cr250, harsh forks

[mxcrash]

Hi,

I'm new to this forum and have been soaking up the great info and tips people have on offer here and have learnt heaps, but now it's time for a question of my own.

I have a 2000 cr250 (since new) and have been doing mx for the last 1.5 years, and as we don't have the funds to upgrade it's now time to try and tune the suspension.

My weight is 80kg(176 lb) & height 6'2" I ride mostly sand, and the forks have been revalved recently to help with the small sharp chop (two staged comp stack I think it was called).

I've ensured the forks are aligned properly as per previous posts, and tried runing sag from 97mm-102mm .

The forks still are not quite to my liking. The other week I took 15ml of oil out of each leg and this made it quite a lot better, but after a quick ride today I tried adding 5ml to each leg, this required me to soften up the comp. by 4 clicks to handle the small chop but caused it to feel like it was falling thru the stroke and almost bottoming on the last braking bump as I enter corners.

My questions are

1. Would diff. fork springs help? harder or softer?
2. Is it safe to take out more than 15ml oil from the forks?
3. Would gold valves or the like help?
4. Could the rear shock or spring be the prob?

thanks

ash

 

[James]

In my 2000, I have been running 330 ccs of oil (the minimum I think) in each fork leg. Using minimum oil and setting the compression clickers almost full soft helps with harshness the best for me.

I still have the stock single stage valve but I have taken a shim out of the midvalve. I weigh quite a bit more than you and bottom some over jumps with the stock springs.

You said "almost" bottomed......does it bottom anywhere? Also, how are you setting the oil level and do you know if you at least have the minimum in there?

 

[mxcrash]

I was trusting the guy who serviced them that he put the std amount of oil in them.

To remove the 15ml I removed the forks unscrewed the fork cap (the largest nut) and pored out the oil, to add some back in I syringed it in thru the air bleed screw.

The forks slightly bottom thru a big g-out.

 

[dbrace]

The stock springs are close for your weight, i doubt they are your problem. Ensure that after setting you race sag you still have a minimum of 15mm free sag.
Perhaps you need to talk to your tuner so he can work with you or find one in Brisbane who has the experience to get the job done right. :clue:

 

[mxcrash]

As my details say I'm actually on the otherside of Aus in Perth and do deal with a guy who is the Perth dist. of a well know suspension guy who now seems to do a lot of work for KTM and WP.

I had previously checked various web sites and agree the springs (provided they haven't sagged too much) are close to ideal.

Re-reading my post perhaps didn't phrase the question correctly.

What I was really after was the peoples opinions based on their experience , would heaver springs and lighter comp. damping be the go, hence rely on the springs to hold up thru the deep whoops whilst the lighter damping would soak up the small sharp chop we have on a harder section of the track, or go lighter springs and heavier valving or just work on the valving and riding style ( or lack of ;) )

The reason I posted the question was I'm still getting a feel for how each adjustment affects the feel of the bike over various parts of the track and like most people I don't have truck loads of cash to try diff combos whilst continuing to bother the tuner with "what if questions".

I'm off to the shed to lower the oil level to James suggestions and then it's off to the track to compare.

 

[James]

It may be worth the time to completely drain the forks and measure in the correct oil amount. Do you have the owners manual? If not, I will be glad to look up the exact amounts and post them for you.

It is my amatuer opinion that if the springs are close to ideal for your weight now (assuming the web sites are correct), then stiffer springs would only make the intial travel more harsh and probably hurt the handling.

If you reduce the oil level and you start bottoming more than just big g-outs, then I'd say take your forks back to the suspension guy and say they aren't right (as dbrace suggested).

 

[mxcrash]

Wow I took out 45ml of oil of each leg which should bring it to approx 330, and the thing almost handled as good as my mates 03 cr250. I'm still fine tuning the settings, and balancing the front and rear but the improvement is unbelievable.

I have ordered a 50mm fork spanner which should arrive this coming week, so I should be able to fully drain the forks. I was also going to make up ta number of 1" pvc clips to easily change the effective oil height at the track.

One final question did spring to mind concerning the forks and the inner chamber oil level. The first time I removed the oil by borrowing the fork spanner, undoing the main chamber and tipping the required amount of oil out, the second time I undid the air bleed screws and poured the oil out, will any of these actions have affected the oil level level contained within the inner chamber.

 

[James]

No, the inner chamber is completely sealed and separate from the air bleed screw. That 50 mm hex simply separates the inner chamber from the outer tube but does not open the inner chamber. You have to remove the 32mm hex part from the 50mm hex part to affect oil in the inner chamber.

Glad you saw some improvement from the changes!

 

[mafrif]

If i am following this post right, since you took out 15 ml of oil from the inner shock, then added into the air bleed. They are totally seperate, so you more then likely have less then minimum oil. I to am pretty new to suspension tuning. I have the same bike. Changing the oil only affects the last half of suspension travel, actually i think the book says only the last 4 inches. So what i did was put almost the max amount of oil, 420 ml, and then set my compression to very low, only about 4 clicks in. So my initial travel is pretty soft for sharp chop, and my last 4 inches is really stiff for large jumps, i dont know if its the best, but so far i think its working pretty good, i havent been able to ride much, its been so wet here. I weigh 210 lbs, so i put new race tech springs in, they helped alot. But that bike stock is set up for a 170 lb rider , so the springs should be right for your weight.
I also just decreased my race sag to 3.5 inches, and i can finally turn my bike, before it just wanted to go straight no matter what i did, it might increase it a little more now, i have a hard time getting through the sand with my front wheel not wanting to sink.

Just a couple more thoughts

Chad

 

[James]

He removed oil from the outer chamber. The air bleed and the outer chamber are connected/the same. So if you add oil through the air bleed, it adds to the oil controlling air spring/travel/bottoming.

I tried the max oil and had compression turned all the way out like you at one time. The ride seems better to me with lower oil levels along with compression out. I control the bottoming on my MX suspension with the low speed damping on the basevalve and the heavier stock CRF450 springs (weigh 240). I run 350 ccs in this set but this is 2002 CR suspension and the upper tubes are a bit longer than the 00.

The 2000 CR suspension I have been talking about is my woods setup and it will bottom very hard if I jump certain things. Tried MXing with it Friday and regretted that choice after a few hard landings.

 

[mxcrash]

James
Thanks for confirming my thought re oil and the air bleed screw all the the pics I looked at seemed to indicate the inner chamber was sealed and oil added or removed via the air bleed screw would travel via a couple of holes just below the thread on the thread on the bronze coloured chamber.

Chad
I had my forks revalved to a two-stage stack which helped with the initial shock from short sharp bumps but the oil level has really helped, especially thru a big g-out that is quite rough, it also helps in other areas of the track where I don't have the strength (or balls) to hold the throttle open, but with this mod I have already improved my speed through some sections that troubled me

For now with the track in it's present condition, rough and whooped out, my current settings are;

fork:
raised thru the triple clamps 3mm
oil cap. 335 ml
comp. 9
rebound 12

shock:
race sag 102 mm
hs comp 2 1/4 turns
ls comp 1
rebound 5

Picked up the spanner today but as we have a big race this weekend I didn't want to change to many things we have a six week break following so plenty of time to play.

 

[mafrif]

I was planning to move up my forks just a little bit too, but the owners manual and service manual say not to. I dont know why you couldnt, but i didnt want to mess something up. On the 2001 they are suppose to be raised until the line on the forks , which are about 8 mm id guess down on the forks.

Anybody have a reason why you shouldnt raise the forks a bit on the 2000 model?

 

[James]

If you don't have enough clearance and bottom the forks, you could get tossed off. I'd measure the available fork travel with the bike on the stand and then make sure I have at least that much between the tire and the fender bolts.

The 01 has longer upper tubes to accomodate the optional 20 inch wheel. The 00 does NOT have this extra adjustability built in.

If your setup is good, it will turn fine with the forks at the standard height in the clamps.