Keep it in the family, DRZ250 Cartridge forks onto a DR650

It's been done before, but no seems to have ever documented it. Seeing as I am doing it now here's my experience, with pics even.

The DRZ 250 uses 43mm Cartridge forks with adjustable damping and rebound that outwardly look very similar to the DR650's Damper rod units, so I purchased a pair taken from an '02 model DRZ 250 off Trade Me (our local version of Ebay).

As these share the 43mm measurement with the DR 650 the 250 forks slide straight into the DR650 clamps and in fact use the same axle, spacer, speedo drive and caliper as the 650.

The one main difference is that the DRZ250 uses a 250mm disc and the DR650 290mm, plus the disc offset is approx 1-2mm different. This means you need either the 250 wheel and disc or to get an adapter bracket made up which spaces the caliper out 20mm and makes up for the extra 1-2mm offset to take the 650 wheel and disc.

I decided to go this route because:

Ease of fitment:
The 250 forks are the same size as the 650 forks though are a little longer so as already mentioned they slot straight into the stock 650 clamps/wheel etc. Being that they are the same size they are obviously up to the job structurally. The 250 springs do need changing to suit the heavier weight but the stock 650 springs aren't up to the job either so that is something that needed to be done anyway. More than likely you'd need to respring any other forks you got, for example the RM-Z 450 weighs ~112kg vrs the ~147 of the DR650 (both dry) so the 450 forks would be further out than the 250 ones.

Cost and availability:
You only need the 250 fork legs and a caliper bracket. In NZ this is a far cheaper option than buying say a complete DRZ-400 front end including wheel, disc, clamps, headlight mounting brackets etc etc, or buying a complete front end off something not Suzuki and having to make all sorts of steering head adapters, pressing out stems, making new ignition barrel and speedo brackets or whatever to make it fit. Suzuki 450 front ends rarely come up for sale here and when they do sellers want their weight in gold for them.

Impact on future mods:
I'm intending to do an outback Australia trip on this bike next year for which I'm intending to fit a Safari 30 ltr tank to cope with the huge distances involved. If you go much wider than the stock clamps you can get steering lock issues where the clamps hit the Safari tank. So you can loose some maneuverability at full lock, and potentially have to remake your steering stops to stop the safari tank being damaged in a crash.

I only bought the forks and am using the DR650 wheel and disc so a visit to my local friendly engineer resulted in this...


With a brake caliper bracket fitted and everything lined up I fitted the forks to the bike for about 500km on the road to see how they behaved. Overall they are a bit soft on the road spring wise as expected but seemed to have less brake dive.

Depending on who you believe the stock 250 springs measure at .37-.39 vrs .40 stock for the 650. While the 250 springs were softer than the 650 ones I did like the action of the forks. I didn't do anything with the valving due to the soft springs but it seemed to be a nice ride.

I swapped the stock 650 forks back on the bike so that I can open up the DRZ250 forks and try fitting some new springs.
While I had the 650 forks off the bike I removed the Intiminators I had fitted and refilled the stock forks with 15 weight oil to see what that did. My advice, don't do this. It makes the fork action horribly Jarry over even small bumps on the seal.

Here's the 650 forks and the 250 forks side by side, 650 forks in the center, 250 forks on the outside. Aside from the height, which isn't much, you can see differences in the caliper mount.

Digging around on the internet indicates the DRZ 250 springs are somewhere around 40mm shorter than the 650 springs. Further research indicated the Eibach .47 650 springs are about 10mm longer than the 250 springs, as both are a 43 stauncion the springs are the same diameter.

No one seems to advertise springs for the DRZ 250 so I decided the bite the bullet and go for the .47 Eibachs for the DR650 from Procycle figuring at worst I will end up with 10mm of preload from the slightly longer springs.

Disassembling the DRZ250 Cartridge forks.

Undo the bolt in the bottom of the forks which also houses the adjuster.
Once that is removed you can unscrew the fork cap and remove the cartridge which will leave you with this.

At the top of the unit the rod screws into the fork cap. The rod requires a 14mm spanner and the fork cap a 16mm.



Undoing those leaves you with the fork cap and adjuster rod



I've removed the spring here as well.

nice wee project eddie

I laid the stock DRZ250 and the Eibach .47 DR650 spring out next to each other, Eibach .47 for the DR650 on top, Stock DRZ250 at the bottom. You can't tell from this pic but the left hand ends are lined up evenly.



It turns out 2mm is all the difference!

Reversing all the disassembly steps resulted in a DR650 .47 Eibach fitted to a DRZ250 cartridge.

Looks like a great mod, Eddie!

Trading forks is usually a good thing,DR forks are pretty basic. I would guess a DRZ250 fork is about the same as a DRZ400 cartridge fork. I had a DRZe 400 and tried to make the forks work decently,they are harsh on rocks and dive even with stiffer springs/revalving,they dont seem like real great forks.
I think the cartridge emulator/resprung stock forks on my DR650 work pretty darn good after playing with them a little.
Is it really worth the trouble to swap forks over?

I'll find out whether it was worth it when they are all back together and have been on the bike for a while.
At this stage the caliper bracket is the only thing I've done thats any more trouble than doing springs and emulators in the stock forks, and fitting emulators requires full disassembly of the stock forks and drilling holes in them doesn't it? and if you don't like that you're stuck with damper rods with large holes in them.

If in the end I don't like it I can swap the .47 springs into my stock forks and re sell the DRZ250 forks, potentially with the caliper bracket for another 650 rider to try them and I'm not hugely out of pocket.

The stock DRZ-250 spring pictured above looks like it is progressively wound, while the Eibach spring looks to have a uniform spring rate. Any comments on how moving from progressive to uniform affects the handling in the DR-650 application? (I'm assuming that the stock DR-650 is a uniform spring rate. Can anyone confirm this?)

Stock DR650 springs are progressively wound.

indeed and rated at .40.
i think the drz250 springs are .37/.38
i use .47 on my 650 and weight 175lb. that rate is ideal for me.
.50 are good for 200lbs and .55 for the big boys.
http://www.procycle.us/bikepages/dr650.html#suspension

Bugger, I went to strip down the 2nd fork leg tonight and the screw and cartridge are just spinning so I can't get it undone.

I guess next step is to take it into somewhere with a rattle gun and get them to try it, any other suggestions?

there is probably a holding tool to keep the cartridge unit from spinning.
hit the nut with an air gun and it will spin faster than the internals and come off.

Come off as in undo, or come off as in shear?

Impact driver.
Cock the cartridge to the side to create a little extra friction on the inside bits.
Put the spring and fork cap back on to hold the cartridge for you.
Use jerky movements on the spanner/socket to simulate the impact driver.

This is a good mod for the DR350 also. 1994 and later DR350 wheels will bolt right up, the brake caliper is a bit different on the 94-97 models but it may fit and the brake rotor diameter is the same size.

I have a 99 DR350 and a 2001 DRZ250 and have verified it on mine. I have a 1991 spare wheel, I needed to change the bearings and center spacer in it to fit my 99 or the DRZ250.