Dirt Bike Modifications Forum

Just got a new 2007 CRF 450 honda, I need some guide lines on were to start when it comes to tuning in a suspension. I am 5' 11" and weigh about 150.  

here is what the latest motocrossactionmag says, swap the stock .47 springs for stiffer .49's then take 5 cc's of oil out of each fork (stock is 384cc) on this setup they ran thecompression on 10 clicks out and rebound on ten clicks out.

shock:sag at 100mm,low speed compression on12, high speed on 2 out(hex thing on top of shock)  then the rebound on 10.

What is taking 5cc of oil out of the forks going to do? What were the weight of the test riders? The suspesion is to stif as it is, but the suspesion is not yet broke in. I was told to brake it in before I make the final tune because a friend said that the suspesion will change until the suspesion settles and wears in. Right know I have my forks set at 12 clicks back on compression and 10 on rebound. Rear shock is set at 10 low speed compression and stock on high speed and 10 on rebound, sag at 1.5 inches. Not shore what that is in mm.

The bike fills tall when I sit on it. Rear shock stiff. What to do next?

The bike probably still feels tall becuase you might be short-legged. You dont set the sag so the bike doesnt feel tall anymore. Thats not the purpose.

Taking 5cc's of oil out will soften up the last part of the travel I believe. The more oil you have in there, the more force can be applied to compress the fork tubes before it bottoms out.

I set my race sag to 4". Spec is 3.9", bike sag is .4 to 1", how do you set race sag and bike sag so that they are both in spec? I have tryed I cann't do it. My race sage is 4" and bike sag is 2". Which one is more important?  

i do not know the answer to the last question but the stiffer fork springs will resist bottoming better while taking out 5 cc's of oil will make it more supple over the small and medium size bumps. theis is just what motocrossactionmag says but i beleive whatever they say cuz i used their suspension settings on my yz250f and it was sso much better than anything i tried out.

If your numbers are correct; with the race sag at about 4" and static sag at 2" it means your shock spring is too stiff for your weight.  How much do you weigh with gear on?  That seems like a lot of static sag.  Most bikes tend to be sprung too soft.

To correct you would need to get a softer rate spring.

With all my gear I weigh about 170-175. So static sage is the bikes rear shock free play, in my case 2". What I don't get is how do you get race sage and static sage in to spec. I have race sage within spec but static sage is 1" to much. I dont see how a softer spring is going to solve the problem. Educate me if you will and I will ask my local dealer. What kind of problems will I have if I leave it at 2" of static sage?  

There is a good article on the site here about bike set up it covers suspension pretty good.  I'll try to get a link but I'm not great with all that stuff. Its under the "Tech" page "How to: Set up your bike"

Unless someone has changed the shock sping to a stiffer one in the past at your weight it should be close (most bikes come sprung for 180 lb riders).

But the reason it would take a softer spring (assuming yours is too stiff) is to get the right sag you have to back the preload off so much that there is little to none on it and it lets the weight of the bike sag it more.  To work correctly springs need between a minimum and maximum preload.

By going to a softer spring you have to put more pre-load into it to get the right race sag.  Because it has more -preload it also will hold up the staic weight of the bike more and you get less static sag.

Do you know if the spring on there was stock???

Here are a couple pages that explain it pretty well.

http://www.tootechracing.com/suspension_tips.htm Explains Race Sag

http://www.tootechracing.com/Static%20Sag%20Suspension%20Tip.htm  Explains static sag.

My bikes suspesion is stock. The bike is a new 2007.

How do you determine how soft of a spring to go. Is it a guessing game. I hope not because them springs are pricey. If I were to go with a new softer spring what brand should I look into? How do you determine if you bikes pre load is in spec? Is it that critical?

I think that you are right that the spring is to stiff because last time I went riding and went throw some whoops I was all over.

Do you have any tips on how to set up the forks correctly? Hopfully I dont have to buy new spring for it to.

Thanks for the links. I help me understand the right procedure for setting up the shock. I appreciate  it.

i would definately not go softer. you are a little heavier and if you are somewhat fast youwill not like it. your sag is off because it is ot set. it is much better to speak in millimeters as they are much more specific. theres 2 rings on the top of your shock and the top one tightens the bottom. loosen the top one up and then take a measuring tape(with millimeter)and measure from the rear axle straight up to the side panel. write that number down. then get a buddy and you sit on it while he measures from the same point on the axle straight up to the side panel. take the 2nd number and subtract it from the 1st fone and that should be your sag. if it is too low loosen the bottom ring on the top of the shock so it raotates up. generally 1 full turn is 3 millimeters, so remember where you started. keep the 1st number and check the sag with you on it until it is at 1 hundred millimeters. this is to get the best possible handling ad stability you can. and like i said earlier. get teh .49 springs and then take 10 cc out of the forks. teh stiffer springs will resist bottoming better while taking 10cc's out of the forks while make it plusher than stock through the whoops, chop, square edged bumps, jumps etc. this is what every ama national pro (all ama national pros do this) and all faster or heavier riders should do to their crf450's.

http://www.motocrossactionmag.com/ME2/dirmod.asp?sid=&nm=&type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F
516B4C10&tier=3&nid=DEB4FC80F93F46768CB9629FFEA106BF

I haven't had a Suzuki (dirt bike) since 1975; so I can't offer any advice on setup specifically for a Suzuki.

As I mentioned before though something doesn't seem right.  Most new bikes are setup for 180 lb riders (which is where you are at with gear I would say).  So if you have 4" of race sag with you on board; I don't see how you can be getting 2" of static sag.

Double check all the measurements again just to be sure.

hey wiat a secod. if i read right you have a crf 450, what bike do you have. is it an rm250. if it is the forget what i said, and im sorry for wasting your time if you dont have a crf450.

You may be right bubba177, I think I am wrong; I thought he was talking about an RM; it looks like he got a new CRF450 Honda.