05 Honda 450 fork valving operation?

[JamesM]

I was hoping someone could offer some insite into the operation of the latest Showa fork compression valving. I have considerable experience with the forks through 2002 models but the new ones have significant changes by use of two shim circuits instead of just one as in the older versions. One controls the primary piston flow similar to the older units. The second seems to control pressure/flow peaks in clicker circuit. Both use lots of shims compared to older, smaller units. I am very interested in understanding the general operating ranges and relationship/overlap of these circuits?
In addition the midvalve has been stiffened quite a bit without increasing float. This probably relects a different intent on interaction with the new base circuits rather than just a desire to bash the rider more.
I would be happy to input the oem valving specs I found --if anyone is interested.

 

[marcusgunby]

I think you are refering to the shim stack on the bleed circuit, the idea IMO is to help hold up the fork in the stroke, IMO they overdo it as usual, i would soften the bleed stack, soften the mid but try to keep the float the same, and i would soften the passive side with a smaller clamp shim, it would then work much better for the average rider, unless you are ama expert sx?? LOL.

 

[JamesM]

Thanks for the suggestions, Marcus. These forks are used by my two son's who ride local pro level mx. Their opinion is that they are the best stock forks they have used and we are looking for small improvements. We tried a slightly softer midvalve and slightly stiffer springs (tested.47 vs.46 stock), both independently and together. I also noticed that Honda had increased spring preload by approximately 5mm to about 8mm in conjunction with reducing the spring rate for 05. Resetting this to about 3.5 mm with the .47 spring produced the plushest set up so far with no serious compromises. I consider these minor changes with minor but positive results. Testing is always time consuming and not always precise but having two bikes and identical twin riders helps alot. They do not feel the current set up needs further compression reduction and we will mull over some options for really large braking bumps and other extreme conditions.
FYI on the 02's we had some good results from increasing midvalve shim stiffness and increasing float from .25 mm to .3 mm. This seemed to allow more low/moderate speed plushness while retaining higher speed control.

 

[marcusgunby]

Its funny you mention preload, i have a set of 05 crf 250 forks and they feel like they have loads of preload-way too much IMO.

In your case i would maybe just look into softening the bleed stack a little.

 

[RVL]

I would love to know what to do with the stock valve stacks. I need it softer for choppy tracks. It is really harsh on the little sharp stuff. Can you tell me what you did to rearrange the shims front and rear to make it plusher?

 

[JamesM]

Our suspension experiements are works in progress that may not represent anything near final settings. They are, ofcourse, also subject to rider weight, application, ability, and preference. These riders are approximately 175 lbs without gear. I do not think the 05 Honda 450 forks are very far off, especially when compared to other brands and disassembly of some units from well respected prep shops. My fork suggestions at this point would start with plenty of break in and oil replacement, proper springs for your weight, and 3 to 5mm less preload. We accomplished this by using cartridge spring stops from 02 stock units. We are carefully experiementing with small shim changes and even the controversial ICS springs. ( We've had very good results in the past leaving the stiff stockers in place )
Be sure not to fall into the trap of backing compression way out and turning rebound way in.
Marcus and a few others on this site can no doubt give some good suggestions as you sort things out.