The
Yamaha WR 426 F is one of the most sought after motorcycles in recent history. Folks had
deposits on the 2001 models without ever seeing one or even knowing someone that had
ridden one. In 1999 the WR's didn't land on showroom floors until late April and most of
them were sold. This 4-stroke motorcycle that's only been in production for two years has
been bestowed by many as the best production off-road motorcycle for under $6000.00. Is
there any way this bike could live up to such hype? Not a chance the way the WR is
delivered from the factory. After the first ride, riders are displeased, frustrated and
think they've wasted a ton of money on a timid trail bike. Rest assured you haven't pissed
away money but you do need to tinker with the WR to get the fire-breathing beast to emerge
from within.
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Get
some airflow:
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The stock air filter box
limits airflow to the filter. Remove the top lid from the air box to increase airflow to
the carburetor. This will make your WR a bit louder but it's a necessary modification for
cost free performance. |
Avoid
a heart attack:
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After break in the first oil
change is critical. Drain the oil remove the oil filter and inspect it for tears. (If
there are tears get a new filter.) You will probably notice tiny pieces of metal particles
captured in the oil filter. This is normal for the first few oil changes. Spray brake
cleaner on the filter to dislodge particles, then use compressed air to clean everything
off. Once it looks new again, reinstall it and go on with the oil change. |
Don't
cramp the big guy:
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Larger riders find themselves
cramped while sitting a top the WR. Applied Racing makes a top triple clamp mounting kit
that raises the bars up and moves them forward. This helps to make the WR feel a bit
roomier. |
| Hard times: |
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The stock seat on the
WR is too firm! CEET products make a seat that is about the same density but wider on top.
This gives your rear end a larger area to displace the weight. The first ride with the
CEET seat leaves one thinking it's too hard. On the second ride we noticed the CEET seat
was broken in and was more comfortable then the original saddle. CEET also makes a gripper
seat cover that keeps you from sliding around on the seat.
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WR time
to YZ time:
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The WR has been mellowed in
comparison to the YZ400F. You can change the timing to YZ 400 specs and increase the mid
rev punch and build RPM's quicker. Dave at the Southern California based Rick Peterson
Motorsports was kind of enough to help us out with this conversion. |
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Remove the seat and fuel tank. In the manual it says to remove the radiators, you don't
need to remove them. Instead remove the upper engine brackets. This will give you enough
room to slide the Cylinder head cover out. Now remove the Cylinder head cover. |
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Remove the
timing hole plugs and turn the engine until "I" is in the center of the small
plug hole. At Top Dead Center the cams will be facing away from each other. The exhaust
cams will have punch marks at 9:00, 12:00 and 3:00. The intake cam will have punch marks
at 9:00, 12:00 and 3:00. |
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Remove the cam
chain tensioner. Use a screwdriver to tighten the screw inside the tensioner until it
locks. Then in a criss cross pattern remove the cam chain tensioner. |
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Loosen the cam
cap bolts in a criss cross pattern and remove the cam cap. (There's a bearing retainer in
the cam cap, be sure not to drop it into the motor.) Turn the
exhaust cam one tooth clockwise. The timing mark on the exhaust cam will now be at 1:00.
Reinstall the cam caps and torque to 7.2-ft. lb., then reinstall the
cam chain tensioner and unlock it.
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Smells like exhaust:
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The stock
exhaust is quiet but restricts airflow and performance. You can remove the inner core to
achieve a better exhaust note and gain performance.
At the time of this write-up the California models were
not available but it's rumored the inner core can not be removed on these bikes. If your
comfortable with the power of the stock exhaust system, leave it on. If you need more
power an after market system is necessary.
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Mounting of the Big Gun exhaust on the WR400F requires four YZ400 tail pipe mounting
parts. The parts you need from the Yamaha dealer are 90387-0814J, 95024-08030, 90201-08310
and 5BE-14747-00. These parts attach the silencer to the frame. |
Our friends at Big Gun Exhaust supplied us with an exhaust system for the WR400. We used
Rick Peterson motorsports Dyno to test the Big Gun exhaust. As you see the Big Gun system
gives the WR more usable power throughout the power band. |
