'03 CRF450 Suspension Problems

[MCP486]

Hi,

I bought a 2003 CRF450R on Saturday, and rode it for the first time on Sunday......Ouch! My wrists were killing me. I weigh 150 without gear, and it felt really harsh.....Small Jumps, 50 foot jumps, weird in the whoops. I thought that it was too stiff, so I backed out the compression and rebound 2 clicks on both ends, and now I can feel it blow through the soft part of the travel, and transmit everything into my body. So maybe it's too soft, and riding too low in the travel? I thought I was going to be too light for the stock suspension, but maybe not. Anyway, I realize that I will probably need a revalve, or different springs, but your help is appreciated.

Thanks,

Matt

 

[afm_722]

Hey Matt, you lucky dog! I would give the suspension a little more time to break in. Go soft on the clickers is not a bad idea for the short term.

The major chassis changes for 03...increased spring rate in the rear (and linkage change), is putting more weight bias on the fork. With your weight, you could very well have too much spring rate. I definitely don't think you have too little!!

Bottom line is ride it a few more times to let it break in thoroughly. Experiment with a little more rebound instead of, as you said, you backed it out. Generally, when you soften the compression, leave the rebound alone to feel the affect of just that change. Then, add (turn clockwise) a click or two of rebound to keep the suspension from rebounding too quickly because of the softer compression settings.

Ride it some more you lucky dog, let it break in some more and try a little more rebound.

 

[marcusgunby]

Like afm said-give it more time-the showas take at least 15 hours to bed in.Then look at correct springs for your weight.

 

[MCP486]

Thanks guys.

Matt

 

[shockdoc]

Sounds like you you may have R/S fork binding issues. Check & make sure that it's centered on the axle right.


doc

 

[MCP486]

I thought that may have been the problem too, but I loosened the right side pinch bolts and compressed the forks, and that wasn't the problem. I am using the full travel, I can see the marks on the forks, and on the bottom of the shock where it is hitting the bumper.

Matt

 

[shockdoc]

Well, usually on the Honda's, loosing the frt. pinch bolts and then just pushing up & down on the forks won't center the R/S fork. It's best to leave the bike on a stand then loosen the 2 R/S bolts first. Then carefully tap a straight blade screwdriver into the slot between the 2 bolts and it will usually center itselt. If not just use your thumb & fingers and push & pull on the bottom of the fork & that will work. If all thats good maybe check your fork tube height in the clamps. If they are to far down the forks will feel harsh. Hope some of this helps.

doc

 

[dell30rb]

shockdoc, if i were to raise my forks in the clamps (now they are flush) do you think they would get a little bit softer?

 

[shockdoc]

Yes....that puts more weight on the frt. end thus making them feel softer.


doc

 

[dell30rb]

hey doc, your pm box is full

 

[afm_722]

Raising the forks could make the front end feel more planted, but the general term "softer" I don't quite agree. Moving the fork up should primarily be done to balance the chassis and help turning. If you go too far, you could end up putting too much weight on the front and then the forks will feel harsh. Generally, when you move the fork up in the clamps you'll want to add a little compression and soften the rebound so the fork remains plush.

Again, experimenting is the best method. On my Kawi (with stock pull rods), My forks are raised 10mm and it makes a noticeable difference. To compensate for the extra weight up front, I added a two clicks of compression, and softenened the reboud two clicks. I did the clicker changes after I moved the fork up.

Happy tuning...

 

[shockdoc]

Well, if you disagree then why after you raised YOUR forks & put more weight on the frt. end did you stiffen the comp. & speed the rebound? Maybe because they were softer and riding down in the stroke more? Just wondering.


doc

 

[John Curea]

MCP486

At 150lbs., the stock springs are way too stiff for your weight. The stock fork springs are .47, plus add the ICS into the equation and you have springs that equal just over .49kg/mm.

At first we thought that the ICS (inner chamber spring) only affects preload, but after doing the math and having a really cool spread sheet done up by a contributing enthusiast, we have found out that the ICS impacts overall spring rate.

Even after doing the hydraulic reduction of 34mm (ICS piston) to the 12mm piston rod, and taking into account that the ICS piston moves 40mm during full fork travel. An ICS with a rate of 2.2kg/mm equals about .025 of added spring rate.

This ought to get a good discussion going........ :thumb:

Take Care, John

 

[shockdoc]

I'm happy to see you came to those conclusions too John. I have been using lighter ICS springs for some time now and have had other tuners disagree with me. I 'm just not smart enough to be able to put it all down on paper to make any sense so.....thanks again.


PS.....After re-reading MCP486's initial post and seeing that he was 150 lbs. (which I missed the first time) it was obvious he needed lighter springs frt. & rear.

doc

 

[afm_722]

The term "softer" could be defined several ways, but riding further down in the stroke as you put is a bad definition. My forks would ride down further in the stroke (as a result of raising the forks...too improve turning primarily), but instead of being plush they were harsher. Thus the increase in compression and softening of rebound...

 

[marcusgunby]

Afm would it be better in this case to talk in terms of weight bias-the forks are higher in the clamps which puts more weight on them.So the adjustments made are to counteract the bias change.

 

[maui]

The forks on my 02 crf450 were very harsh and I weigh 175. Changed the fork oil volume from 425cc to 390 cc and now they are much more plush.Twin chamber showa forks often have a harsh midstroke until you lower the oil level. Learned this in mxa magazine and it works.