Problem with shock's valve stack

[PedroMx]

Hi guys: This is a long question SORRY
I have this problem, last week I received the shock absorber (Suzuki RM 250 '93) from a guy that says he is a suspension tuner.
To make a long story short, the shock feels like a brick and I went over the bars. Hard on compression and really slow on rebound. Sick of waiting I disassembled the thing and found this :
Nut, thick washer,
rebound stack: (outside dia by thickness all in mm) 23x.25, 24x.25, 25x.05, 25x.25, 26x.25, 27x.30, 36x.10, 36x.10, 28x.25, 30x.25, 32x.30, 34x.25, 36x.15, 36x.15, 36x.20, piston,
compression stack: 10 washers 40x.10, 38x.20, 36x.25, 32x.10, 32x.10, 28x.3, and 23, 22, 20, 18x.30; thick washer
I am a little confused on this and it seems to me the stacks are wrong, the shock feels hard and the oil is Maxima Shock fluid 03w, nitro pressure is OK, bushings are OK, spring is the same that worked before, and the bike is for enduro racing.
I think that this is too much to ask, but I would like to know what is wrong. If someone of you has the info on the stock stacks or something that works I would really appreciate it.
Thanks again and sorry for the long post, you are my last hope.

Pedro :)

Pls excuse my English...

 

[shockdoc]

Are you sure the piston was in the right way? I have seen pistons get put in upside down by "suspension tuners".......... which will def. make it stiff & slow. You do show a stiff comp. stack there tho.



doc

 

[marcusgunby]

Are you sure the 10* 40mm shims are 0.1mm thick?Shockdoc did you think they were 0.2mm shims as i did when i 1st read the post i thought they were.

 

[shockdoc]

Yes, I was figuring that they were .20's instaed of .10's. I have never used any .10x40 shims. It looks to me that they are using the 2 .10x32's for a pivot with not much of a stack for H/S comp. and a very stiff 1st stage. I just shake my head wondering what people are thinking at times.....LOL :|


doc

 

[marcusgunby]

Yes i adgree that stack is wacko both on comp and rebound-it looks like the tuner just chucked the shims in the air and how they landed thats what he installed.Im afraid Pedro you need to seek out a new tuner.

 

[DEANSFASTWAY]

Yeah looks a little stiff on comp . Take out a few of those 40s or seek professional help or assistance elsewhere. Maybe something is wrong with the rebound adjuster needle sometimes they can get stuck on full hard and you will have no bypass. The needlr can also get clogged with locktite or if the guy had the lower clevis removed , the clevis could be installed (too deep) causing the needle not to move/adjust. He had to be a real numbskull to install the piston upside down so I doubt that happened. If you are skilled I would try to remove some of that compression stack and try again after checking the rebound adjuster ( to some affect the rebound adjuster affects compression by hindering flow on downstroke). If youve ever tried to bleed a shock with the adjuster needle stuck or seized youll find it almost impossible to stroke. Also the bike would have been packing real bad .Only and this is next to impossible to do but I have seen it happen , is that someone really overfilled the shock so far that it depressed/compressed the bladder to the point that there is no more compressable space in the shock and the shaft& piston wont go in . This is usuallu followed by the reservoir cap blowing off it will feel like your sitting on a brick . This last peice of motorcycle terrorism rates highest on the dumbass scale and is to be avoided at all costs because its dangerous. I saw this happen to a brand new high dollar quad shock that was built incorrectly. The remote rreservoir cap dislodged off and shot out like a cannon . GOOD LUCK DEAN

 

[PedroMx]

Thanks a lot guys for taking your time to answer.
I will use more of your knowledge if you let me.
As you see I am no expert but now I intend to become one, this thing is fascinating me.
The needle is indeed very hard to move and the cone in its tip is somewhat deformed, I thought that the o-ring on its base was too tight.
There is a checkvalve on the nut end of the rod, is operating free under compressed air but I don´t know at how much pressure it should open.
I reassembled the shock taking away 2 shims as you indicated following the directions Mr. Wilkey gave some time ago.
The rod was really hard to stroke while bleeding it and, to assure that the needle was free I disassembled the rebound adjuster and I saw the needle moving slow but free (I did not let it pass the point where it would let oil flow out). Nitrogen is set at 15 kg/cm2.
Compression worked well, tested on a 50ft double OK and on braking bumps OK, but packing is present.
Regarding the piston being upside down, this is what i see, the piston has two sets of passages one set larger than the other, I assume the larger are the compression ones. The piston has two faces in which the passages are unrestricted and also forming the base of a valve where the first shim seals the passages. It is mounted this way, the big holes will let oil pass on compression and will not on rebound (sealed by the first shim on the comp stack).
Thanks, and again excuse any butchering to the language.
I want to learn but my vacations are really short...

Pedro :)

 

[Jeremy Wilkey]

Pedro,
That is a very messed up stock stack..As noted.. Most of the stockers are there however. The 40.1's are most likely 40.15's which where stock.. That bike was werid.. Little lowspeed lots of high worked bad, but your professional jacked you up..

The 93 had the check valve type reound that does not bleed in the compression direction.. I can't recal but doc did the 93 have a 1mm bleed in the piston? I fairly sure it did..

One other ting if the piston uis in upside down its not going to seal propelry.. But sounds like that is covered..

Pedro.. I'll dig up the stock settings for you.

BR,
Jer

 

[shockdoc]

Jer
I'ts been a little while since I did a '93 but I do believe that there is no bleed hole in this piston. Could be wrong tho......

Pedro....did this shock seem hard to bleed in the normal way, like it wanted to pull the oil up instead of bleeding through the piston?

My book with all my specs from the "old days" is at home so like Jer will try to get some more info when I get a chance.

doc

 

[PedroMx]

Hi guys:

I took out two more shims from the rebound stack: 32 x.3 and 34 x.25, packing is still severe, and compression is ok for my level. Also I tried setting sag at 90mm but didn't seem to help much. Is there a way to remove the checkvalve without destroying it so it can be reassembled?

Now I am thinking of taking shims from the upper part of the reb stack but as you see I am going blind on this...

Thanks for offering to dig into your history books for the stock stack!


Thanks again, I will keep you informed of any progress.

Pedro :) :) :)

 

[marcusgunby]

Pedro most rebound stacks i see are more like this
36.2(6)
28.1
36.2
34.2
32.2
30.25
28.25
26.25
24.25
22.25
This isnt an actual stack just something like what i see, yours as you can see doesnt look anything like that-im not sure what hes done to the rebound as i havnt seen a shock internally thats older than 98, but yours sure looks bizaare.

 

[PedroMx]

Marcus:

Do you mean 6 (six) shims of 36 mm x 0.20mm?

I have eliminated all the variables I can and I will proceed to remove the checkvalve that I think is not operating normally. Do you know of someone that has tried to remove this valve?

Hope this finally works.

Pedro.:)

 

[marcusgunby]

Yes predro 6 36mm shims.I have no idea on the check valve-ive never seen one.

 

[DEANSFASTWAY]

Hey Pedro can you post a picture of what youre trying to disable? or explain it a little more in detail? Is it a stock shock piston assy or an aftermarket? Let us know . DEAN

 

[DEANSFASTWAY]

Hey Pedro how did the shock work before you sent it in ? I know this may soung illogical and in sure you probably checked it out but how is the linkage sometimes when linkages start to seize up theyll only move on the first like 1/3 of travel and seem to stick coming back. Im sure you probably checked it anyway but one time one of my customers didnt and he swore the shock was bad but after going over it and dynoing the shock he went home and greased his linkage and was much happier . Those older RMs had a lot of little individual rollers that were /are difficult to service cuz when you take it apart sometines the parts fall apartin your hands. When you stated earlier that the rebound adjuster needle was stuck and the tip was deformed did you do anything to smoothe the tip out (filing/buffing smooth) maybe its getting caught on its seat . Also if the bottom clevis is installed too deep youll never get the right range out of the adjuster, which will affect compression also. Is that what you meant by chreck valve? What spring are you using although it doesnt sound like a springing problem . Let us know . PEACE DEAN

 

[PedroMx]

Hi again:

Yes they are logical questions, before sending the shock to the tuner it was a little soft on compression (hi speed) and nothing else, I sent the thing to him because it was leaking.
The linkage is ok, everything is new (needle rollers and bushes), works fine with almost no play.
The piston is stock and I also checked the inner bleed hole and is unobstructed, spring is an Eibach that I can't recall the code but according to the White Bros catalog is correct.
I feared that if I did a touch up on the tip of the plunger it would never sit right again so i didn't touuch it.
You are right on the issue of screwing the rod too much/too little, checked the depth OK.
For check valve I mean a spring loaded ball inside a peened bush (something like the ball that holds the socket wrenches), it lets oil pass in one way and not in the other. Sorry if this is not the correct technical word for it.
But now the news, with the damn valve removed the shock is now too fast in low speed rebound...
The valve is badly deformed at both ends.
I now have the problem of replacing the valve or putting a jet on the tip of the rod.
I still have some days left for testing so we'll see.
On the funny side-if there is one-I am charging the nitrogen at the champagne factory of a friend and some wise guy said that the shock was acting weird because of the wine vapors...or he said something about WE acting weird because of...can't remember.

Thanks a lot !!!!

Pedro. :)

Mr. Jeremy did you dig into your history books?