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Rear Suspension setup ?
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Posted by: Marklx---------------------
Have a few rides on my '02 RM250, and am zeroing in on getting the suspension dialed. The biggest problem I'm having is with fast bumpy straights. The back end wants to kick sideways/come around a bit (way)more than I'm comfortable with. Also not great on acceleration bumps out of turns.
I've got the sag set seemingly correct, but can't keep the back down. I'm about 160 in street clothes, so the stock spring should be right. Backing off on compression seems to help, but I"m almost all the way out and the changes now seem minor.
While haven't spent any time fiddling with the forks, they seem great off jumps and braking into turns.
Any ideas on which direction to calm the backend down?
Mark
Posted by: dirt bike dave---------------------
My guess is the problem on the rough straights is related to your rebound damping - either too little or too much could cause that. How many clicks out are you on the rebound? I'll guess you have too much rear rebound damping, but you might want to experiment both directions.
IMO, the problem on the acceleration bumps could be related to having turned the compression clicker all the way out - i.e. you have too little low speed compression damping.
You are correct that as you turn the clikcers further out, each click makes a smaller difference.
Posted by: Fred T---------------------
Not an expert here but from what I have read in suspension tuning that is an indication of packing from too much dampening. Set compression back to where it was and take 2 clicks out on dampening. Packing happens when reaction is too slow and the shaft is not extending enough to handle the next hit so the shock is too compressed into the travel and it becomes harsh. Needs to be able to react a bit quicker I think. Still learning this myself. 
Posted by: Jeremy Wilkey---------------------
Mark,
The advise posted here already is good packing, is defiently your problem.. Try running your rebound softer. The major sysmpton is both a problem with accelarting, and side kick in faster sections.. Clearly packing from rebound!
Regards,
Jer
Posted by: Marklx---------------------
Thanks for all the input here. I have been dialing up the rebound damping, as the bike was bouncing initially when landing from bigger jumps. More rebound definitely helped with that, but apparently made the acceleration/kicking sideways problem worse. Guess I should start over at stock settings and try more compression and less rebound.
It seemed that backing off the low speed compression helped quite a bit with the accelerating out of bumpy corners, so that one has me confused. It would seem that less rebound and more compression would make that worse, but no harm in trying it. Hoping to hit the same track (Sunrise) that I rode last week, so should be a good yardstick to compare to.
Think I'll keep riding the same straight section at both extremes of rebound and work from there. I can better deal with a bit of bouncng out of corners, but the high speed stuff is scary:scream:
Mark
Posted by: dirt bike dave---------------------
The series of accelleration bumps and the long bumpy straight will cause the suspension to 'pack' if your rebound damping is too stiff and compression damping is too soft.
Essentitally, the soft comp. is allowing the wheel to use too much of it's travel and the stiff rebound is preventing it from returning in time for the next bump, getting worse and worse until all the travel is used and you lose control.
IMO, a little bouncing when landing from a single jump might not be a problem as long as it is easy to control the bike - it might be more important to get the suspension to handle the series of bumps. But everything is a compromise, and your personal preference certainly is a factor.
You might just want to go 3 clicks in on your compression and 3 out on your rebound from where you are now, and see how that changes things.
Good luck!
Posted by: Marklx---------------------
DB Dave,
You're right that a little bounce off a jump would be more tolerable. The high speed problem and the acceleration problem are slowing me a lot more than the jumping thing. Your theory makes sense so I"ll try it out tomorrow (assuming it doesn't rain).
Wish I had a video of what was happening, to see if I was blowing thru the travel/packing up. Now if I could just discipline myself enough to pull off the track and tinker. Everytime I go out there, the force takes over and prevents me from stopping
Mark
Posted by: Marklx---------------------
Managed to get in a little riding before a mutha of a wind storm blew thru Sunrise. I have never been in wind and dust like that. But anyways, before the Wizard of Oz, tried 2 clicks less rebound, and 2 clicks more slow speed. And the bike behaved much better. While a little more harsh on the small stuff, nothing to worry about, but much more predictable at speed and out of turns. Would've loved to have tried more settings, but had to leave before we were blown out.
Now if I could just learn how to twist the right grip a bit further and clear the nasties, that lack of rebound would be a non issue:think
Mark
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