Installing PD Valves

[All Things 414]

I have them (in 414). Walter put them in along with my new springs when I sent him my forks about four months ago. I think he did some adapptors as well. I haven't even pulled my forks apart since or even adjusted the valves (I was gunna but can't be fugged now). Along with my new rear shocks (YSS), I'm very happy. I couldn't be happier if I had a second willy. 

[Ji Gantor]

Hi All Things,
What bike have you got them in?
How much did YSS charge for the conversion?
How well does it work, twice as good or even better than original?

Ji

[All Things 414]

A 414 Montesa. You probably haven't heard of them. An evolution bike. I think he charged me two goats and a chicken at the time, it's all a little foggy now. Compared to my other 414 which is bog stock, it soaks up the square edged stuff a lot better. Mind you the beefier springs probably made a difference as well. I just sleep better knowing that there's a little bit of Walter in me (well, my bike).

[Ji Gantor]

Hi All Things,
Do you remember what spring rate, oil weight, PD valve size or oil level Walter used?
I am sure the other Montesa owners would love to know.

Ji

[All Things 414]

Well......the spring rate I wouldn't know but they pretty light before-hand. . The valves are for Marzoochi 38mm forks and we used 10 wgt oil. 

[Ji Gantor]

Thanks All Things,


Ji

[All Things 414]

I am sure the other Montesa owners would love to know.

There's other Montesa owners?! Bugger! I'll have to get that Carrabella now......

[brent j]

I swear by these things!

I have them in my XT500.
I'm using PE175D fork legs and they fit straight in, no mods to the damper rods. The spring spacers (hate to use the word preload) need to be shortened by the length of the valve body.

I played with oil weights and found 15 to be exellent and I'm waiting on some 20 to try.
By varying the valve spring preload and/or changing the rate of the valve spring you can alter high and low speed damping.

Changing the oil height has a marked effect as well.

It does take time to try these different settings but I think it is worth it.

I know they will drop straight in to the following forks. PE175D, IT465 (I think G) YZ250G. They will fit a lot of others without mods but that list is from my experience.

Suzuki TM125, fitting them at present. The TM has a "capped" damper rod. The cap screws on and holds the piston in place. I machined most of the cap off and made an adaptor to sit on the shortened cap. The valve sits on the adaptor. I didn't allow the adaptor to sit on the piston as it is retained on the underside by a circlip and this would take the weight of the bike.
I do plan to make a new piston to screw onto the damper rod and it will use a seal ring for better control. The new piston will accept the PD valve directly with no need for an adaptor.
I have tried to keep the overall height of the assembly as low as possible as there is limited room inside the forks with regard to length for the spring. I may yet need to machine the fork cap shorter to preserve the space for the spring. As I have mentioined earlier I don't like to preload springs.

It looks as though standard XT/TT500 forks will need an adaptor as the "C" forks I have are capped like the TM.
I'm also in the process of fitting them to 43mm forks on my other XT 500 race bike and another set of 38's.

As good as these things are I still think they should be your second stage AFTER you have the right springs.

Cheers

Brent

[Ji Gantor]

Hi Good friend from NT,
It is always a pleasure to read your words.
And what words, great advice.
The PD valve compresses the main spring which means you run more pre load, you have to shorten the spring or reduce the spacer or cap bolt by a similar amount.

Great stuff mate.

Ji

[brent j]

I do shorten springs but only to increase their rate, not for clearence.

Just a few coils off a spring can increase the rate by quite a bit.

I made a cheapskate tool for removing the valves, a piece of wire, about 3mm dia. Bend a 180 degree hook into one end so it fits around the spring on top of the valve. Then bend the hook sideways so to speak. Make the wire long enough to reach down the fork leg to the valve and then bend the other end about 90 degrees but away form the open end. This way you know which way the hook is facing when you go fishing.

I also use a mickey mouse tool for keeping the oil level static. Every time you remove the valves you lose a bit of oil. Do it a few times and you have changed the oil level enough to change the characteristics of the forks. If you are going to tune the valves you need all other variables static other wise that softer feeling could be lower oil level rather than working PD valves.
I have a piece of old brake tube, it's stuck into the end of a syringe and has a movable clamp to act as a stop. I support the bike with the front wheel off the ground and remove the fork caps. Slide the tube into the fork leg and find the oil level, lock the clamp at this point. When I rmove the spring and valve I loose some oil so on reassembly I add a bit more. I now slide the tube in and suck up any access oil so my oil level always remains constant. I use this method to set my fork oil all the time now. Each bike has it's own level and it's recorded. At a recent race meeting I had a badly leaking seal, I was able to top up the oil between races and know it was right each time.

Cheers

Brent

[Ji Gantor]

Hi Brent J,
You really are a man to respect.
Your constant vigilance on all things with springs makes me bow to your knowledge.
You are my kind of compulsive.
Keep up your experiments.

Many thanks
Ji

[brent j]

Ji I'll take compulsive as a compliment .
Usually it's names like "sad", "time waster" and such.

I think it's just that in things that interest me I'll keep trying to find that extra improvement. Rather than just have an improvement and leave it at that I want to know just how good I can get it.

And my long suffering wife will attest to that. Now if she would just let me have a play with her CRF230, I'm sure I can make it smoother..................................


As for knowledge Ji, you are the one who worked out the spring rate claculations. I just stuff around with things till they either go better or break

Brent

[mboddy]

I have posted a 'how to' on the IT Forum. With pictures!
http://www.yamahait.com.au/forum/index.php/topic,1428.0.html

[evo550]

As we all know rebound is controlled by the rebound valve and the weight of oil we use while compression is controlled by valving and the amount of oil we pour in ( the weight of oil plays no part in compression ).

Ji 
 

I thought oil weight controlled both rebound and compression action( heavier oil slower damping/lighter oil faster damping)........................or have I been barking up the wrong tree.

[brent j]

Ji's statement is correct when PD valves are fitted. With standard damper rods the oil weight does affect rebound AND compression.

Brent