Yamaha XT250 Exhaust Uncork Mod by Ms Lil Mynx on 4Strokes.com
4Strokes.com Yamaha Technical: XT250 Exhaust Uncork By Ms
Here's how to uncork or derestrict the stock exhaust system of
a 2008 Yamaha XT250 for better performance. This modification, along with any
air intake mods, will help the engine breathe better. Here are the steps to
uncork the XT exhaust:
- Remove the screw from the bottom of the baffle and pull it out
of the muffler.
- Measure from the end of the muffler to the restrictor plate
inside. Mine was 7", so I went with a drill bit, that when chucked up,
was about 9" long.
- With either a drill bit or hole saw, drill a 1-1/2" hole
in the restrictor plate. The only drill bit I could find to fit my 1/2"
chuck was 3/4" so I had to do some additional reaming. The restrictor
plate is extremely tough so use caution when drilling. I left the muffler
on the bike because it was easier to work on, then removed it to shake out
the metal shavings. You can start the bike without the muffler and run it
for a few seconds to blow out any metal shavings that may have gotten up in
- Install the muffler and baffle back on the bike.
- After uncorking the exhaust, and/or air intake, you may also
want to richen up the idle mixture. With the exhaust uncorked, my XT runs
best with the idle mixture screw 2-1/2 turns out, which is exactly what Yamaha
recommends. However, after removing the factory plug (XT250
Mixture Screw Plug Removal), I found the idle mixture screw 2 turns out
from seated. This my have helped with emissions but caused a poor throttle
response and a longer warm-up time.
Credits: Yamaha related tech tip by Ms. Lil' Mynx. Edited and published
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2008 XT250 Exhaust
4Strokes.com Technical: Yamaha