2006 YZ250F KYB SSS into 2009 EC300
 

So...... having lurked here for a few years and reading multiple fork conversion threads I've finally taken the leap and started this conversion for myself

Thanks to the copious amount of info on here, I had a great starting point to narrow down potential forks and hopefully avoid any costly mistakes

After a few weeks of serious searching I picked up a set off a 2007 YZ250F, including the front axle, spacers and GYTR triples through a private sale for about $100 less than most forks were selling for online or through wreckers. I'm on a limited budget, so this now gives me some wriggle room to cover unexpected costs.

The forks look to be well used, but (hopefully) mechanically sound

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My original plan was to keep the gasser triple clamps and pickup up a set of forks with the 35mm lug offset and bore out the top triples to suit the larger OD of the SSS's. Anyhow, these came up with triples for a good price so I'll be using them, with the bonus that this conversion would be reversible should I want to refit the Sachs forks when I sell my bike (I'd like to think a newer gasser or beta is my next ride, so the SSS's may be longer term forks)

Conversion plan for now is something like this:

- use the gasser front wheel (tubliss already set up front and rear) and brakes

- source the correct headstem bearings to fit the Yamaha triples to the gasser

- fit a simple rubber steering stop to the frame

- use the Braking oversize disc bracket (Part POW103) to fit my existing brake caliper to these forks. I'll ignore the speedo pickup for now

- research and hopefully source front wheel bearings with a smaller inner diameter to fit the 20mm YZ axle.

There was a thread on here somewhere where someone mentioned that older bearings had a 20mm inner, but the same OD as a later model hub. I figure then that I can get simple spacers made up which is a much easier path than the funky custom spacers that some have used.

Having never worked on these forks before, I think my first step will be to educate myself on servicing them and open them up and see what spring rates they have

From there I'm not sure whether I'll throw fresh oil in them and throw them on for a test, or ship them straight them off to a tuner for some generic off-road valving

My son also has a YZ125 with very firm SSS's that we've yet to service either, so at the very least I may open them up and see what setup is in there on the off chance that swapping components may save me some cash

At this point I'm also unsure on what's different between the OEM and GYTR triples apart from then having adjustable bar positions, but hopefully the overall offset is that same as OEM (the lower clamps are OEM)

Bear with me guys, this'll be a slow conversion



EDIT: these forks have been confirmed as 2006, not 2007 forks which run a different lug and offset. I'll update the thread title when I work out how to





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1999-2003 front wheel bearings are different in a couple of ways. They have a smaller ID, same OD, but they have are narrower (thinner/shallower) as well if I remember correctly. So you would need new spacers regardless. So if you go the 99-03 bearings route, you will need to source or make an inner spacer to fit the new axle and the bearing inner faces.

Thanks pscook, I hadn't considered whether they'd be thinner or not

I might chat to the local engineering place to see if they can easily manufacture something before I pick a direction with this, but the old bearings did seem like a logical path.


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Subscribed. I am thinking about doing this to my 02 later this year if I accrue the necessary funds.

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Thanks to some advice from F5 in this thread, I think I have a path ahead with my bearings and spacers:

what forks to use

https://r.tapatalk.com/shareLink?sha...4&share_type=t

At this point I don't have the forks in my bike, so I fitted the triple clamps and securely hung the whole assembly vertically so that I could freely fit my wheel in this setup using the YZ 20mm axle, the GG wheel and the existing GG spacers (from the 25mm axle).

After a lot of stuffing around I got the wheel pretty centred (within 1mm I think), and then delved into my box of washers and found out that 1.5mm thick washers were a nice fit in the gap left between the GG spacer and the fork lug

As this gap was exactly the same on each side, I'm assuming that the GG wheel runs the same hub offset as the YZ. This desk gives me some confidence that my centring was accurate

So, the total spacer length required is 25mm (existing spacer) + 1.5mm gap = 26.5mm

As I'm swapping out the existing OEM bearings for a set from a 99-03 Gas Gas (42mm OD and 20mm ID), I'm expecting the spacer length to be 3mm shorter as these bearings are thicker, bringing it to 23.5

This is a few mm longer than the 22mm suggested by F5, but our setups may be slightly different and there are a lot of variables

I have enough info now to go ahead and order the older bearings and see if my local GG supplier can source a 20mm inner spacer

The plan is to fit the new bearings and then use the YZ spacers (20mm long) and I'll get myself a handful of 0.5, 1 and 1.5mm thick M20 washers and space this up for real before I source a one piece spacer



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Cool. Only takes something to be a little different. But easy to check. Even after all if by some chance, the spacers ended up being too long, once they are made its super easy to drop them back to the lathe guy and say xxmm off this please. If they're too short its make them again.

That said I made mine so they had the grooves so the seals retain them like std.

So my Braking oversize disc adapter (POW106) has turned up and it doesn't fit!

The POW106 is for 2007+ YZ250F's so after a bit of back and forth with the guy I sourced the forks from, I checked the VIN number of the donor bike and guess what, it's a 2006

So, 2006 YZ250F SSS forks, and I now have forks with a 35mm lug offset which would have gone well with the GG geometry and triple clamps. Not that it matters right now as I'm using YZ triples, but it may be handy if I keep these forks for a future bike.

For future reference, the Braking web site lists the physical measurements for each of these adapters, and confirms that the POW13 will fit fork lugs with 102mm spacing between caliper bolts.

Pow13
To fit fork lugs with 102mm spacing
http://www.braking.com/catalogue/det...articolo=POW13

Pow106
To fit fork lugs with 77mm spacing
http://www.braking.com/catalogue/det...rticolo=POW106

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I've finally made some more progress with this.

I now have the following bits and pieces which will allow me to work out my axle spacers:
- the correct oversize disc adapter (Braking POW13)
- AllBalls wheel bearings from 99-03 Gas Gas ec300
- also Allballs Head stem bearings for YZF triples(top bearing Part Number 99-3513-5 . bottom bearing Part Number 99-3521-5)

Removed the original caliper hanger from the GG caliper and replaced it with the Braking one, and bolted it up to the SSS's. I've also completely removed the cable for the trailtech, and I'll work out if I tap a hole for that in the new caliper later on... bigger fish to fry right now.

Removed the old wheel bearing on the brake disc side of the front wheel, removed the inner spacer (I'll put it back in later on when I remove the old bearing from the other side), and inserted the "new" (wider) 99-03 bearing which has the correct ID for the YZF axle.

So now I have a GG front wheel with no inner spacer, original bearings in the RHS and 99-03 bearings on the LHS.What I need now is to work out the lengths of the LHS, RHS and middle spacers to fit the 99-03 bearings, and correct alignment between brake disc and caliper.

My original calculations were that 23.5mm spacers would work on each side to center the wheel, but that was without testing the brake caliper/disc alignment

The new inner spacer is easy as its the same length as the original one (66mm), but 20mm ID for the Yamaha axle

As I'm still waiting for a fresh inner spacer, I've just inserted the 99-03 bearing on the brake side, and will use the old bearings on the RHS + 3mm of washers to mimic the 99-03 bearing on that side.

I've reassembled this arrangement with the original YZF spacers on the RHS (24mm long) + 3.0mm of washers (to mimic the wider bearings - as above) , and the original YZF spacers on the LHS (20mm long) + 3.5mm of washers

Thankfully this looks to be trueing up nicely with the brake caliper, but I'm only getting a few threads on the axle nut, so I'm settling on the following:

- 23.5mm spacer on LHS (disc)
- 23.5mm spacer on RHS but I've also got the stock 20.0mm spacer that I'll try once I have all final bearings and spacers in as it should give me access to more axle thread.

I haven't checked if the wheel is exactly centered again yet with this setup but it "looks" OK

So while I'm waiting for a helpful mate from another forum to make me up some spacers, I'll fit the yamaha triples and fresh headstem bearings and work out what I do with the trailtech mount on the triples

Also procrastinating on whether I ride test these forks first, or while I'm waiting for the spacers I just send them off for a service, springs for my weight (if needed) and whatever "offroad" valving spec my tuner suggests...

It's strange how do things become blindingly obvious when you write it down

Looks like once I get the 99-03 bearings in (which are 3mm wider) I can just use the stock Yamaha 20mm and 24mm spacers, but just swap sides!!

The 24mm spacer will move the disc 0.5mm off the centre of the brake caliper, so I could perhaps live with it (I assume the pads would just wear accordingly), add a 0.5mm washer to the caliper bracket to move it, or I'm sure I could maybe manually shave 0.5mm off the aluminium spacer by rotating it over emery paper on a flat surface or something and still keep it
square.

Funny how you over think and overlook things when it's a long build


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Nice work mate! Glad to see the project progressing!