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Discussion Starter · #1 ·
My 02 400ex has nothing aftermarket besides a big gun es exhaust just the slip on. I recently got my 400 back from the shop it sat for months there not started it wont start i cleaned the carb and set the jets to normal settings first if someone can get me all the jet specs like how many turns each one is supposed to be out and when i start the quad it does not idle and when you hit the gas its hard to explain but all the exhaust notes are straight backfires it will not run ive adjusted everything somebody just please help me

Super Moderator
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There's only 2 adjustments that can be made externally - idle speed and idle fuel

The idle speed screw is simply set for the desired idle speed (normally around 1400 rpm)

The initial setting on the fuel screw is 2 1/4 turns from lightly seated - with the engine fully warm (ride for about 10 to 15 minutes), then adjust the fuel screw for the smoothest idle

I would like to hear the full story; why did it sit at a shop for months? what was it at the shop for? why did it leave the shop not running? I can get you all the jet specs, but there is no adjustment to the jets other than replacing them with different sizes.

The full specs are:
Carb = Keihin
Carb ID = QB10A
Main Jet = (for altitudes up to 5000 ft - 148) (for altitudes of 3000 to 8000 ft - 142)
Pilot jet = 38
Needle jet clip position = 3rd groove from top
Float height = 18.5mm (.73 in)
Pilot screw = 2 1/4 turns out
Idle speed = 1300 to 1500 rpm
Throttle cable free play = 3 - 8mm (1/8 - 5/16 in)

In my opinion - it shouldn't have left the shop unless it was running right
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