Any shim stack readers out there?

[clw]

Changed the fork oil in a buds 2000 YZ250. Well I couldn't resist and pulled the stack apart. The rear shock wore a PA sticker, so I assume they also did the forks. It had small port pistons.
22x0.1
12x0.1
20x0.1
14x0.1
20x0.1
20x0.1
16x0.1
14x0.1
12x0.1
18x0.5 check plate
16x0.15
16x0.1
Well, is this a PA woods setup (it rides really soft compared to my "02 YZ250).

 

[mxneagle]

Yep it's a 3 stage. That by the way would be really soft if it's on the stock piston, but I suspect that it's on a PA low flow piston.

 

[clw]

This setup is too soft for the rider even with the oil level @ 95mm. It's way too soft in braking bumps and deep whoops, feels like a DRZ to me. If I moved the two crossover shims further away from the piston by one shim would that be reasonable start to firm up the stack:
22
20
12
20
14
20
16
14
12
18x0.5

 

[Jeff Howe]

Switch the 14 and 12 crossover shims around.

 

[Rcannon]

I am interested in what you rtalking about. Is there anyplace I can read up on it enough to understand? It is one of those things I would like to understand just because???? Well, I just want to!!!!

 

[marcusgunby]

Knowing the base valve setting is useful but without the midvalve setting and lift it doesnt really mean as much.If we had a stiff midvalve with very low lift that original setting would be soft.If we had a soft midvave and alot of lift(2.5mm) that setting would be super soft.

Rcannon do a search on midvalve or base valve or shim stacks, and you should find plenty of info to blow your mind for the next few days.At 1st it all seems like a foriegn language but it sinks in after a while and you will be talking to every one about bendy washers.

 

[thomasw]

22
20
20
12
20
16
14
14
12
18x0.

 

[clw]

MARCUS:
1. When you mention lift is this the free-play distance in the midvalve? or?
2. The readily apparent problem with the existing setup is what I thought was a low speed issue,ie diving and sand whoop softness. Do you need to analyze the midvalve too or can one just do the base valve shim adjustment without a lot of compromise?
thanks

 

[marcusgunby]

c/w yes i mean the free play in the midvalve-i call it lift, most call it float.

You can make adjustments without knowing the midvalve lift as you know where it feels wrong, and the base valve can be adjusted to make it better.
However to compare with anything else we need to know the midvalve settings, i make this point only as a education piece.Its always a good idea to look at the midvalve as they often have warped shims that will make the performance worse.

Do the YZs come with a 12mm clamping(last) shim std?? as thats bigger than the KYBs from a KX/CR im used to seeing.We dont have that many YZs here.
The 12mm clamp shim will increase the LSC slightly compared to the 11mm im used to seeing.

On the last shim stack posted do you think the 2 14mm shims in the HSC will be a bit much?

 

[Rcannon]

I will give it a try. I have worked on the shock of an older DR 350 so I understand that much.

I guess I just want to be able to read a bit of theory about it. What size shims do what as it were!

 

[russ17]

marcus! you stated to do a search on mid-valves, base valves,or shim stacks. do you have any sights tor books that you could recommend.

 

[russ17]

marcus! you stated to do a search on mid-valves, base valves,or shim stacks. do you have any sights or books that you could recommend.

 

[clw]

Marcus, you da man, are you a moderator here?

As to the 12 clamping shim, I just don't know. This is my first look at a Yamaha base valve, all my prior experience is with the 43 WP forks on the GG. I've been all the way down to an 8 clamping shim on them (too soft) and have settled on a 10. I was surprised what a large affect the clamping shim makes in the entire stack.

If you are asking about the stack posted by thomasw, yes my gut is that it will have too much HSC. I don't know if that's his personal stack or just his opinion on how to use the existing shims I found. His profile shows that he rides a YZ four stroke. Four strokes carry more weight on the forks and require more LSC than a 2 stroke, right? At first glance I thought the it would be too much HSC and LSC for my friends bike.

Are the 2 16's by the base plate there just for stack height? Base valve 1st, then on to mid-valves.

 

[marcusgunby]

Trust me whan i say Shocknut has loads more knowledge than me-my experience is very limited to WP43s and Bladder KYBs, Ive done a few showas but i started by working on WP PDS shocks-they were a bastism of fire-anything else seems easy.

I have found i have to make large changes to base valve shim stack strength to feel a reasonable difference.A small change to midvalve lift seems to have more effect but is more work to do.

Im guessing the extra shims are just to get the correct stack height.

Jeremy is the moderator here.

 

[marcusgunby]

Russ finding info on suspension is very hard-race tech sell a course to budding suspension builders.I have leant most from this forum-in the older threads there is a wealth of knowledge to be gained.I have just followed all the forums and read alot-its taken a long time.Also ive been very lucky when a fellow member and part time suspension tuner took me under his wing-this is very rare as suspension tuning is a very secretive world.

 

[russ17]

Marcus i just found out about this site from John from mx-tech and have stayed up nights and reading threads. I was working for a tuner but he never got into the therory aspect of suspensions I want to learn every thing I can. oh! by the way John if your on, thanks for turning me on to this sight .

 

[HONDA65]

Marcus, Just to let you know, all KYBs come with a .25 x 11 clamping shim. At least all of the newer generation stuff. So a 12 shim obviously is not stock. And I'm glad someone caught the crossovers being backward. Maybe its was designed that way, but thats not the way I would do it.

 

[John Curea]

Russ,
Its my pleasure, anytime you have some free time come on over to the shop and we'll kick around some ideas. Good seeing you at the High Point GNCC.

Take Care, John

 

[russ17]

John that would be great! I should be free here in a couple of weeks,I will definately hook up with you at the Sinclairsville Gncc and kick it around.

thanks Russ17