29 replies to this topic

[sps3172 TT Member]

I realize the basic fork swap has been covered many times before.  However, after what feels like a thorough search (both here and anywhere I could think of...), I'm left with much confusion.

I have a 2005 YZ250 2-stroke.  Back in 2009, I decided that I wanted to upgrade to the newer style 'SSS' fork.  After reading all I could about what parts would be required to make this swap, I bought the following parts.

- 2008 YZ250F (4-stroke) forks
- 2008 YZ250F (4-stroke) shock
- 2008 YZ250F (4-stroke) triple clamps
- 2008 YZ250F (4-stroke) front break (caliper and master cylinder)
- 2008 YZ250F (4-stroke) front axle

I planned on having the longer steering stem pressed out of my 2005 triple clamps in into the 2008 250F clamps, and then having the whole mess re-valved.  I confirmed that all the parts would bolt together but then...life came along and this project (and my riding) has been neglected since then.

I've got time for dirt bikes again!! YAY!!  However, as I attempt to pick back up where I left off, I noticed something odd/disturbing.  The 2008 250F forks are 12mm shorter in overall length (axle CL to top of tube) than my 2005 250 2-stroke forks.  I knew the headtube was  longer on the 250 2-stroke (hence the longer steering stem) but I presumed that the lower clamp just sat lower down the fork leg.

Can someone make some sense of the fork length discrepancies?

Were all the 2008 forks (250F, 450F, 250 2T, 125 2T) the same length or did I buy the wrong ones for my 250 2T?

If they were all the same length in 2008, how does one account for what seems to be a 'front low' attitude vs. the attitude with the longer 2005 fork?  Was the 2008 fork shorter as well?  Was the linkage somehow different?

This fork swap has turned into a big MESS.  

Help!  Thanks!

[CaptDan TT Addict]

I believe that starting in 2007 the YZ125 & 250f received shorter lower fork legs. The numbers I have heard are 5mm, 7mm, 9mm, and now 12mm shorter.

All other major parts in the forks are common with the 250 2T & 450.
This can be verified in the parts lists.

Lots of guys have already done this swap, just be careful when you do your suspension set-up.

[jeffro667 TT Bronze Member]

If this is any help at all, I just measured my stock 06 YZ250 from the top of the head tube on the frame, to the center of the front axle is 35.5 inches. My forks are slid down to the line, 5mm i think. I just took this measurement because I'm possibly doing a fork swap, and  I don't want the same issue.

Depending on what you weigh, those 08 250F components may be just right for you. I think the forks have .45's stock, and a 5.3 stock shock spring.

[BDubb106 Get Help Now]

Yes, the fork length was shortened in 07 on the 125/20F as Captdan stated. I believe the 250/450 forks are the better fit to keep everything "lined up". Ill go out and measure the forks on my 08 250 and post results back.

[adam728 TT Addict]

Don't forget that the 05 fork has SLOP, not preload, on the main spring. So actual ride height won't differ 12 mm (unless you've changed springs / added prelaod to the 05 forks).  Typically it's around 5 mm of play fully extended.

So if you have the same spring rate, but 5 mm of slop on the 05 fork springs, and 5 mm of preload on the 08 fork springs, then you are going to end up with only ~2 mm of effective difference in length.

Is the shock the same length, or does it bring the back down a little as well?
And of course, your linkage question.

[Miller227 TT Newbie]

sps..i understand your confusion on this topic as i just went through this recently as well. On my 05 yz 250 i found out that 07 yz 250f suspension was put onto the bike. The way i found this out was that i had my suspension being revalved and sprung correctly for my weight. My suspension guy asked me if these were the right forks because the springs inside measured 12mm shorter than what the factory specs were. once i get them back this week, i am going to measure them along with my 09 set up to see if there is an overall difference of the fork itself.

i have learved that the transfer can easily be done with all of things that you purchased with ease. my top triple clamp is a pro taper brand but the bottom is still the same from 05. everthing seems to line up good and there isn't any bowing to my knowledge.

[Riley88 Member]

I want to revisit this.  

I have a 2005 YZ 250.  I've had my forks revalved by Enzo in 2009, and then Smart Performance in 2011.  My forks are awesome in some aspects, but really suffer overall.  I rode a friend's 2007 YZ250f, well undersprung for my weight, and they felt much better on the track for everything except bottoming.  

I'm at the point where I need to do a rebuild on my forks anyway, so I went ahead and bought a set of 2007 YZ250f forks from that auction site.  Pretty good deal.  Now I'm trying to decide what exactly I need to do to bolt them on.

Obviously I need to get them revalved and resprung for my weight, etc.  But, as I understand it, I also need to:

-Buy a 2007 triple clamp set.
-Put the 2007 set on my 2005 stem.
-The spacers and axle are the same, or close, so I do not need to replace these items.
- 2007+ front number plate.

I've read different things about the brake hangers - do I need to do anything with the brakes and/or brake mounts?

Is that everything?

[Riley88 Member]

Que?

[YZrider2112 TT Bronze Member]

Riley88, on 22 October 2012 - 02:15 PM, said:

I want to revisit this.  

I have a 2005 YZ 250.  I've had my forks revalved by Enzo in 2009, and then Smart Performance in 2011.  My forks are awesome in some aspects, but really suffer overall.  I rode a friend's 2007 YZ250f, well undersprung for my weight, and they felt much better on the track for everything except bottoming.  

I'm at the point where I need to do a rebuild on my forks anyway, so I went ahead and bought a set of 2007 YZ250f forks from that auction site.  Pretty good deal.  Now I'm trying to decide what exactly I need to do to bolt them on.

Obviously I need to get them revalved and resprung for my weight, etc.  But, as I understand it, I also need to:

-Buy a 2007 triple clamp set.
-Put the 2007 set on my 2005 stem.
-The spacers and axle are the same, or close, so I do not need to replace these items.
- 2007+ front number plate.

I've read different things about the brake hangers - do I need to do anything with the brakes and/or brake mounts?

Is that everything?

Haven't done a swap like that, but I do know the 250f got the smaller brake caliper and bracket in 2007. Yamaha added it to the two strokes in 2008.  You will definitely have to swap something out on the brakes, but I don't know for sure if you can just slide the new style bracket on the old style caliper.  They may not work together, in which case you'd have to buy a used caliper off of an 07+ 4 stroke or 08+ 2 stroke.

Sounds like it will be a nice upgrade for you though.

[Riley88 Member]

Yeah, I seem to remember reading something about that a few years ago when I was considering this same thing.

I'll have to dig into the search function and see what else I can find.

[mattman122 TT Silver Member]

I just bought a set of 07 250f forks with triple clamps and axle for cheap on eBay. So am I for sure going to have to swap stems? And will I have to get a new caliper? Also is there anything different in the 05 shocks from the new ones aside from the Ti spring?

[CaptDan TT Addict]

mattman122, on 25 October 2012 - 01:18 PM, said:

I just bought a set of 07 250f forks with triple clamps and axle. So am I for sure going to have to swap stems? And will I have to get a new caliper? Also is there anything different in the 05 shocks from the new ones aside from the Ti spring?

You should not have to change your stem if you have a YZ125. If you have a YZ250 you will need to swap stems.

I believe you will need a smaller new-style caliper (like YZrider2112 listed above).

The rear shock received a larger reservoir and shock shaft in 2006. Overall eye-to-eye length is unchanged.

[kijen TT Bronze Member]

I put a complete 08 YZ250f front end on my 05 Yz 250, swapped the stem, put 08 caliper on it, put a 08 rotor to go with the caliper, stood the 05 and 08 forks side by side, maybe 4mm differnce, probably less, when side by side to my sons 09 yz 250 you can not see the difference ot feel the difference when going between bikes.  I only ride a couple times a months so I'm no expert, my son is a B class MX'r and is just worried about going fast, softer or stiffer but never comments about either handleing different.  I'd say get the best deal possible and set it up like any other fork, spriong revalve etc and ride...

[mattman122 TT Silver Member]

CaptDan, on 25 October 2012 - 02:44 PM, said:

You should not have to change your stem if you have a YZ125. If you have a YZ250 you will need to swap stems.

I believe you will need a smaller new-style caliper (like YZrider2112 listed above).

The rear shock received a larger reservoir and shock shaft in 2006. Overall eye-to-eye length is unchanged.

Yeah I have a 250. I guess I am going to have to locate a new caliper.

[RCannon]

You dont really need an entire caliper. If you find the hanger, the old caliper will slip right on the pins.  It crazy how much this stuff changes, but still works together.

[eazrider TT Bronze Member]

Overall shock length, eye to eye, '05 and later 2 and 4 strokes is 3 mm longer on the later models. That, coupled with the stated 12mm shorter forks will make your bike feel like a stink bug compared to the old geometry. Will require sliding your tubes much farther down in the clamps to get it to turn properly...Just found all this out as I converted my '05 forks to '06 SSS...Also was having my '05 shock revalved, and found some scoring on the inside of the shock body, needed to be replaced at a cost of 450 smackers. I thought I could pick up a later shock, and that's when I found the difference in shock length. ended up scoring an earlier shock body on line for 35$ or so...instead of 450 for a new shock body...

[jar944 TT Gold Member]

Just swap and adjust/tune to get handling you want.

i have 06 250f forks on my 07 frame with 06 clamps using a 02 stem. the brake is a 02 hanger with a 06crf450 brake system. The rear is a 09 250f swingarm and linkage with a 02 (or 06 depending) shock and  a 08 450f caliper running a 02 hub.

you can really really mix and match to get what you want.

[CaptDan TT Addict]

^^ Borderline Mad Scientist ^^

  

[CaptDan TT Addict]

eazrider, on 26 October 2012 - 09:25 AM, said:

Overall shock length, eye to eye, '05 and later 2 and 4 strokes is 3 mm longer on the later models.
...I thought I could pick up a later shock, and that's when I found the difference in shock length.

Very good info. I thought Yamaha rear shock length has been unchanged since the mid-1990's.     

[cwtoyota TT Gold Member]

Some data I've collected today with a tape measure:


2002 YZ250 = 36-3/4" (933.5mm)
2008 YZ125 = 36-3/4" (933.5mm)
2010 YZ250 = 36-3/4" (933.5mm)

2006 YZ450F = 36-15/16" (938.2mm)
2009 YZ450F = 36-3/4" (933.5mm)

All lengths are from centerline of front axle to the top of the upper fork tube (not including the fork cap) with the bikes on a center-stand to fully extend the forks.
The 2009 YZ450F forks are not currently installed on a bike, they are spares.

My measurements are probably accurate to +/- 2mm. They clearly show that there was a difference of about 5mm overall length between 2006 and 2008 SSS forks.

I would venture a guess that the change came with the change in 2007 YZ-F and 2008 YZ models when they received the smaller brakes and the smaller axle blocks on the forks.

I also took a measurement of a 2006 YZ250F shock that I have... It is 19-1/2" eye to eye length.