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motoman393

YZF Suspension Midvalve??

81 posts in this topic

Hey TTalkers,

This past weekend I had an accident at a local track in Splendora, TX. I broke my collar bone and I will be "out of order" for 4-6 wks. I was jumping a 140ft triple step up and was in 4th gear wide open (approx. 65 mph). After thinking long and hard about why I wrecked I have come to the conclusion that my stock suspension cant cut it for me anymore. I believe this accident could have been avoided if I would have had suspension set up for my weight/skill level! Right now my suspension is stock (still at the stock clickers and I have ATF in the forks). I weigh 168lbs w/o riding gear. ..I ride only MX and I am a fast intermediate rider.

I have read previous posts of people removing the mid valves, changing compression stacks, and replacing shims/etc. Scott F and DaveJ are very knowledgable in the suspension area and I would like to hear what you guys think! Are bottoming cones the way to go?

I know 95% of people send their suspensions to reputable shops and love the results. But I am not like 95% of the people and I enjoy working on bikes and am very mechanically inclined. I would like to "set up" my own suspension and be able to change setting from track to track. I am just picky about who sets up my bike (and I believe in the old saying, "no one cares about your bike like yourself" ) I would like to spend my hard earned money on "making my suspension work for me" and would like to keep the cost to a minimal if at all possible.

Basically what I am trying to say is: what combo do you guys recommend for me? What oil/spring rates work the best for MX applications? What should I modify internally in my forks? I read where DaveJ said, "The combo of bottom cones, ultra-adjusters, and mid-valve installed is a good one". Any comments?

I would really appreciate what you guys have to say! Because I am getting tired of wrecking due to lacking suspension! I have taken apart forks on about 20 bikes to replace seals/oil/clean etc... and have a "general" knowledge of how suspension works. And I now have alot of free time since the recent accident and would like to "set up" my suspension very soon (within 2-3 wks)! So I would really appreciate your comments! Thanks a bunch,

Garrett Berg

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Sorry to hear about her collor bone Garret. You have youth on your side so you should heal quick.

MxTuner is also very good with suspension. You may wan tot emai him.

Get Well,

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Sorry to hear about the collarbone 393. contact MXTuner at mxtuner@mindspring.com

He has set up my suspension w/ removal of midvalve. I am very happy with results. .47's,goldvalves, 95-100mm height ---still debating the cones, need more testing. DaveJ/ScottF are super knowlegable in this arena also. Get well soon.

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Ouch, sorry to hear about your crash. I have some very lumpy collarbones myself. Seems they are the easiest to break.

On your suspension, did you have the oil level up around 95-100mm? That is the first fix for bottoming but if you have the time, skill or money a revalve is best.

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Removing the midvalve will back-date your suspension 10 years....

There is a reason for the midvalve, when the first ones popped up inside 92 CRs, they werent a very good design, but they started the ball rolling.

All modern MXers use them, including works suspension...There is alot of performance to be gained by a CORRECTLY set up midvalve.

Midvalve float is just one factor upon setting up the midvalve, "float" being the distance the shim stacks travels before bottoming against the cup washer and being force to deflect which gives you the "damping".

Float distance determines at what shaft speed the midvalve will be effective. A midvalve set up with a shorter float distance will start providing damping at a lower shaft speed than one with more float.

Typically MXers like a midvalve set up with less float because it provides more bottoming resistence on jump take offs and jump landings.(which are low speed situations).

The 00 YZs had issues with thier midvalves, they actually worked pretty good for about 15-20 hours then the face shim of the midvalve stack would distort due to overflexing.

In 01, Yamaha increased the float by 1mm(which is a a huge increase) to try and remedy the problem. The float is so huge that the shaft speed has to be extremely fast before it comes into play and therefore it is basically useless.

Instead of testing and designing a new shim stack (which takes time and effort and $$)that would hold up and offer the rider better margin of suspension, some tuners just take out the midvalve shim stack (and any additional performance along with it) and try to pile all of the compression damping on the base valve.

This is another great topic......

Take Care, John

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Hey John,

I read in your profile you are an MX Tech suspension guy! I know MX Tuner is too (so I will send him an email later today).

So anyway John what would you recommend that I do? Are the bottoming cones worth the cash (I thought the 01' came w/bottoming bumpers?) What about the ATF what do you think? (there is ALOT of disagreement about this stuff?) I ONLY ride MX and am a fast intermediate rider 168lbs w/o gear! Im sure you could give me a good "starting poit" which would be more on par than right now! Like oil height, clickers, new springs, valving, etc!

For my skill and weight do I need new springs (stock is .46 and 5.4 right?) Im sure someone on this board could recommend a good starting point? Thanks for the help,

Garrett

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motoman, should have been in 5th gear. J/K, sorry to hear about the injury.. I personally send my suspension to a guy in Florida, Doug Harvey, everyone one I know who has used him, does nothing but grin from ear to ear. I would like to say I'm a good intermediate rider, weighing 210lbs, since you were trying a 140ft jump, I will assume your faster, and have bigger balls for sure. Thats a hell of a leap brother, I'll give you the specifics of my set up.

Complete revalve, much heavier spring,.

Forks:

.48 with 10mm of preload, 7w OIL@120mm. raised 12mm(much better turning). As far as clickers go, thats a personal preference. Doug runs heavy springs with very progressive damping. I don't have bottoming cones, but I hear they are pretty sweet.

Shock:

6.0 spring, again heavy springs with very progressive damping. Clickers , personal preference.

My riding time is very limited, I would like to learn how to set up my bike also, getting into the internals and all,so I prefer to have someone else do it.

I really can't say enough about his work, and ofcourse, he will work with you to get it right.

There are alot of options for suspension service, but I can tell you first hand, he does all the work.

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You ask 10 different suspension guys and you'll get 10 different answers. And, no I'm not an MX Tech advocate. I tried Jer's stuff and couldn't get it to work nearly as well as I can Gold Valves. The Race Tech stuff works way too well for me to switch to anything I've tried (and I'm continually looking for other alternatives for no other reason than to try and stay abreast of the best possible suspension.

The ATF debate is very simple. It is not a direct replacement for the stock fluid. It IS a viable alternative *IF* you revalve to compensate for the thicker fluid. If you sue it as a stock replacement, you'll give up plushness (of which I put a premium on).

The Midvalve debate. Personally I think they suck. They add another variable that, for me, creates a more difficult tuning issue. There isn't a thing in the world wrong with letting the compression adjuster do the damping alone. If John can make forks work with the midvalve, then there is absolutely nothing wrong with that. I have excellent success without them. So who is right? Both of us. Will my "midvalve" damping ever change? Nope, it can't because it ain't there.

Bottoming cones. I've never had to resort to using them. Would my set ups improve with the cones? I don't know. I've never used them. I've never had an issue I couldn't resolve without them.

Spring rates. I prefer to use the softest springs I can to give the desired results. This means the 170 lb rider isn't going to need to go to the .47's all the mags recommend. Stiffer springs prevent the front end dropping in a corner. This isn't good for cornering. The front end *needs* to drop to promote good corner carving.

I know this doesn't give you the specific answers you wanted. Basically you need to ask one person and try their set up. You start mixing different set ups and you can get a miserable handling bie that doesn't supend well at all.

I have way too many customers who will ask 5 different guys around here (most of THEM being parts caunter guys -generally the clueless variety) and believe the person who gives the the answer they want to believe, for whatever reason, instead of who they should believe. This falls into the category of tying to convince someone I know what I'm doing.... which I won't do.

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Hey MX Tuner,

Thanks for a honest opinion! I appreciate it! So you think I need softer rate springs?

Garrett

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Motoman,

Sorry to hear about the collarbone. Get well soon.

Regarding, the YZ's mid-valve, I am currently riding an '01 YZ-250 (and have had several YZ250's over the past 2 decades). I know, I know, this is a 4-stroke forum, and the reason I partake is that at 36 I am seriously considering a '02 YZ-426F!

Back to the suspension question. I have had good luck w/both my '00 & '01 YZ-250 by having my local Race-Tech guy change out the mid-valve and replacing it w/a check style valve. Using the correct springs (.46) and a 95mm oil level this has worked great for my VET intermediate, (6'3", 220lbs) ability. Basically, I have gone this route as a cheaper alternative to Gold Valves (which I used w/great success in my '97 & '98 YZ's) Using the check valve is by no means a step back as someone posted above. Paul Thede the Race Tech guru has this suggested for all YZ forks! The stock mid-valve is overengineered and is very easy to blow through if you are fast or over 200lbs. If you couple this w/the Gold Valve or even better, the Delta Valve you will have sweet working forks.

Just my .02c

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Hey Motoman,

I'm in kind of the same boat as you. My suspension works volumes better than the 00 250 I got off of but it's still way too stiff. I've been going through the dilema of how to do my suspension. If you want to do it yourself, it has been recommended to me by several to go with Race Tech. To my knowledge they will send you a video and good support if you want to do it yourself. (I haven't personally tried them, only feedback I got.) I was going this route but I have a friend who's dad is a Pro Action dealer out of Wis. and he is giving me a break on cost and setting it up for me about as cheap as i can purchase the Race Tech stuff.

As for the oil, I just drained my stock oil and it was clumpy after 3 weeks of riding. It was about like old motor oil with 50k miles on it. I'm going with the Race Tech oil and it really softened my front end up and made it work a lot better. (Springs are still too stiff however.) I have been warned to stay away from some oils like silkolene in the Kayaba forks. I have first hand experience how the oil gets real inconsistent when the forks heat up. They recommended going with the Kayaba fork oil. They told me if I didn't believe the other oils were bad, measure the sag on the front when the bike was cold. Go out and ride it for a while and remeasure.

As for spring rate, you can find it in a lot of readings on the internet. For the front, I believe the sag should be between 15 and 40 mm (Not sure of exact but there abouts.) For the rear, set your race sage between 90 and 105 mm and then check your static sag. If it's less than 15 mm, the spring is too soft. If it's more than 25 then your spring is too stiff. (Sounds backwards but it's right.)

Good luck!

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Science,

Thanks for the tips I will take them into consideration when I purchase new stuff for my forks! Hopefully we will see you soon with a 02' YZ426 (you will never go back to 2 smoke again LOL)!!

<hr>

MX Tuner,

Right now I am at stock springs and stock clicker settings on a 01' YZ426 the only difference in my bike is I have Mobil 1 Syn. ATF in the front forks and the recommended standard oil height which I think is 130mm. I have plugged my weight into about 3 charts and they all point at .44 for the front forks! If I change out my front springs Im sure it would make my bike fell unbalanced right? So I would have to goto like a 5.0 in the rear? Please let me know what you think and tell me if I am "off course" here...I am just a newbie at suspension so thanks for bearing with me (the only thing I have done suspension wise is change fork seals and I have done like 20 of them)! I one day hope to learn suspension well, and be able to apply my knowledge and help others! Thanks a bunch,

Garrett

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You should be fine with the stock springs. Just don't go with any more preload. Don't add any spacers. Technically you should go with softer springs. Will it be cost effective? I doubt it. Would you notice softer springs? Yes. Would it make you any faster/decrese your lap times? I truly doubt it.

Personally, I'd lose the ATF, use 5wt Bel-Ray HV-1 susp fluid and run it at about 95mm. Back the compression clickers out until it begins to bottom slightly. This is about as good as you can do with stock forks.

The biggest disadvantage with sending your stuff to Pro-Action (or most other shops) is the fact if you don't like it, you have to send it back to them. With Gold Valves (installed by yourself) you can go in and swap shims in about an hour. Besides, I can beat any of Pro-Actions forks hands down in plushness and bottoming resistance without harshness with Gold Valves. I guess you can tell I've never been positively impressed with any of PA's work.

Garrett, if you want to do the Gold Valves, I'll give you a valve stack recommendation. I wouldn't use RT's stack. It'll be too harsh. I can answer any questions you have better than RT's dorks can. Don't expect a quality answer from the guy on the other end of the phone. Seems doing bong hits is a part of a good breakfast out there. And DON'T even think about the Delta Valves. Way too much trouble to get right. And once you do, don't touch the adjusters or you'll end up starting from scratch.

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MX Tuner,

I really appreciate your quick response!!

Thanks for the tip about the ATF...I will give the 5wt Bel-Ray HV-1 a try!

I know a few people (from the track) who hated there suspension more after they sent it to a shop for a revalve (and the shops are out of state :) )...just like you where saying! That is why I would like to learn how to do this myself. I can split cases/top ends, etc, and do any engine work...but I havent learned suspension yet!

About the Gold Valves...I installed Gold Valves on 1 of my previous bikes (and another set on a friends bike) and they were great (it gave you much more adjustibility and plushness)! I never swapped shims on a gold valve (but it didnt look hard, just take the nut off and restack am I correct?)

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:<HR>Garrett, if you want to do the Gold Valves, I'll give you a valve stack recommendation. I wouldn't use RT's stack. It'll be too harsh. I can answer any questions you have better than RT's dorks can. Don't expect a quality answer from the guy on the other end of the phone. Seems doing bong hits is a part of a good breakfast out there. And DON'T even think about the Delta Valves. Way too much trouble to get right. And once you do, don't touch the adjusters or you'll end up starting from scratch.

Yeah, I would appreciate if you could give me a valve stack recommendation for the Gold valves!! I was planning on ordering them next week and this was the "push" I needed! I never have used the delta valve (and I wont ever use it now LOL)! Yeah I knew RT's guys dont know which end is up, I called up there about a yr ago and asked what fork oil they recommend...of course it was the $60 a qt. bottle! LOL Well anyway I really appreciate your help. Hopefully I will know enough when I get through with my suspension to help others with the same problem! Thanks,

Garrett Berg (motoman393@hotmail.com)

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Motoman,

Sorry to hear about the miss hap, and hope you're healing well.

Not sure what the details of your jump were, but I'll have to assume you cased it. Which means mid-valve or not, or bottoming cones, you most likely would have ended up in the same condition.

Going forward, for your level of riding, I think I would leave the mid-valve in.

I only recommend its removal for trail or technical riders that find the YZ factory setup too harsh on high compression movements.

However, bottoming cones are a nice addition, but do little for the majority of suspension usage.

As for valving, I think the factory unit is hard to beat, (however, Race Tech stuff does work and the convenience of their valving stack sheets can make it easier for those with less experience).

Perhaps you should share what you don't like about your ride and what your expectations are for future performance, (and the details of what went wrong with your jump). Then perhaps we can narrow down on some recommendations.

DaveJ

[ November 05, 2001: Message edited by: DaveJ ]

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Dave,

From what I am told (I was knocked unconscous and dont remember a thing about the wreck) I had been clearing it all day long just fine. But the time I wrecked my bike started to get headshake on the straight away before the jump and I continued to "pin in" in order to clear the jump. Well in the air my bike was nose high and I landed like that (on the rear wheel ) and the force from going 65mph slapped my front end down and this is what caused my wreck (keep in mind it is a step up and it normally is a smooth landing jump)! I went over the handlebars and tucked and rolled and this is what broke my collarbone!

The reason I know my suspension isnt the greatest is: I was riding with 2 guys at the track (one was on a CR450 and the other on a YZ426) They were easily pinned out on straight aways (with no headshake) While I was struggling to keep my front end from swapping back and forth! Thanks for your help,

Garrett

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Motoman

Lets get back to the basics:

1. Get the correct springs, YES, they are important. Headshake is a direct result of your bike being unbalanced. Due this before spending any money on any valving.

5.2 shock .44 fork

2. As far as bottoming cones go, let that be the last item on your list....reason being is that the stock bottoming bumpers due a pretty good job. The stock bumpers are of a "closed cell" design, Yamaha was working with "open cell" bumpers, that of like on your shock. The open cell design had superior bottoming properties but they were deteriorating in the fork fluid, causing contamination. They went with the closed cell (like a pencil eracer), they gave up some bottoming resistance, but the the material doesnt break down.

3. Do a complete teardown and inspection. (there is a procedure I posted somewhere around this site, let me know if you cant find it) replace any worn components. I guarentee the face shim on the midvalve (active valving)will be distorted. No problem, you can buy replacement shims from any major suspension dealer.

It is very important that you do a very thorough inspection, only way is to COMPLETELY teardown the components, I am talking complete disassembly of the base (passive)valving and midvalve (active) compression and rebound shim stacks.

Also check to make sure that the stock stacks are correct. I have seen stock rebound stacks built incorrectly from the factory. The best way is to get the actual stock stack build that the fork was designed with, the new MX-TECH website(should be up late monday) will have most of the late model bikes build info. The quick way is to lay out both stacks from each fork leg and compare, if they both are the same, you might be ok. Do this check on all valving.

4. Use a quality suspension fluid, Belray or Mobil 1 ATF. I havent heard any arguement here worth anything (except unsupported speculation )why ATF wont work.

5. I would set the fluid height at 90mm for good bottoming resistence. Fluid height only impacts the 2 to 3 inches of travel.

Good Luck, John

BTW...Cool website 393!!

[ November 05, 2001: Message edited by: John Curea ]

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Garrett, sorry about your crash...that triple at Splendora is a Monster, though....I was lucky to clear the second step!

Hope you get ridin soon...was nice to meet you and your Dad at Motoplex 2 weeks ago.

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DaveJ

The only problem with installing bottoming cones is that you will be increasing damping in the worst area- the high speed circuit. You have to understand that the cylinder valve (what you call seal head) has a shim stack inside that is very linear in design. It doesnt flow oil until you have a high speed hit, then it blows off, softening the hit.

When you replace this cylinder valve with a bottoming cone (which does not have a high speed circuit)you increase the high speed damping (spelled harsh)because you just removed the high speed damping of the CV. In order for the bottoming cones to work well YOU MUST soften up the high speed circuit on the base valve to compensate. They are not just a direct replacement for the cylinder valve, there is much more to it.

Yamaha has actually changed the high speed circuit in the '01 426 cylinder valve, can you guess which direction they went?

Dont get me wrong, bottoming cones work really well in certain circumstances, BIG hits , missed timed jumps, flat landings etc. . 90% of the time the elastometer(bottoming bumpers)works much better. On a slow speed bottom, bottoming cones offer almost no resistence(spelled damping). The shaft speed has to be pretty fast in order for them to work. If you think about it, if the shaft speed is too slow through the bottoming cone, it will easily displace the oil in the lock providing little or no damping.

The main office of MX-TECH has done alot of research with the engineers at Mobil before they ever tried this fluid. We blend this with a velacite product to lower the overall weight a little. But as we stated somewhere else on TT that fluid viscosity directly affects LOW speed performance, the additional low speed damping that this fluid produces(which would actually be a plus in motomans huge air jumps)can be tuned out with the clickers. The clickers as we all know primarily affect low speed performance.

No reason to contact KYB on this matter, we already have a huge amount of testing with positive results and very satisfied customers.....

As far as the headshake goes, we basically have two types, gas off deceleration headshake and gas on high speed head shake. When motoman is blazing at 65mph and his front end starts shaking it is usually because the front end is too stiff. When the front tend is too stiff it is easier for the front end to displace the rotaional mass of the spinning front wheel to the side than it is for the suspension to absorb the hit. This is a direct result from him using too stiff springs for his weight.

Just for thought- Decelleration headshake is usually because the front end is too soft and the front goes too far into the stroke, sigificantly tightening up the bikes geometry.

As far as spring rates, going to the factory teams might just suprise you. Pastrana was running a progressive fork spring starting at a .34 rate !! If I put that in a customers bike, he would probably launch it right back at me !!

The factory riders have some pretty wild set ups, have you ever noticed how soft RCs shock is, it seems to flatten out on the smallest stuff on the course. His forks are rumored to be very stiff. I dont really see how taking those spring rates and applying them to the average rider would do any good.

I think you might have gotten motomans weight (168#) mixed up with someone else posting on this thread, there have been a few different readers posting there weight.

Even if motoman was running pro level SX, I wouldnt put him on anything stiffer than a 4.6 in the fork.

I hope this helps

John

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