WR426 mods same for YZ400F?

Do you think the airbox and exhaust mod will work on the YZ400F or other bikes in this same family? I don't believe my YZ400F has a throttle stop, right?


Yamaha built an excellent woods-capable machine right out of the box. Well, almost right out of the box, because the WR needs a few tweaks. In stock trim the bike is super quiet, but its power production is a huge disappointment because of the noise-restrictive parts placed strategically throughout the bike. This means that it is necessary to undergo some light modifications prior to heading for the hills. Removing the air box lid lets the thumper inhale, and extracting the restrictive plug in the end of the silencer frees up the back end.

In stock condition, the WR also has a throttle stop located at the base of the Keihin carb that only allows about half a full pull of the throttle cable. Since Yamaha offers the WR as an EPA-compliant machine, it has to meet some strict noise requirements which facilitate the need to implement those restrictions. But for best results, remove the stop and fill that orifice with a blob of silicone. Once you make these minor modifications the WR is ready to get it on. But be advised: the changes we mention here are only recommended for closed-course racing, okay.

Once the engine is freed up, it makes a ton of low-end grunt and midrange muscle. Deserts tremble at the pulsating exhaust note of the big 426cc engine as it accelerates to redline before disappearing into a distant horizon. Forests echo and quake with the resonating sound as hill climbs and single track are consumed with a twist of the wrist. Yes, dear readers, we thoroughly enjoyed riding the dirt-eating monster that is the WR426

Whats the exhaust mod?

Check out this link to http://www.thumperfaq.com/ The mods will also work on the YZ400F and YZ426F Do a search for the mod you are looking to do here at TT and you should be able to find all the info you need.

There is no "lid" on the YZFs airbox, but the other mods will work.

The exhaust mod for the WR is to make it like the YZFs - done already and no the YZFs do not have a throttle stop.

Thanks Dano. :cry:

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