Question about 2000 Yamaha WR 400 F

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I have a 2003 yamaha big bear and it starts but backfires and sputers. We adjusted the valves and cleaned the carb and the problem stoped but then did the same thing.

Runs horrible but starts

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I would change the spark plug this is probably not the problem but I have had them look alright but give me some of the same issues. To me it sounds like a carb issue. If it starts and idles but won't run good at higher rpm's then it could be the main jet getting clogged or the float bowl sticking and not letting enough fuel in. You may need to add a fuel filter to the line. You may want to check your timing also.

Posted on Mar 23, 2014

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Posted on Jan 02, 2017

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SOURCE: 2003 yzf450 wont run right?

recheck pilot jet & pilot circuit.also check compression

Posted on Feb 16, 2009

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SOURCE: How do I adjust the valves on my 2003 Yamaha Warrior YFM 350X?

first you need to remove everything that covers your valve covers(gas tank etc.) remove the intake valve cover,and the rotor nut and timing plug.set the engine a t.d.c.(top dead center)fit a socket onto the rotor nut and turn it counterclockwise until the"I" mark appears align it with the index mark in the timing hole.use a flat feeler gauge between the top of the valve and the adjuster.loosen the locknut and turn the adjuster just until you feel resistance on the feeler guage.hold the adjuster and tighten the lock nut down.i can not tell you the min.clearance spec to your quad since i have a 660 raptor.try using the smallest clearance number.

Posted on Apr 25, 2009

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SOURCE: Cleaning Carb Jets

not to a trained ear also go by rpm and spark plug color

NOTE: use copper wire to clean jets, sync is just thottles are same position as all carb's just leave them adjustments alone will be fine if are out use a 1/8 drill an place in between piston/butterfly to carb bore to sync/calibrate

better use a manometer for adjusting screws

depends on condition of org parts

worn = richer running

new = lean an clean

also if changed the exhaust system need to
re-calibrate carbs for max performance

Posted on May 09, 2009

co7196
  • 3433 Answers

SOURCE: no front brakes on 95 yamaha big bear atv

gravity bleed. make sure fluid is always full. crack open the bleeder screw and let the brake fluid drip until no bubbles. Then close bleeder top off fluid and replace cap. Now, pull the brake handle. If there is no pressure or has bleed down, the master cylinder is kaput.

Posted on Jun 20, 2009

  • 19 Answers

SOURCE: yamaha big bear 400 will

Sounds like a problem with the starter, could be a starter fuse, relay or solenoid. The start cicuit wiring could also be damaged. If you can pull-start the motor, and it runs fine, you have pretty much eliminated any problems with the motor. Check the wires running from the start button make sure they are intact, also trace them and look for around a 1" cubed black box. This is the relay, when you push the button, if its working, you will feel the box click. Also locate the starter and do the same thing. If you feel or hear the starter click, the solenoid is working. The battery voltage could also be too low to energize the starter motor. Could also be a battery or alternator issue. Check the battery voltage and for any sounds coming from the bike when you push the start button.

Posted on Aug 21, 2009

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