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I'm doing Hare Scrambles/XC racing on a 2002 YZ250. I'm a 6'2" 190lb "Fast C Rider". I also play ride MX, and want to give racing MX/GP/Megacross a shot, but the forks are holding me back. 

 

For the rear end, I've set the race sag to 100mm. I had to add a lot of preload ("tightened the nut" about an inch), so my bike sag is less than ideal now, which I understand indicates I should try a stiffer rear spring. What are the handling effects of running this way? Simply setting the sag helped the bike's manners an amazing amount. I was terrified to jump this bike before setting sag (hello boner air!), but after, it is much easier. It launches neutrally on most jumps now. I'm running full soft (out) on high speed compression (helps the rear stay put on rooty hill climbs, etc), and a few clicks out from stock on the rest.

 

RT calculator says to go from 4.8 kg/mm stock shock spring to 5.4 or 5.6 kg/mm.

 

The front end is not going so well. I've changed the fork oil and have been playing with clickers and oil level.  No matter what I try, the front end is still too harsh on small stuff, and far too soft on big stuff.  Clicking them to the bottom is a regular thing in play riding as well as racing.  I can also feel and see the forks spending most of their time at the bottom of the stroke. I'm very budget-oriented, so I'm thinking about going ahead with stiffer springs with the stock forks and valving. Is that a mistake? In addition to springs, should I buy a tanks kit? Gold valves? Drill my valves? Should I skip springs for the 2002 forks (KYB 46U), and instead shop for 2005 AOS forks (~$200), or the 2-3x pricier 2006 SSS forks, and then buy springs for those? Should I plan to pay for a revalve for these forks after a swap? I'm feeling more than a bit lost here LOL.

 


 

RT calculator says to go from 0.43 kg/mm stock fork springs to 0.48 or 0.50 kg/mm. Same rate but different size/part number for 05 or 06+ forks.

 

Photos of the bike, to keep this interesting:

 

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14699338002_8b5bb6be69_c.jpg

 

14697232054_f490ab1d7e_c.jpg

 

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At 190 pounds, your first step should be to get stiffer springs.  I'm not sure about the RT recommendations (seems a bit stiff in the front), but the stock stuff is definitely on the soft side.  Not saying that will totally resolve your issues, but it will help.

 

Note that drilling your valve probably won't help your situation, and gold valves themselves won't either (however, the access to RT's valving knowledge base could, if applied properly).  The later CC forks are really good, but you can probably make your forks work quite well with some valving changes and the right springs.

 

Finally, note that having a bike that is tractable, plush, and hooks up well in XC/scramble, especially for a C rider, is very hard to balance with big bottoming resistance for MX.  Since I focus on XC/HS, I gave up on having a MX-capable setup on my bike.

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Try springs first as kyle says , you can get second hand ones from most tuners

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Thanks guys. Kyle, I agree about the difficulty of setting up dual purpose machine. A lot of my play riding is on a GP-style course, though (hills, ravines, tight singletrack, and some MX obstacles and jumps), and several other bikes that I have ridden on the same track have suspension which works much better than mine does for all of it. Specifially an 08 YZ250, 06 CRF250R, and 14 TE250, all very different handling machines, with vastly different spring rates and settings, but all of which had front ends which worked  better than mine for all of the varied terrain.

 

Mog, I hadn't thought of asking local tuners for used springs. I like this idea. :)

Edited by mellephants

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All of those have much more modern suspension , If you don't mind the expense the later yz fork is a good option , I would not get the 05 fork

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I called a few local tuners, had some good conversations, and read a lot more on this subject online. Looked like 100+ for springs, then 250+ for valving mods and rebuild. For that price, if I'm smart and lucky, I can get an SSS setup with spring rate that is close to correct. For example the YZ450F's come with 0.47 kg/mm springs from the factory. Then next season, if desired, I could revalve the SSS forks for even better performance.

 

I'm looking around for deals on some 2004 triples (magic year with steel frame and 48mm forks), and 06+ YZ forks. I'll update thread with whatever I wind up getting my hands on.

 

deliver.png

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I found everything for the swap. eBay had the best prices. Here's what I paid, including shipping:
 
$240.00  2009 YZ450F forks and axle
$68.75    RG3 top triple clamp from 2004 YZ250F
$32.47    D1H lower triple clamp from 2004 YZ450F
$24.99    Race Tech fork guards for 2008-2009 YZ
$12.99    Aluminum brake line clamp
=
$379.20 TOTAL
 
I was able to call the fork seller before bidding. The forks should be unmodified, from a bike with only 50 hours on it. The 09 450's came with the SSS forks and 0.47 kg/mm springs, so they should be close enough to correct for me to use without new springs. I hope to just bolt them on and ride for the rest of the season, then rebuild them over the winter, either just new seals and fluid, or with some tuning to suit me even better.
 
The 2004 YZ's had steel frame and 48mm forks, so the 2004 clamps should work with my 2002 frame and the 2009 forks. I plan to re-use my stock steering stem, and a set of new stock size bearings.
 
I'll also probably sell off the stock 46mm triples and forks, hopefully make about $100 back from those, putting this swap under $300 cost.

 

Will my plan and these parts work? Comments/advice/etc are very welcome. 
 
Seller images:
 
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FZ6Cofz.jpg

 

4oYTZFI.jpg

 

33mxn4W.jpg

Edited by mellephants

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I've been stuck in yamaha 2 stroke since I've joined.. I never knew it was a section dedicated to suspension.. TT is the $hit!

A lot more info here than I thought. Everytime  I search on google I get the same results.. awesomeness

 

Sux I got to go to bed bc of work after finding this lol

Edited by yz250474

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I just did the same swap on my 03. I think you're about set, except for brakes. You'll need the cable with shorter routing and possibly a different caliper or bracket.

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I started doing this swap last night. I brought everything over to my brother's house, since he has a hydraulic press. Unfortunately, his press was not quite tall enough to fit the stem into, so I was not able to finish last night. My brother was kind enough to take it to a big press for me today, so if that goes well, then I will try to assemble everything tonight.
 

I just did the same swap on my 03. I think you're about set, except for brakes. You'll need the cable with shorter routing and possibly a different caliper or bracket.

 

Good note. Luckily I had already swapped to a complete 2007 Honda CRF450R front brake (caliper, line, and master). For the 2002 YZ forks, running the CRF brake requires re-using the 2002 YZ bracket. The caliper slide bolts line up. For the 2009 YZ forks, I believe the 2007 CRF brake bracket will fit.

I hope it all works out, because I am planning to do MWXC Round 7 in Bridgeton, IN on Saturday, then Fly Showdown Series Round 5 at Crossroads MX in Mason, IL on Sunday.  :ride:
 

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I started doing this swap last night. I brought everything over to my brother's house, since he has a hydraulic press. Unfortunately, his press was not quite tall enough to fit the stem into, so I was not able to finish last night. My brother was kind enough to take it to a big press for me today, so if that goes well, then I will try to assemble everything tonight.

Good note. Luckily I had already swapped to a complete 2007 Honda CRF450R front brake (caliper, line, and master). For the 2002 YZ forks, running the CRF brake requires re-using the 2002 YZ bracket. The caliper slide bolts line up. For the 2009 YZ forks, I believe the 2007 CRF brake bracket will fit.

I hope it all works out, because I am planning to do MWXC Round 7 in Bridgeton, IN on Saturday, then Fly Showdown Series Round 5 at Crossroads MX in Mason, IL on Sunday. :ride:

Cool, let me know when you're ready to dive into a revalve. I've got mine perfect for GP/GNCC style offroad, I'm trying to dial in a little more rock and root compliance for the tight woods we get into here.

Edit - oh yeah, and I'm also running a Gorr 295 to make it a complete Frankenbike!

Edited by C-P

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Cool, let me know when you're ready to dive into a revalve. I've got mine perfect for GP/GNCC style offroad, I'm trying to dial in a little more rock and root compliance for the tight woods we get into here.

Edit - oh yeah, and I'm also running a Gorr 295 to make it a complete Frankenbike!

 

 

Will do. Sounds awesome.

 

The stem is pressed into the lower, and I have all the new bearings greased and installed.

 

Right now I have just noticed my triple clamps appear to have different fore-aft offsets. Not sure how I could possibly be doing this wrong. I may be out of luck until I buy a different top or bottom.

 

Top is RG3 for 2004-2005 YZ250F

Bottom is D1H for 2004 YZ450F

 

I had assumed they would have the same offsets. I guess the seller's bike had a different lower as well.  Here's the auction: http://www.ebay.com/itm/321466493371

 

:-/

Edited by mellephants

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The RG3 has part number YZ2219054.

 

 

RG3 application chart: http://www.rg3suspension.com/p_triple_clamps_applications.php

 

They say stock offset is 25mm and recommended is 23mm. So mine is probably 23mm. I will call RG3 next week to confirm, then I can start looking for a matching offset lower, or a stock offset upper. 

Edited by mellephants

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Wouldn't hurt to try the 23s, some people swear by the reduced offset. But you can sacrifice stability.

I pretty much bought a whole 07 250f front end to do the swap, including the caliper, then just swapped stems. 450f parts would have saved me some hassles for sure. Good luck!

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Good call on the upgrade of the forks.  Had 02 & 04 YZ250's & never came to grips with the suspension or handling of the bikes even after Enzo did some work & sold them for that reason.  The 06+ KYB stuff is much improved. 

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Thanks for input C-P and H4L

 

Good news! The RG3 seller was very cool about it, and is going to do a refund/return for me, and I was able to find a stock offset RG3 clamp from a 2005 YZ250. This time I confirmed with seller that the clamp was used with a stock lower triple clamp. If it comes in time I may be able to get it installed and tested this weeked :-)

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All the parts laid out for the first attempt to install:

 

14961868645_d2f0972aa2_b.jpg

 

Friday night, after realizing the top triple was not stock offset, reassembled using stock forks and beer can shims on the lower triples: 

 

14961862975_6e5be51e38_b.jpg

 

The shims worked well enough for an XC race on Saturday ...

 

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... and a Moto race on Sunday

 

14646781419_6717994f4d_b.jpg

 

14937971036_332c70e483_b.jpg

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I don't have any more assembly photos, but after returning the original clamp for a full refund, I found and bought another RG3 clamp. This clamp is stock offset and cost $85, bringing the total swap cost to $397.45 ... not too bad!

The CRF bracket and brake fit perfectly, and I wound up grinding about 9mm off the non-brake-side spacer to allow the '09 axle to fit properly. There is some leeway with this spacer. I ground it on the "large" side of things, so I may go ahead and grind it down a bit more for a slicker fit.

The forks are working great! I have play ridden twice, and raced one XC race with it. I found they allow me to push a LOT faster when I have the energy, especially in really rough fast sections. The difference on jumps is pretty awesome. Both takeoff and landing are easier and more consistent. I'm starting to have the confidence to really "send" things on this bike now, where before I would be sweating with fear all the way up the face :)

Play riding:

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Race:

14962057295_b73f0e2dce_b.jpg

Edited by mellephants

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Placed 4th in C Open and 49th overall at Stoney Lonesome AMA HS last weekend. The bike worked very well, although I accidentally ran too much rear tire pressure (~14psi), and when I realized it, I just kept riding instead of stopping. In retrospect I should have stopped to air down to 8 or 10.

The suspension worked well overall. Fantastic on the MX sections, but still pretty harsh on the high speed roots and rocks. The course included a lot of 60 year old "club trails". These were some of the most tiring trails I've ever ridden. I could see the set-up woods bikes just flowing through things that would make my bike buck and jump. The "jump over it" strategy worked sometimes, but for the most part I wished for gentler valving on both ends.

I plan to run my compression clickers (and rebound?) almost all the way loose for the next HS (MWXC Sunday). I'll then probably set them back to where they are now for an AMA GP on Monday at LTM in Casey, IL.

Photo from Stoney Lonesome's MX section:

14871270860_6773039a65_b.jpg

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