wheres the pilot jet

5 replies to this topic
  • Mark_UK

Posted August 02, 2002 - 01:33 PM


ok,,,i have a 98 yz just reduced the squirt from 3 seconds to <.5 seconds
now it pops and bangs when i shut the throttle off.
i assume this is the result of the pilot jet being to weak?
ive turned the fuel screw out a full turn and it now sits at about 2 1/4 turns out.
so my question is
where on the carb will i find the pilot jet?
how much of a jump should i make in jet size.?
also should i raise the needle at all?

the bike runs hot at low revs [ again i assume this is a pilot jet issue?]

thanks in advance

  • Yak

Posted August 02, 2002 - 01:45 PM


On the bottom of the carb, undo that 17mm plug, its recessed in a hole about 3/4 inch up directly next to the main jet. The main jet is a 6mm hex, the pilot requires a skinny flat head screwdriver.

  • Boit

Posted August 02, 2002 - 07:17 PM


Yak; I think the 400's have a bottom plug that requires a 14mm wrench. Keihin wsied up on later years and put the 17mm plug for easier access.

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  • Guest_mxrider426_*

Posted August 02, 2002 - 08:00 PM


Why did you make the ap squirt so little? When you change your jetting, you should only go one size at a time. All the symtoms you describe are from a lean pilot. I don't think you need to mess with the needle.

  • Shawn_Mc

Posted August 03, 2002 - 12:07 PM


Changing the pump squirt should not cause the condition you describe. While your correct in your diagnosis, Im betting you have a piece of something in the pilot jet, and just need to clean it out.

The pilot screw range is between 3/4 and 2 full turns out. If you cant get it right in that range, you should change out the pilot.
But I doubt that you should have to change it now. Unless you changed something else too.

  • Mark_UK

Posted August 03, 2002 - 08:58 PM


what throttle opening range does the pilot jet effect?

all i know is it was squirting a hell of a lot of neat fuel in for a long time, surely this kinda fuel flooding would mask any week jetting??

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