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      HOW TO: 4-STROKE PISTON REPLACEMENT DONE RIGHT!
MaxPower

2004 Fork Help

36 posts in this topic

I have both a 04 250 and 03 125. Love them both. Liked the forks until I got to ride a couple new Yamahas. The biggest difference between the 14 year gap were was the front ends. I realize there was a lot of development that went on throughout the years but there must be something I can do to get the forks on my bikes to be more plush.

According to the Race Tech Spring Rate Chart my springs are right there for my weight. There must be a way to get things closer with valving and oil . Im capable of working on my own suspension, just need some direction. At this time Im just not able to hunt down and buy more current SSS front ends although I know that would  be a great way to go. Any advice would be welcome-Thanks

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Have you replaced the bushings recently?

Worn bushings binds up the tubes increasing stiction and harshness.

 

What type of riding : MX or trail/off-road ?

If trail/off-road, your older open chambers are perhaps better suited for that than closed cartridge SSS forks.

Edited by mlatour

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I put Race Tech Gold Valves in my '03 fork/shock, couldn't be happier in the woods. Being as you're looking for "plush", I'm presuming you're not focusing on MX, so.. Spring the $$ for the Gold Valve kits, get RT's recommendation for building the shim stacks, and do it. Correct springs are a must, but all the springs do is maintain correct ride height, everything else is in the valving.

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Remember that your 03 are 46mm and the 04 is 48mm. You can make them very nice with valving or a rebuild even. Always align your fork tubes also. This will insure you ae not binding through the stroke.

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I'm using both bikes primarily for mx. Yes, fork alignment is important and I'm always certain to be sure the forks are running parallel.  Just changed oil in both recently. 

 

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When was the last time you rebuilt them? If the bikes are in constant use you can count on replacing the friction/piston/bushings, along with seals at least every two years. OEM kits are 48 bucks so it's a cheap investment. It's the KYB oil that costs. So any good 5wt oil is going to work for you. 135mm from the top is suggestion but it may very on rider, and tracks, or riding area.  

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On 18/11/2017 at 11:43 PM, MaxPower said:

I realize there was a lot of development that went on throughout the years but there must be something I can do to get the forks on my bikes to be more plush.

There certainly is, and it's a very easy valving change.

With some simple valving mods they can be plush without blowing through the stroke. Working great for fast trails and rough MX.

As mentioned already, firstly ensure the bushes and seals are good. Also ensure the spring rate matches your weight.

The stock base valve has 3.0mm ports. Carefully drill them to 3.5mm. Also carefully round the entrance lip on each hole you drill so they have the usual bell mouth style intake. This will substantially soften the very high speed damping. More like the SSS forks. 

In the mid comp valve, remove one face shim and put it back together. This will soften the stack and also widen the float gap. So you will feel much less vibration over chattery ground, and you will use more of the stroke over bumps.

The stock reb is good with the clickers around the 11 or 12 position.

Things to note:

The base port drill mod makes a big difference. So you might like to increase the damping in the base shim stack over stock.

This reduction in damping does mean you can bottom them out more easy, so your oil volume will probably have to come up.  Staying withing KYB's range does give good bottoming resistance right at the end.

I think the 48mm KYB fork works superb with Dexron VI ATF fluid.  Low cost, super slippery, and doesn't foam/fade.

Edited by numroe
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I agree with mlatour in that the older forks work just as good if not better than the newer forks for offroad. I'm not sure about jumping as I didn't do much mx but cornering is the same on a mx track or offroad. They are not plush by any means but its more about what you go faster on. I have found that the 36mm forks with stock valving work the best when undersprung and this takes the harshness out, 1 rate softer for mx and 2 rates softer for offroad. 1 rate is usually about 15 lbs. I had the older forks revalved by 2 different reputable companies and they never were as good as stock. The fastest I ever went on a dirt bike was a 2000 yz 125 with stock suspension with stock springs, valving, and fresh oil at the stock level when I weighed 195 lbs. I'm sure several will disagree but this is what works for me. I think the 38mm 04 forks have a little softer valving so maybe stock rate for mx and 1 rate softer for offroad.      

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I am new to TT, but man that's some good feed back! Would anyone know or be able to list what the comp valving stack should or would be? Thanks!

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On 19/11/2017 at 9:23 AM, numroe said:

The stock base valve has 3.0mm ports. Carefully drill them to 3.5mm.

My error there. They are 3.5mm ports stock. Drill to 4.0mm.

8 hours ago, Buzzymoto said:

Would anyone know or be able to list what the comp valving stack should or would be?

Sure.  Base comp shims (after drilling the ports) can remain as stock. That is: 6x24.12 12.12 22.15 20.25 18.15 16.15 13.15 11.25b

The drilled ports makes a huge difference, so if you plan to ride some faster MX with the 48mm OC KYB forks, then instead of beefing up the stack, maybe drill just 2 or 1 port, instead of all three. I chose to drill all three ports and run a base stack which is 105% as stiff as stock.

Mid comp with one face shim removed becomes: 2x27.1 20.1 16.1 2x14.3b.

In the mid valves, I don't remember if the face shims have support on super fast impacts or if they blow open a long way.  If they blow open a long way, then these face shims might get deformed after a while. Which I think is a worth while performance mod.  

I have the mid comp float gap recorded as 1.5mm stock and 1.6mm after the shim removal. But I'm not sure how carefully I measured that.

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Thanks for the reply! Would there be any advantage or disadvantage to preloading the spring? For example a spacer on top of the spring. I noticed my 2004 yz250 does not have any thing..

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15 hours ago, Buzzymoto said:

Would there be any advantage or disadvantage to preloading the spring? For example a spacer on top of the spring. I noticed my 2004 yz250 does not have any thing.

Preload makes a big difference in these forks. Like most or any.

The stock 2004 fork springs have none. They rattle loose in there. I guess it was a quality control issue that made it into production. 

I went for softer springs in my bush forks. I tried 2.5, 5 and 7.5mm preload and found 5mm to be the best. The tiny ride height difference was  easily compensated by the fork clamp height.  The preload change was easy to feel by the way the front tire tracked and how connected it feels to the dirt.

They're awesome offroad forks when dialed in.  Low stiction and feel nice. I  love them. Old tech that works really well can be real surprise if we get used to consuming modern day marketing hype. Sometimes things are not made like they used to be too. 

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I to have a 2004 YZ that I use for fast trail and enduro style riding. All parts, bushings and that are perfect. They have hurt me ever since I've had it. ( got it brand new in 08)  The only way it can feel good to to get up on it, and shift weight loaded forward, and ride faster that I want to go, ( sometimes) and I don't always want to do that, and I'm tired of it damaging my shoulders and joints. I want to ride, but it's just no fun.  I'm not intimidated to rework/drill / modify a valve stack, but nothing is mentioned here ( or I overlooked it) about the internal cartridge, it's valves or oil .. etc etc.  So, can I take it apart (yes) and do something in there that will help? 

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1 hour ago, TommyTodd said:

I to have a 2004 YZ that I use for fast trail and enduro style riding. All parts, bushings and that are perfect. They have hurt me ever since I've had it. ( got it brand new in 08)  The only way it can feel good to to get up on it, and shift weight loaded forward, and ride faster that I want to go, ( sometimes) and I don't always want to do that, and I'm tired of it damaging my shoulders and joints. I want to ride, but it's just no fun.  I'm not intimidated to rework/drill / modify a valve stack, but nothing is mentioned here ( or I overlooked it) about the internal cartridge, it's valves or oil .. etc etc.  So, can I take it apart (yes) and do something in there that will help? 

What don’t you like specifically? Does it feel like you are on a pogo stick? Or riding on top of the dirt rather than digging into it?

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I put some thought to this, seems like, from the first inch of travel throughout the entire stroke, I'm feeling every small hit as a big one, (choppy hardback) and the medium to hard stuff is overly harsh. It tracks pretty good, but I feel everything. (2-3" log crossing, rocks, roots etc) Does ok on bigger hits, when it gets around the 70-80% compressed stage. But, there again, takes too much energy from me, and harsh enough in the first 2/3 stroke, the forkfeedback,.. it's actually painful. Mid B, older rider. I'd like controllable plush these days.

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Over the past two seasons I went thru about 14 or so experiments re-valving my CRF250X forks for moderate speed rocky trail riding,

got them much better but came to a point where nothing else seemed to improve things until I figured out

the rear shock was now un-balanced versus the softer re-valved forks.

 

My un-scientific explanation: the overly stiff shock compression damping was transmitting deflection back into the front end,

by the time the forks had absorbed the hit and were about to rebound, rear end deflection would add another 'hit' in the forks.

Switching to a stiffer shock spring which requires less preload also made a less 'front heavy' feeling while riding.

 

For low speed stuff I too was looking for a super plush ride but realized thru experiments you come to a certain

point where it negatively affects handling and stability even at moderate speeds so, have since gone back to slightly stiffer settings. 

 

Same lesson learned on my MX track ridden YZ125, spent a lot of time fine-tuning the forks with Race Tech Gold Valves

but never bothered much with the rear shock settings. Forks now feel great on jumps but handling still need some improving.

Now, my front end bite issues at corner entry are best tuned by adjusting shock preload and rebound settings.

 

Edited by mlatour

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Rear shock had been revalved, re sprung for my weight, and is itself near perfect in operation.

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On 2/6/2018 at 10:46 AM, TommyTodd said:

I want to ride, but it's just no fun.  I'm not intimidated to rework/drill / modify a valve stack, but nothing is mentioned here ( or I overlooked it) about the internal cartridge, it's valves or oil .. etc etc.

You just overlooked it. See my previous posts in this thread.

When I mention the "mid-comp valve" that's the valve inside the cartridge. Undo the stack, remove one face shim. Reinstall the nut with blue loctite on clean threads. Put it back together. Your carts are done. To pull the cartridge apart carefully drill out the factory stake/lock points, then unscrew the end piece. Use soft jaws when you use a vice.  Reassemble with blue loctite on clean threads.

Then drill the base valve ports 0.5mm large and smooth the port lip on the expose intake side. Put the whole fork back together using Dex 6 ATF. Guess you know about remove/install the base valves using an impact wrench. Push a spring down inside the fork firmly if a base thread wont disengage, then hit it again with the rattler. Be careful to not damage the o-ring seals when you install the base valves. ie. put oil on them and don't burn them by over speeding the rotation.

Keep your work place spotlessly clean. Have ample brake cleaner spray and an air gun handy.  I lay paper towels on by bench every time I work on suspension.

Everything you described can be resolved with these mods.  You will love it!! The 48mm OCs are awesome forks for the bush. Low friction, smooth damping, stiff tubes so good control.

Tune the oil level for the travel vs bottoming resistance you need. These forks have a nice bottoming resistance too. I think I'm about mid way on the oil level, and I get good travel but it super hard to clunk them.

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On ‎11‎/‎21‎/‎2017 at 5:29 AM, numroe said:

They're awesome offroad forks when dialed in.  Low stiction and feel nice. I  love them. Old tech that works really well can be real surprise if we get used to consuming modern day marketing hype. Sometimes things are not made like they used to be too. 

Damn, you've got me wanting a 48mm fork YZ, bad! Already have the 2006 YZ125, 2013 KTM, kids bikes, street bikes ... shed's too full!

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8 hours ago, numroe said:

You just overlooked it. See my previous posts in this thread.

When I mention the "mid-comp valve" that's the valve inside the cartridge. Undo the stack, remove one face shim. Reinstall the nut with blue loctite on clean threads. Put it back

Numroe .. I normally use a really good quality fluid. Motorex, Silkolene etc.

Would be interested in what level from top your fluid setting is with Dextron 6 ATF.  (after cartridges are full etc)

I'm prepared to reduce the springs to .38kg Stock I believe is  .42kg.     

I'm pretty excited, I'd really lost hope but felt there was an answer. There's nothing to lose!  Tommy

 

 

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