Tuning 04 CRF 450 forks

[moto96s]

Anyone out there feel like explaining the the differences in what part of the stroke, and the speed of the shaft(how fast the fork is compressing)the base valve and the mid valve affect. Also do their effects overlap and how? I'd also like to know how turning in or out the compression clicker affects the rebound, if at all. And how turning in or out the rebound affects the compression, also if at all.

Kelstr, have time to comment?

Thanks,

Craig

[kelstr]

well that is a good question and kinda hard to answer with my limited writing and word use skills (not to mention the lack of spelling)---but anyway-----on the clicker adjustments, they are just bleeds that let some fluid leak through the passages around the valving so you have some way of adjusting the feel and to get around too stiff or too week of valving, and in a stock preduction shock where the oil circuts are not seperated ,when you tighten up the rebound clicker and close off the bleed you are also affecting the compression because the compression was also leaking through that same passege when the shaft is going in the compression direction and you did make the compression stiffer also and may have to back off the compression adj alittle to keep the same compression feel,------now the compression on the shock does nod bleed through the shaft with its adjustment it is leaked at the upper adjuster at the resivor and it dosent affect the oil circut for the rebound----now the twin chamber preduction forks are getting very good at stoping the effect of one adj affecting the other even thoe they are not compleatly seperat circuts ,---there is some affect but slight as far as cross adjustment goes, but you still have the affect of running too much rebound and the fork is staying to low and you are feeling more compression from the stored energy in the spring because its compressed to far in the stroke-and people confuse that feel and think the rebound adj majorly changed compression,-- ---now the mid valve helps the bass valve compound its duty on damping when need be , and lets the bass work plush on its own when its not needed---like when you slam a face of a jump and that first begining fork movement is fast shaft speed, its about 25" a second of speed ----and at about 6" a second the float time is deminished and the mid comes on and adds additional damping to keep the bike up and not let it drive through and bottem and let you take off the jump kleen and it added some large lbs resistance of force ,------and it comes on on bad flat landings also and helps the same way-----now yes there is overlap from both of them being on together and it just dependes on whos ridding it,a fast hard pounding mxer will be running on the base when smoothley going through a slower corner and getting the inside rut and letting off the brakes but then he comes out and blitzes the whoops and now they are both on keeping him up and stop the wallowing, then he getts on the binders to turn rt and he getts smooth and peels in carful and it will be plush and work on the bass again,----now a slower rider that rolls the whoops will wallow because he is never enguaging the mid all the way and the bike feels loose, then he pinns it on the straight and he is the wrong body possition and to far back on the bike and the mid comes on when he hits some squair edge stuff and it feels harsh to him,and its hard to try to explain it to him whats happening and hard to valve around bad ridding habbits on a race bike. ---when you run a fork on the dyno you make a run without the mid and then you make a run with the mid and you can see where it comes in and out at and you can see the force in lbs difference-----on med shaft speed above 6" a second its comming on and by 9" its all on and up to about 5" and under its off and you are running on the base ----its kinda hard to exsplain and man my oldlady just called and she is pissed because i have been up for two days to finnish this motor for a customer that i just delevered and i cant hardly think or see any more i will read this tomorow and begin to fix it so it can be more understood ?

[moto96s]

Kelstr,

Hey, thanks alot, I'm startin' to get the idea I think. It seems like the mid valve is most active during high shaft speeds above around 6" per sec and provides additional high speed compression support to the base valve from those shaft speeds up. I do not fully understand the term "float" though. Is it the maximum amount the shim stack can deflect, or does the mid valve piston actually float on the cartridge rod? Or does it refer to the action of the clamping shim on the mid valve stack and the effect of a larger dia clamping shim as opposed to a smaller dia clamping shim? Any way I sure appreciate you taking time to respond and give me an understanding of whats going on. I hope you got some sleep by now. Next time don't worry about me till it's convenient for you. I've got plenty of time.

Thanks again,

Craig

[kelstr]

another good question, man you guys are going to force me to learn how to read and write ?-----just kidding, i realy apriciate this site for the changing of info,and the learning and leting this old man get thoughts down on paper--------anyway the float time is a space left on the shaft done with a spacer where the fluid can just blow bye and not enguage the mid damping that will kinda sets the shaft speed needed to let it bleed bye or enguage, and this space is sometimes nill (for the valve to always be on like in supercross)and or .020 to .040 of an" to very the speed from lets say 3" per second to 9" per second and most tuners mess with the float first and test with a rider to see where he needs and or dosent need the mid to come in and out at for his style and engine and chassis set up to suit him and let him gain confedense and go fast. this is kinda a simple explination of it. and on production stock suspension and some works stuff you have to change the space with a spacer,spring and compleat disasemble-----but on some of the trick new works showa stuff their is a clicker bleed with a windo of adjustament to alter the float time from nill to .030 externally and a clicker for the valving bleed to the mid valve itself, that is way kool-----that is the way to quickly see were you are at with a rider and where he likes it at ?

[moto96s]

Got it Kelstr,

Hey, thanks for the help! Little by little I'm learning. Come winter tear down I hope to apply some of this knowledge. We'll see.

Take it easy,

Craig

[BigIvyI]

great write-up ?

[moto96s]

Ok, I forgot to mention one big thing. What about the "pressure springs" and their effect on fork action? I have been told by changing to a lighter spring in this area you can make the small chop compliance better without screwing up valving that seems to work well everywhere else. Any thoughts on this.

Thanks ?

[kelstr]

well yes you can and for the guy who likes to keep his stuff fresh and dosent want to change any shims he can change the pressure spring and get a different feel ,-----especially the lighter riders,-----because in a way it makes the spring seem lighter and the valving lighter in one change and there are severial springs to run with,------now the spring is kinda like a bladder in a shock and you realy cant tune with the pressure in a shock and most tunners dont like to tune with the spring in the pressure chamber of a fork,--but it can help and is an option.