, that you know of?
BTW....I was wondering about what was shaking the bejeeezuz out of me at times. I think I found the answer thread!
 

Murf

Member
Dec 31, 2000
96
0
resonant frequency

CR250John,
Keep in mind that when you are on the bike and riding with the spring compressing and decompressing that the resonant frequency will be changing, and therefore the likelihood of the vibration being transmitted up to the bars will be lower.
 

marcusgunby

LIFETIME SPONSOR
Jan 9, 2000
6,450
2
I originally had twinwalls on and they vibrated like an angry bee:scream: i now have TAG RM high bend filled with silicon and i hardly notice the vibes(and im real fussy)the only downside is its messy to do and they weigh about 1lb heavier-no real problems at all.:D
 

cr250john

Member
Jun 14, 2000
122
0
Re: resonant frequency

Originally posted by Murf
...when you are on the bike and riding with the spring compressing and decompressing that the resonant frequency will be changing, and therefore the likelihood of the vibration being transmitted up to the bars will be lower.

Right you are!
Just thought it was an interesting topic to add to the dirtbike vibration syndrome.

Thanks to all for your reply!
 

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