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The throttle stop on the WRF prevents the slide in the
carburetor from opening all the way (limits the throttle to 3/4 throttle).
While it exists on both the YZF and the WRF, the size of the stop is
smaller on the YZF. Most riders cut down the stock throttle stop to YZF
specs (see below). Others have replaced the original throttle stop with
the YZF throttle stop (Yamaha part number
5NL-14591-00-00). Many dealers will do this mod as part of the normal
setup of this bike. If you buy a new WR250F ask your dealer if they have
done this mod.
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Remove the throttle cable cover,
which is located on the right hand side of the bike, by removing a single hex
head bolt. To access this bolt you have to pull back a small rubber flap (tab)
on the throttle cable cap (Figure 1). (See Owner’s Manual page 4-19).
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The throttle stop screw is located
at the rear of the throttle "disk" assembly, and points almost vertically,
tilted slightly towards 1 o'clock as you view from the right side of the bike
(Figure 2).
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Using a 4mm hex head wrench,
preferably one with a ball head, back out the throttle stop screw. There is
Loctite on the threads so the initial going will be tough.
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The throttle stop screw measures
~1.30" (33mm) while the STEM only measures ~1.10" (28mm).
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The throttle stop should be cut to
a total length of 0.975" (24.765mm) or a stem length of 0.790" (20mm) in order
to match the YZF's full travel. Use a hacksaw or Dremel cut-off saw to make
the cut. Cut on the long side and then file to the final length, clean off any
burrs and provide a slight chamfer around the circumference (Figure 3).
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Coat the now-bright cut end of the
throttle stop with some light grease to guard against corrosion. Put
everything together, again using some Loctite on the throttle stop threads.
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Figure 1
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Figure 2
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Figure 3
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Click images to enlarge
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Update for 2003-2005 Model
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| The throttle stop must still be shortened on the 2003-2005 models. I have no
specific information but I assume the length of the stop after cutting is
unchanged from the previous years. The 03 does not have the rubber boot.
The screw is behind the plastic grey or metal cover. The stop is easier to access
if you remove the cover.
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ThunperTalk Archives (updated
by TT member Jurgen 12/10/04)
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Listed hear are what I consider the most helpful threads. There are more threads on this topic in the
ThumperTalk archives. To find them, search the
YZ250F/WR250F forum. Suggested keywords: throttle stop,
throttle limiter, throttle screw, free mods. |
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