Highspeed or low speed rebound on DR650

[atpalmer]

I have a DR650 with upgraded rear spring and Racetech gold valve. Racetech has a shim stack table with recommended stacks rated from 1(soft) to 20 (stiff). I am currently set up with CL3, CH2, RL5, RH3.

When I ride over 3-4' or small jumps the rear end will buck a lot. I know that I need more rebound damping but I am unsure if I should stiffen the high or low speed rebound shim stack. Since I have to rebuild the shock for everry adjustment I don't want too many trial and error rebuilds. Any advice?

[Xfool]

For a DR650 on a four foot jump I would think you are going to need a boat load more compression damping.

But since you bought your suspension valves from Race-Tech didn't they tell you how to set it up?

[Bushmechanic]

stiffer HS section in the reb stack should help with that

but yes stiffer comp could also help, that is one way to look at it. if the wheel doesn't go in it doesn't come out

but bottom line is the HS rebound needs to be stiff enough to control the extending wheel from full bottoming which will happen sometimes unless the bike is just too stiff

[atpalmer]

You can see the suspension issue in the hillclimb at 1:03 in this video.

[atpalmer]

stiffer HS section in the reb stack should help with that

but yes stiffer comp could also help, that is one way to look at it. if the wheel doesn't go in it doesn't come out

but bottom line is the HS rebound needs to be stiff enough to control the extending wheel from full bottoming which will happen sometimes unless the bike is just too stiff

Okay, so HS reb will help with the over extension in a jump. what circumstance would require a LS reb adjsutment?

[Bushmechanic]

HS reb stiffer helps control extension after bottoming sometimes you bottom out on the jump face so yes. though as said before you could also make the compression stiffer so it doesn't bottom as much

LS reb softer helps reduce packing over small bumps, too soft and the bike will sort of wallow upwards in slow rocking chassis movements. a teeny bit too stiff and you loose traction, bit stiffer still and its harsh on repeated small bumps

[atpalmer]

thanks Bush. Looks like i'll try a couple steps stiffer on the HS Reb. Now I just need to find a day to rebuild.

[Bill Hamilton]

On 10/24/2010 at 3:44 AM, atpalmer said:

thanks Bush. Looks like i'll try a couple steps stiffer on the HS Reb. Now I just need to find a day to rebuild.

Once you get the shock rod out of the case how are you holding it to get the end nut off?... I'm in the process of dismantling my shock now.

[DEATH_INC.]

3 hours ago, Bill Hamilton said:

Once you get the shock rod out of the case how are you holding it to get the end nut off?... I'm in the process of dismantling my shock now.

The nut that holds the piston on? I just put the bottom mount/clevis in the vice with some soft jaws. The piston nut will be peened or the top of the rod rolled over it, so you need to carefully file that off. Do a search, it'll come up. This pic shows what I'm talking about, though I don't file it this far;

Other wise you'll need a shaft holder, basically a piece of soft metal (ally usually) with a hole bored through it the size of the shaft and a slot to allow it to clamp in a vice and hold it without damaging it.

Edited March 8, 2021 by DEATH_INC.

[Bill Hamilton]

1 hour ago, DEATH_INC. said:

The nut that holds the piston on? I just put the bottom mount/clevis in the vice with some soft jaws. The piston nut will be peened or the top of the rod rolled over it, so you need to carefully file that off. Do a search, it'll come up. This pic shows what I'm talking about, though I don't file it this far;

Other wise you'll need a shaft holder, basically a piece of soft metal (ally usually) with a hole bored through it the size of the shaft and a slot to allow it to clamp in a vice and hold it without damaging it.

Thanks for the quick comment.....  Yeah I just got 2 nuts with the appropriate 1.25 thread pitch cut a slot in them put them on the lower threaded rod and installed in a vise. used my impact gun to take the nut off. Very easy. Now all I have to do is find the cash (I'm frugal) for one of those lovely gold valves and shims and It'll take no time to get the shock back together.  

Capt. Billy.

[Bill Hamilton]

I notice you just added shims to the existing piston (valve). or am I mistaken there. Is there a rebuild kit for these shocks, which includes seals and 

O rings etc?

[atpalmer]

I finally resolved the rear shock bucking problem. It took 11 years to save up $$ and buy a Beta 390.?

[DEATH_INC.]

4 hours ago, Bill Hamilton said:

I notice you just added shims to the existing piston (valve). or am I mistaken there. Is there a rebuild kit for these shocks, which includes seals and 

O rings etc?

You can normally find a complete seal head from various manufacturers. Racetech should have all the separate parts if you want to go that way.

https://racetech.com/index.aspx

Fwiw, most shock pistons actually do a decent job. A re-valve should give you what you want without needing the Goldvalve.

[Bill Hamilton]

One can buy shims separately. I just wonder if the stack would function better with a different stack. (I know nothing)

[DEATH_INC.]

4 hours ago, Bill Hamilton said:

One can buy shims separately. I just wonder if the stack would function better with a different stack. (I know nothing)

He doesn't go into much detail. The stock piston needs a different stack to the GV. This is really the big advantage of purchasing one, it comes with all the shims you need, and a valve stack that should work well for you. It's not a bad idea if you haven't done this before.

Another option will be to search around the forums and try to find a starting point from someone elses stacks.

Otherwise if you know what you want it to do better, post up your current /stock stack and what needs improving and we'll give you some ideas to try.

Edited March 10, 2021 by DEATH_INC.

[Bill Hamilton]

16 minutes ago, DEATH_INC. said:

He doesn't go into much detail. The stock piston needs a different stack to the GV. This is really the big advantage of purchasing one, it comes with all the shims you need, and a valve stack that should work well for you. It's not a bad idea if you haven't done this before.

Another option will be to search around the forums and try to find a starting point from someone elses stacks.

Otherwise if you know what you want it to do better, post up your current /stock stack and what needs improving and we'll give you some ideas to try.

Well of course This is the stock setup and I know I want something better but I'm not sure how to accomplish this.  I'll keep looking and asking. Spring is on its way but there is still snow on the ground and I have other projects to wade through yet. Time is on my side but it would be nice to know what direction to go most economically. 

 

[Bill Hamilton]

On 3/9/2021 at 1:23 AM, DEATH_INC. said:

You can normally find a complete seal head from various manufacturers. Racetech should have all the separate parts if you want to go that way.

https://racetech.com/index.aspx

Fwiw, most shock pistons actually do a decent job. A re-valve should give you what you want without needing the Goldvalve.

Re-valve?   Having taken it apart.... It's just a hunk of metal with fancy holes. I can knock one out in my machine shop. 

[DEATH_INC.]

56 minutes ago, Bill Hamilton said:

Re-valve?   Having taken it apart.... It's just a hunk of metal with fancy holes. I can knock one out in my machine shop. 

Yes they are just a round bit of metal with some holes, guys have made their own before. The gold valve is just a round bronze (gold) bit of metal with fancier holes.

Re-valving actually refers to changing the shims around to change the damping.

Edited March 12, 2021 by DEATH_INC.

[Bill Hamilton]

In think the problem is getting the specs to stack the shims to allow the piston to do what you want it to do. 

Shims are $19.

[DEATH_INC.]

2 hours ago, Bill Hamilton said:

In think the problem is getting the specs to stack the shims to allow the piston to do what you want it to do. 

Shims are $19.

There's sometimes different ways of doing it. If you just want to stiffen it a bit, you can take the smallest 'pivot' shim out and let it pivot on the next biggest one.

So for example if your shim stack has say 10 big shims against the piston, then 1 or 2 smaller ones, then a big one again, then it tapers down to a small (around 20mm or so) one.

Listed like; the first number being the diameter in mm, the second the thickness in points of a mm, so 38mm diameter x 0.1mm thick becomes 38.1. The ten in brackets indicates there's 10 of them. Start from the piston;

38.1 (10)

34.1

28.1

38.1

36.1

34.1

32.1

30.1

28.1

26.1

24.1

22.1

20.1

then the washer, though sometimes there will be a couple of bigger shims here too, before the washer.

So, you can remove the 20.1 and leave the smallest as the 22.1 and it'll make it stiffer.

This is just an example to give you the idea, yours will be different. If you want to measure and list yours it may help for us to offer suggestions.

 

Edited March 13, 2021 by DEATH_INC.