Posts
20
Joined
3/18/2014
Location
White Heath, IL, USA
Edited Date/Time
1/21/2016 2:18pm
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:
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:
I have a '03 YZ250 that I just put SSS stuff on. The forks, clamps, and shock I used were from a '09 YZ250f so I had to swap the steering stem from my '03 clamps into the '09 clamps. I paid $400 for the stuff I got and it was worth every penny!
I have a '13 YZ250 as well and I can barely tell the difference between the two now.
$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:
[img=https://i.imgur.com/Q4pAzMN.jpg]
[img=https://i.imgur.com/acVAvmu.jpg]
[img=https://i.imgur.com/FZ6Cofz.jpg]
[img=https://i.imgur.com/4oYTZFI.jpg]
[img=https://i.imgur.com/33mxn4W.jpg]
The Shop
Luxon 4-Post Bar Mounts
$189.95 - $239.95
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Axle part numbers are similar but different FWIW
2002 YZ250 front axle
5BE-25181-00-00
2009 YZ450F front axle
5XC-25181-G0-00
Similarly, the "wheel collar" part numbers also have matching center strings in the PN.
PRO: I should be able to use my 2002 axle, etc.
CON: I won't get whatever increased performance is associated with that change. ^_^
http://www.thumpertalk.com/topic/1003475-figured-out-how-to-swap-07-48m…
I should have all my parts by this weekend, and maybe even have time to put it together and try it out.
I had the same bike (I also rode it in the woods) and it was my favorite YZ250 engine (in 2003 they modified the porting and decreased the crank MOI to make it revvier for MX. The engine is the same from 2003 through today).
It has really good bottom-end and a broad spread of power. I put a FWW on it and loved it.
However, the forks sucked... as you know. Harsh and very hacky.
Terry Hay gave me some really good info on disabling the CV (?) valve in them and a valving stack to try. Worlds better. Probably not better than the SSS forks (I know, I've got 3 Yammies with those forks) but totally livable for woods riding.
This is what I was going to suggest for you with the "budget conscious" restriction.
Good luck and let us know how you like them.
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
I found part number YZ2219054 on it. 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.
[img=https://farm4.staticflickr.com/3886/14961868645_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:
[img=https://farm4.staticflickr.com/3890/14961862975_6e5be51e38_b.jpg]
The shims worked well enough for an XC race on Saturday ...
[img=https://farm4.staticflickr.com/3905/14937741616_3c85ac652f_b.jpg]
[img=https://farm4.staticflickr.com/3908/14836214084_6b372d31e9_b.jpg]
... and a Moto race on Sunday
[img=https://farm3.staticflickr.com/2903/14646781419_6717994f4d_b.jpg]
[img=https://farm6.staticflickr.com/5553/14937971036_332c70e483_b.jpg]
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:
Race:
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:
Pit Row
http://www.thumpertalk.com/topic/1096143-2002-yz250-suspension-setup/
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