Difference between a WR400 and YZ400F

Hey, new to all this, but so impressed with the site I've joined!

Buying a WR or YZ400. Have both available, '00 models, both road reg.

Apart from the wiring loom, what else is different from these two seemingly similar bikes?

PS Based in the UK, but would apprecite any comments as I'd imgine the specs are similar.

Many thanks guys

hope you can help

rob morphet

YZ vs WR where to begin....

Well wr stands for Wide Ratio (gearing) vs YZ

WR has all the electrical doodads to run lights etc. YZ dont.

Plastics are different

YZ has no coolant overflow

YZ engine tuned & jetted differently, but basically the same

YZ has stiffer suspension springs

YZ has smaller gas tank and more 'race ready' seating....you can get further forward on the seat on a YZ

Most parts are interchangeable, you can even YZ time a WR for some low end loss but high end stab !

Your choice would come down to what you will use it for...mostly track racing or dual sport/enduro.

Many people spend a lot of money trying to YZ their WR's and YZ sometimes try to WR theirs. The big difference at the end of the day is the YZ timing and the gear ratio. All can be changed relatively easily, except for the gear ratio which I understand can be done but at great expense.

For more stuff do a search


Superb, thanks

Its being used for Supermoto (racing) both on tarmac and shale (gravel/jumps etc)

I was worried about cush drives and balancer shaft (? - my old days from mx), and running a yz on road bais. If there's little difference then the wide ratio box would be better for the long straights!

any crafty mods?

thanks very much for your advice too


Neither has a cush drive, mechanically the two are almost identical, I will point out that US model YZs were 426 cc.s in 2000 model year but WR was still a 400...

Other than lighting coil/stator, jetting, exhaust, gear ratios and cam timing the bikes are mechanically identical. WR tank and seat is ergonomically retarded for serious riding, you can't get your weight forward. Most WR owners end up with a YZ-style tank and seat.

For SM I would think the close ratio YZ box is better but I don't really know....

If you are using the bike for Supermoto, you will definitely be better off with the YZ. It has a much lighter flywheel and will pull out of corners better on a track. The WR has a lot of stuff you don't need like a battery, lights, stator etc. Unless you are driving it on the road, the WR would be better since it is almost ready to go like it is :).

yeah, thats the compromise, 1 bike 3 uses (road, enduro and SM) so I think the WR may win on all round points.

We have a wet/damp climate here, and most of the SM comps (low key & easy!) are run on karting tracks so it rare if you get a sticky corner, what with the rain and polished rubber! so a short box may highlight just highlight how crap I really am at this sport;-)

Are there any easy mods i can do? jet & box maybe?

cheers again guys, really appreciate your help.

WR Mods

Do a search on the below topics to find what you need to know...theres a gazillion posts on each one.

- cut grey wire

- YZ throttle stop (A MUST if not done already)

- rejetting - JD Jetting recommended

- remove the air box cover

- bk mod (2000+) , de-octopus 1998 & 1999

- yz timing

- James now (free if you do this instead of Powernow

- raise forks 1/2 inch for slightly better turning

- what am I missing guys ??

Hey guys, thanks for the advice! They are all on jobs to do before the racing starts, really looking forward to this now!

question are:

- de-octopus 1998 & 1999. Mine WR4 '99, has the black box fitted, however also has a Hot start switch attached. What does this do? Quite happy to remove the octopus, but need to know why.

- James now (free if you do this instead of Powernow - no idea what this is, and couldn't find any threads on the subject.

Again, really pleased with the help you've given me.

Thanks very much

Rob Morphet

When searching make sur you choose a forum and extend the timescale of the search to cover a reasonable period of time.

James now: http://www.thumperfaq.com/jamesnow.htm

De Octopus :

Search wr400/Wr426/wr450 forum for deoctopus for all posts

I have a crossbreed of the two, the frame and suspension from a '99 WR400 and a '01 YZ426 motor & trans, with reg in California, and I love the piss out of it, I ride 40 to 50 miles a day.

with that in mind, I have YZ gearing, a final drive of 15T/44T far from stock, it will take most anything in short distances, around obstacles(sometimes over them)but it starts to hit the rev limiter at around 97 to 100MPH , at around 50MPH sportbikes will then catch back up and walk away in straight line. thats ok, hit a section of road construction and they can't keep up.

if you plan on daily riding than WR, if you plan on racing only than YZ

your gear box and electrical and your only real concerns(riding at night demands POWER)

I have a sealed lead acid in the air box with the K&N that helps power the H4 55/60watt light + the XM satellite radio in my tale bag

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