OK, I decided on moto pro fork valves for my o9 SF. I talked to John a couple of times and it arrived in just a few days. I did not want to pull the wheel and each fork leg. I tied a 300 lb nylon tie strap around the front wheel and to the hook of my chain falls. A friend guided the bike while i picked it up until it was just hanging.

Next I took a 9/16" allan wrench over to the belt sander and made it 14mm. Next I cut 2" off the end with a 4.5" grinder and thin disc.

I used a 9/16" socket on my 1/2" drive impact and zipped the valve out with the freshly made tool. I took the valve out and followed the Moto Pro instructions carefully. I also have printed and read the chapter in the manual about suspension a couple times.


Once the valve was done, I looked in the forks to see the oil and what was going on. The part the valve screwed into was about 1" away from the end. I put another tie strap on between the wheel and handlebars. I then compressed the front suspension until the tube was where it needed to be. I coated the valve with a little grease and screwed it back in. I then snugged it up using the air wrench. Checking it often with a ratchet to see how tight it was

I been using this air wrench for 5 years daily. I do NOT recommend any one else try this. Air powered tools and aluminum threads spell disaster.

I also learned the screw we adjust for compression is a bypass. The more its open the more the fluid can go around the valve.

The new valve will flow a LOT more fluid if needed. I get all that shim stack stuff now and understand the whole setup a LOT better.

My original problem was going on rough roads at 65 mph the bike jars the crap out of me. Its high speed damping. Once I saw the original valve, I get it.

No test drive until it stops snowing.

 

Good idea about lifting the front end. Makes the job a lot quicker.

 

Congratulations for the job. I'm eager for the knowledge and understanding you have now. I think I need to get the fork internals apart too, as I can't figure out how it's configured and how it works.

A basic hydraulic damping system is just something that forces oil through an orifice when there is movement, isn't it? What's the purpose of a valve? A shim stack? Ok, I must sleep tonight so I'll try to get this out of my head for now

 

Lee Parks wrote an ENTIRE BOOK on suspensions.... To say the least I would put it as the must have read if you really want to tune a bike. Granted its for street, but same physics apply.

 

I could go on for a long time.

The old valve was kind of silly. Once I got it apart I could see why It had the harsh high speed (of the forks) compression. The compression part of the valve would not flow enough oil no matter what, It could al most lock up. The holes were too small to allow the volume of oil to flow.

Another problem I had on my bike was the front tire was deflecting when I went over the nasty set of RR tracks by where I work. Instead of absorbing the bumps the front wheel wanted to kick out to the side. IF its not fixed, I will have to take the valves out and re adjust the high speed part of the shim stack. I do think I got it though, this valve works on a different design. Only time will tell. Still snow in the road, no riding for me.

I still have the factory fork oil because The quart of fork oil I had was BMW 7.5 wt and I want 10 wt in the bike. I didn't loose a drop of what was in the bike.

The screw in the bottom is a needle and seat which will block all by pass flow when turned all the way in. As its turned out it lets more oil flow by the compression valve and the rebound valve. I blew through each one and turned the screw to make sure they worked like they should.

Understanding how it works makes it easier for me to work with it and help make decisions when adjusting.

All I need to do is test and test...

I have a new TM36-68 carb on it and these new fancy valves in the forks but Because of the snow

I CAN'T RIDE THE SONOFABITCH YET!

David

 

I will try to describe how the new valve works and I will get you a picture of the old one on monday, its at my shop (work).

The "shim stack" is a pile of flexible washers pushed up against holes around the outside of the valves. Each washer is .10 or .15 mm thick from 9 mm to 17 mm Outside Diameter.

Take a look at this picture http://www.moto-pro.com/Services.asp...ID=FORKREVALVE

The valve is the orange thing. The shim stack is on our right pressed up against the valve. When fork oil is pushed through the valve the shims resist flow but bend to let the oil go by. This is where the # and size of shim makes a difference. On the other side of the same valve is just a check valve that lets oil flow back as much as it wants so the rebound (nothing to do with the compression valve) valve can do its job.

Here is another picture of the valve with out the shim stack attached.

http://www.moto-pro.com/images/lg_UMAX3406DCK.jpg

David

 

Thinking about doing this myself.
Did you respiring it as well?
I am curious if I can change the oil level or viscosity instead of paying for a new spring. I'm 190 w/o gear btw. TNC?
Did they give you info on the oil volume.

 

I never took the forks apart or even touched the springs. That was the whole idea. Front spring on an SF is 1.1 units the S model comes with one in the .47 range. I have stiff springs. This way I only changed the valves. Had I changed the oil too I would not be sure which cured my problem. (IF its cured)

Oil volume is in the service manual posted on this web page.

Do not expect changing oil or viscosity or anything else to change the springs. The springs hold the bike up, the dampers control the springs.

I talked to John at Moto Pro about a new rear spring and lowering the bike with links. He said He would rather put a spacer in the shock than use links.

I ordered some adjustable links so I can play with the rear suspension. so far I think the rear shock is pretty good the way it is. I will get a spring once I am sure what I want.

David

 

The spring, valving, oil level and viscosity all affect how the fork performs. The oil level and it's viscosity can make it feel like there is a stiffer spring depending on the valving. The correct weight spring is important though. Has anyone tried playing with the oil?

 

Thanks a lot. Its the first time I see fork internal parts, even though I searched the net a while back for that.

There are still things I have to figure out (ex: what plays the role of piston and reservoir in this fork), but it's a good start.