yz fork and shock interchange

[MrN2OBelvedere]

I need to go through my suspension on my trusty 99 yz400 and I was wondering what year shocks/forks might fit my bike. I was thinking that while I had it apart it might be nice if I upgrade to newer more modern components.

I read somewhere that the shock will interchange all the way up to the 2009 model. I am not sure about what forks might swap out. If anybody knows the answer to this I would greatly appreciate it. Thanks!

[grayracer513]

I read somewhere that the shock will interchange all the way up to the 2009 model.

That's true. There are some minor differences in length, but they work.

Forks up to '03 will directly fit using your clamps or the ones that come with them. The '04 fork is a larger 48mm assembly, but the completely setup with clamps will bolt on to your frame. Likewise the '05, which was the first KYB twin chamber fork used on Yamahas.

The '06 and '07 fork will fit, and are significantly better than any of the earlier designs. You need to use the '06/7 clamps though. Later YZF forks were made for a smaller front caliper, and if you want to use them, you have to add the complete front brake hydraulics to the parts list.

[2grimjim]

That's true. There are some minor differences in length, but they work.

Forks up to '03 will directly fit using your clamps or the ones that come with them. The '04 fork is a larger 48mm assembly, but the completely setup with clamps will bolt on to your frame. Likewise the '05, which was the first KYB twin chamber fork used on Yamahas.

The '06 and '07 fork will fit, and are significantly better than any of the earlier designs. You need to use the '06/7 clamps though. Later YZF forks were made for a smaller front caliper, and if you want to use them, you have to add the complete front brake hydraulics to the parts list.

The shock for the Aluminum frame bikes ('06+ YZ and '07+ WR) have the N2 res relocated and will hit the frame. The only ones that will work are from any of the steel frame bikes.

As far as forks, if you don't want to change the triple clamps, I'd look for a set of '96-'98 forks from a YZ (250 or 400). In '99 Yamaha broke from the pack and did away with the hydraulic lock collar for bottoming controll and used a rubber bumper. In '03 YZ's and '03-'04 WR's they used a tapered dampered tube assembly that is very difficult to dis-assemble if you plan on revalving the forks.

[grayracer513]

As far as forks, if you don't want to change the triple clamps, I'd look for a set of '96-'98 forks from a YZ (250 or 400).

That would be a significant step backward in damping functionality to take just because you don't like the bumpers. Personally, I fail to see how bothering with any open bath YZ fork is a pursuit worth the effort or expense. Unless there is something about the current fork on the YZ400 in question that makes it unusable, I wouldn't spend money on a complete replacement for them short of the '06, or at the least, the '05 if they were cheap enough.

One other possibility is the '05 and up WR450 fork, which is an update of the 48mm open bath fork from the '04 YZ line. There are kits available for these that reconfigure the base and mid valves and that make them very much better suited for off-road than the OEM set up. Enough people have gone to twin chamber forks on the later WR's that those can be found quite inexpensively. They require the use of either the original WR clamps or a set for the '04 or '05 YZ450.

[2grimjim]

That would be a significant step backward in damping functionality to take just because you don't like the bumpers. Personally, I fail to see how bothering with any open bath YZ fork is a pursuit worth the effort or expense. Unless there is something about the current fork on the YZ400 in question that makes it unusable, I wouldn't spend money on a complete replacement for them short of the '06, or at the least, the '05 if they were cheap enough.

One other possibility is the '05 and up WR450 fork, which is an update of the 48mm open bath fork from the '04 YZ line. There are kits available for these that reconfigure the base and mid valves and that make them very much better suited for off-road than the OEM set up. Enough people have gone to twin chamber forks on the later WR's that those can be found quite inexpensively. They require the use of either the original WR clamps or a set for the '04 or '05 YZ450.

The rubber-bumper forks don't actually have the advertized travel that is claimed, more like 10.8" instead of 11.8" because of the physical barrier of the bumper.

The '96-'98 forks are virtually identical to all of the 46mm forks used up to '04 save for the bottoming system. They are also really cheap if you you go to buy a used set.

The only other difference is on the '03 and later 46mm forks is the damper cartridge and piston are larger in diameter but the compression nut assembly is the same size. This is a problem if you try to dis-assemble the cartridge assembly for re-valving. Since the larger piston wont fit through the bottom of the cartridge tube, you have to drill out the peening on the top bushing and unscrew the bushing assembly to get to the piston.

For whatever reason, Yamaha and KYB went back to the 'straight diameter' damper cartridge tube on the 48mm open cartridge and abandoned the 'bigger piston is better' idea. So the 'new technology' 48mm open cartridge forks are internally identical to the 'old school' '96-'98 forks...just with stanchion tubes 2mm bigger.

[grayracer513]

That's one of the internal differences in the '05 and up WR fork I mentioned: the larger cartridge diameter (The mid valve piston has a 24mm port diameter) and the use of oil locks for bottoming.

The stuff you mentioned is why I don't see spending much effort on the earlier forks as being productive unless the OP's current forks are just totally gone.

[2grimjim]

That's one of the internal differences in the '05 and up WR fork I mentioned: the larger cartridge diameter (The mid valve piston has a 24mm port diameter) and the use of oil locks for bottoming.

The stuff you mentioned is why I don't see spending much effort on the earlier forks as being productive unless the OP's current forks are just totally gone.

For $150 he can get an inch of fork travel. Sounds like a bargain to me.

If he's going to get the 48's he will have to replace the clamps too.

The oil-lock, open cartridge 46mm forks can be made to work quite good. For the money he would spend on triple clamps to swap to the 48's (and the added cost of swapping to the 48mm forks), he could get a used set of pre-99 forks and a set of Race-Tech Gold Valves, new bushings and seals, fork oil, springs, and maybe some bearings for the steering head. Still a bargain.

[grayracer513]

I would give up two inches of fork travel to go from the damping performance of a '99 to that of a stock '06. That last inch of travel is way overrated. Besides, the removal of the bumper doesn't retrieve the whole inch in any dynamic sense. Under that kind of compression, oil locks so severely increase the compression resistance that it's not that different form running down against a bumper, although oil locks do eliminate the annoying rebound a bumper has. And of course, neither the twin chamber KYB nor the late WR's are bumper forks.

[2grimjim]

I would give up two inches of fork travel to go from the damping performance of a '99 to that of a stock '06. That last inch of travel is way overrated. Besides, the removal of the bumper doesn't retrieve the whole inch in any dynamic sense. Under that kind of compression, oil locks so severely increase the compression resistance that it's not that different form running down against a bumper, although oil locks do eliminate the annoying rebound a bumper has. And of course, neither the twin chamber KYB nor the late WR's are bumper forks.

Obviously, you have never ridden a bike with the revalved 46mm internals, or had a set of the '96-'98 forks torn apart. Because if you did, you wouldn't make such a silly statement.

You are missing my point completely. The gentleman has a 1999 YZ400 wanting to make some improvements. I can't imagine he spent more than $1500 on this bike (at least I wouldn't). Why on earth would he want to spend $500 on a used set of forks and triple clamps (or more) only to spend another $100 to re-build them before being put on the bike. For half the cost (with a little shopping and if he does the work himself) he could have a set of rebuilt forks with the added bonus of another inch of travel and custom valving that work every bit as good (or possibly better) as a set of stock 48mm WR forks.

Edited December 20, 2011 by 2grimjim

[2grimjim]

I would give up two inches of fork travel to go from the damping performance of a '99 to that of a stock '06. That last inch of travel is way overrated. Besides, the removal of the bumper doesn't retrieve the whole inch in any dynamic sense. Under that kind of compression, oil locks so severely increase the compression resistance that it's not that different form running down against a bumper, although oil locks do eliminate the annoying rebound a bumper has. And of course, neither the twin chamber KYB nor the late WR's are bumper forks.

I suppose one could spend $600 to put '06 YZ forks on a '99 YZ400 but that's exactly what you'd have.....a '99 YZ400 with '06 YZ forks. Not quite the same as a '06 YZ450.

[2grimjim]

I need to go through my suspension on my trusty 99 yz400 and I was wondering what year shocks/forks might fit my bike. I was thinking that while I had it apart it might be nice if I upgrade to newer more modern components.

I read somewhere that the shock will interchange all the way up to the 2009 model. I am not sure about what forks might swap out. If anybody knows the answer to this I would greatly appreciate it. Thanks!

Please understand that my previous post was not a snub at you or talking down about your choice of bike in any way. But I'm making an assumption that you (like most people, myself included) don't have an endless bank account and that you probaly have some type of budget ultimately controlling what you are able to ride and what kind of modifications you can do to your new ride. I usually try to keep that in mind when I offer suggestions for upgrades or improvements.

Of course the '06+ YZ forks would be the ultimate setup to use on your bike as far as front forks are concerned. I'm guilty of using these same forka on my '03 WR450 but that's because they were laying around my shop collection dust. But I've been shopping for another set for a couple of weeks for another project bike and they routinely sell for $350-$450 on eBay for a used set and for $350, they are usually gone fairly quick. You'll have to get of triple clamps to match for an additional $100-$200. Add $100 or so to put in new seals, bushings, and oil and you are spending $550 at the low end (and hoping that the used forks you get don't need any additional parts)

The '96-'98 46mm forks can be had for as cheap as $75. Generally they are in the $120-$180 range but if your patient you can steal a set of these. Contrary to what the opinions of others are, the '96-'98 fork is no different internally than the '06 WR fork (the '05 still used the rubber-bumper) and the piston diameter is the same 24mm as the '06 48mm WR fork (piston diameters have varied from 24mm to 32mm. The 32mm piston being used on forks from '03-'05).

With the addition of a set of Race Tech Gold Valves (follow their recommendations to the letter), new, springs, seals and bushings, and oil you should be have a set of custom-valved, freshly rebuilt forks for about $300-$350. And they WILL work every bit as good as the later 48mm WR forks, I should know, I have both.

Another advantage of sticking with the early style forks vs. the '05+ YZ forks is how easily they can be serviced. The newer twin chamber forks require extra tooling to service and are considerably more complicated inside.

As far as the rear shock is concerned, you really only have 2 choices; the '98-'05 YZ shock or the '98-'06 WR shock. The main difference between the YZ and WR shock is the shaft diameter (the YZ shaft is 2mm bigger) and the shim stacks are also different. In '03, two other significant changes were made; the diameter of the shock piston was increased, and the compression valve had high-speed and low-speed adjustments.

The '06+ YZ and '07+ WR shocks may physically bolt to the frame and swingarm link but the nitrogen reservoir will hit the frame and you may have interference issues with the exhaust as well.

Used shocks can be had for around $100-$150. I think the preferred one would be from an '03-'06 WR450 or a '03-'05 YZ450. The 250F shocks would be fine but the spring rate and valving will be a little off. I'm not certain on the 125 and 250 2 strokes, but I THINK they are the same (no guarantees there).

[grayracer513]

Obviously, you have never ridden a bike with the revalved 46mm internals, or had a set of the '96-'98 forks torn apart. Because if you did, you wouldn't make such a silly statement.

There's nothing at all silly about it. I have indeed ridden several sets of revalved 46mm KYB's including my own, and some by Factory Connection, Pro Circuit, and a set by Enzo that cost $1800 for the work in 2002. None of them were close to what I have now, which I did for about $300.

Sorry.

[2grimjim]

There's nothing at all silly about it. I have indeed ridden several sets of revalved 46mm KYB's including my own, and some by Factory Connection, Pro Circuit, and a set by Enzo that cost $1800 for the work in 2002. None of them were close to what I have now, which I did for about $300.

Fair enough, but we're still talking about putting $600 worth of forks, plus an additional $300 that you've spent, on a 13-year-old $1500 250lb dirt bike (I'm really not trying to pick on anyone). I'm talking Economics 101.

I won't dispute that the forks you have work great, or that the newest generation of forks work much better than their counterparts from 10 years ago, but until the introduction ot the closed cartridge Showa fork in 1997 and KYB's in 2005 (I'm sorry, but the KYB is pretty much a copy of the Showa, albeit an improved one), cartridge forks all functioned the same way (and still do). I'm not trying to compare open cartridge vs. closed cartridge forks. Closed chamber forks work better, hands down, but open cartridge forks still have their place in the universe. Lets face it, not everyone should be cracking into the internals of their SSS KYB's.

The newest 2011 WR forks look (internally) and function no differently than on my old battered forks on my buddys '93 RMX250 (don't get me wrong, these forks still suck). My wife has them on her '07 WR250 and they worked great right out of he crate. Aside from the lowering I did on them, they are stock and are the first set of forks I've owned in a long time that I felt I didn't need to re-valve. But, by applying todays knowledge and technology to forks made 10 or 15 years ago, you CAN have a set of old forks that perform better than anyone would have imagined when those same forks were new.

Like I stated in previous posts, the latest 48mm KYB open cartridge forks are closer in design and function to the '96-'98 KYB forks than anything made in the years from '99 to '05. This tells me one thing: the old design wasn't that bad in the first place. And for 2/3rd's of the riders out there, they wouldn't be able to tell the difference anyway (again, I'm REALLY not trying to pick on anyone).

[MrN2OBelvedere]

Wow this garnered more response than I expected. Thanks guys!

2grimjim is certainly right on one thing. I don't want to spend 500 on a set of forks for my bike.

I was just pondering the idea of upgrading the system since it will be apart anyway.

Ideally, the forks would just bolt right on. If I didn't have to change the clamps, all the better.

I'm going to attempt to break these options down into a digestible form:

Option 1: Rebuild the forks I have, using race tech's complete system

Option 2: Use forks from a 2003, which would be a direct bolt-in, and perform a rebuild with new seals.

Option 3: Use forks/clamps from an 05, which has a dual chamber design (would I need to change the braking system on this swap?)

Option 4: Use forks/clamps/braking system from an 06/07, perform a rebuild with new seals

Option 5: Use 96-98 forks from a 250 or 400.

Option 6: 05 and up WR 450 forks/clamps

99-up forks use rubber bumpers instead of hydraulic lock for bottoming resistance

03 YZ's and 03/04 WR's use a tapered damper tube which is difficult to work on

Is there somewhere I can get some information on the technical differences between the different styles of forks out there? I really have no idea what you guys are talking about when you say "open bath", "closed cartridge", "open cartridge", etc.

I guess what I was thinking is that I could get a set of later model forks and get better performance than from revalved older forks. Same goes for shocks. It seems that the only option worth considering is the 03-05 YZ450 shock.

And just so you know, I'm not insulted. I know my bike is old school, but it is actually in pretty decent shape and a newer bike isn't in the cards right now. I'm not a pro mx-er and never will be. An extra inch of bottoming resistance would never be missed. I am more interested in overall performance and adjustability. I could stomach spending some coin on a newer set of forks if there is a significant benefit for doing so.

[moto2000]

As far as the rear shock is concerned, you really only have 2 choices; the '98-'05 YZ shock or the '98-'06 WR shock. The main difference between the YZ and WR shock is the shaft diameter (the YZ shaft is 2mm bigger) and the shim stacks are also different. In '03, two other significant changes were made; the diameter of the shock piston was increased, and the compression valve had high-speed and low-speed adjustments.

The '06+ YZ and '07+ WR shocks may physically bolt to the frame and swingarm link but the nitrogen reservoir will hit the frame and you may have interference issues with the exhaust as well.

Used shocks can be had for around $100-$150. I think the preferred one would be from an '03-'06 WR450 or a '03-'05 YZ450. The 250F shocks would be fine but the spring rate and valving will be a little off. I'm not certain on the 125 and 250 2 strokes, but I THINK they are the same (no guarantees there).

It must be magic....a '07 yz450 shock in a steel frame!

[2grimjim]

Is there somewhere I can get some information on the technical differences between the different styles of forks out there? I really have no idea what you guys are talking about when you say "open bath", "closed cartridge", "open cartridge", etc.

Well....lets see. The easiest way to convey the difference would be with pictures but I can't recall off the top of my head any websites with a graphic to link to, so....here goes;

Open cartridge forks (sometimes refered to as 'open bath' or simply 'cartridge fork') have a 'cartridge' (duh), or more simply, a tube with a rod and a piston inside, similar to the rear shock. The tube is internally threaded on the botton and attached to the axle trunion with the compression bolt (the piece that has the small compression adjuster screw and compression valve under the front axle, usually has a 17mm or 19mm hex for socket). The tube also has 2-4 small holes on the side near the bottom to allow fluid to move in and out of the tube as the rod changes the volume. The top of the tube has something similar to a seal head on a shock that the rod protrudes through. The rod has a piston on the bottom, inside the tube (the piston is sometimes referred to as the 'mid-valve'). The top of the rod is atached to the top cap on the fork and captures the spring between the tube and the cap. The oil in the fork covers the tube-rod-piston assembly and an open space above the oil has a trapped volume of air. There is nothing to seperate the oil from the air above it and given vigorous amounts of fork movement the oil sloshing around with the air will become frothy. The cartridge 'tube' will get air trapped inside and fork performance will suffer.

Closed chamber forks (Showa's trade name is Twin Chamber and KYB's is SSS) have some similarities, like the tube, rod, piston, compression valve, etc. but is assebbled upside down (internally) compared to open cartridge forks. The 'tube' or 'cartridge' is a closed unit. The rod end ataches to the axle trunion and the top to the top cap. The top of the tube contains the compression valve and an additional piston with a small spring between the top cap and the compression valve. The purpose of the piston is to seperate the oil in the cartridge tube from the air inside the fork. As the damper rod moves into the cartridge tube, it displaces oil. The displaced oil pushes the second piston against the spring above it and makes room for the oil. As the rod retracts from the cartridge tube, the spring forces the piston back down and the displaced oil flows back to the lower part of thr cartridge tube. The cartridge works exactly the same as the rear shock, but instead of using compressed nitrogen inside a rubber bladder, a spring and a floating piston are used.

[2grimjim]

It must be magic....a '07 yz450 shock in a steel frame!

Thats wierd. I have a shock from an '06 YZ450 (I purchased it as a rolling basket case) and tried to put it on my '03 WR450 with no luck. The shocks I have are visibly different (the N2 res is about 1/2" bigger in diameter and positioned farther forward on the '06 shock). If I remember right its not a problem until you actuall ride the bike. The shock doesn't stay in the same place as the swingarm moves. Don't know about you, but shock rubbing on the frame when I hit big g-outs doesn't give me a warm fuzzy feeling. I'll stick with my recomendation.

Don't know what to say.

Edited December 21, 2011 by 2grimjim

[moto2000]

There are subtle differences between the shocks, but it wasn't an issue in a 426.....weird

[2grimjim]

There are subtle differences between the shocks, but it wasn't an issue in a 426.....weird

OK, so the 400/426 has a little more clearance. But it was definately a problem on my '03 WR450. Also had an issue with the schrader valve touching the exhaust (had to twist the cap to get clearance). Way too close for me to leave it that way. It's been quite a while since I worked on a 400/426.

The photos really don't do justice to how much difference there is. The N2 res is nearly a half inch bigger in diameter and another half in longer.

On your machine how much clearance do you have? It looks kind of tight.

How much does the clearance change when the suspension is bottomed out?

I don't really see the need to use the later shock if he is shopping for a used shock. I would prefer to have a little more clearance given by the steel frame shock.

[MrN2OBelvedere]

moto2000 so you're saying that the 2007 shock might very well fit my bike?

Did you experience a noticable improvement with that shock vs. the stock one?