exc 400 flat spot

[Grum]

Hi, I have a 2000 exc 400 and I am having trouble with a flat spot . l have fitted a jd jetting kit and lenghtened the throttle pump duration but l still have a hesitation when l first crack the throttle.If any one could give me any tips it would be great ,i,m thinking of drilling out the throttle pump jet in the venturie to give it more fuel any Ideas .Thanks Grum.

[bajadog]

Hey Grum,

Have you done any mods to the exhaust or the intake?

What does your spark plug look like?

[Grum]

Hi Bajadog, I have removed the muffler end cap and cut out the restrictor but the problem is worse now since l fitted the jd jetting kit . The plug looks ok it dosn,t blow black smoke as if it is to much fuel. I changed the throttle pump duration before i fitted the jet kit and it was good .It runs great with the jet kit more power etc, just this bog off idle has got me stumped.The jet kit came with a spacer to go over the bottom of the throttle pump diaphram which l fitted ,but i took it straight out and made it better but it still bogs .I was thinking of opening up the throttle pump jet . Two of my mates have 530 and 450 and their throttle response is great but if you crack mine open quick you can stall it. Any Ideas .Thanks Grum.

[Grum]

Hi Bajadog, I have removed the muffler end cap and cut out the restrictor but the problem is worse now since l fitted the jd jetting kit . The plug looks ok it dosn,t blow black smoke as if it is to much fuel. I changed the throttle pump duration before i fitted the jet kit and it was good .It runs great with the jet kit more power etc, just this bog off idle has got me stumped.The jet kit came with a spacer to go over the bottom of the throttle pump diaphram which l fitted ,but i took it straight out and made it better but it still bogs .I was thinking of opening up the throttle pump jet . Two of my mates have 530 and 450 and their throttle response is great but if you crack mine open quick you can stall it. Any Ideas .Thanks Grum.

[bajadog]

Just an idea.

Try leaving the air box cover off, and see if the bog
is still present.

I know when I went from a 38mm CV carbie to a 41mm FCR carb,
the air box was to restricted for the extra volume of air the new carbie
wanted.

[Grum]

Hi Bajadog, I,ve fixed my bog of idle. Today I pulled the carby off and played around with the accelerator pump .I changed the timing and gave it 4 seconds duration.I thought it may be a bit to rich but it worked great .I put it back to geather and richened up the mixture 1 turn out also. With this fixed and the jd jetting kit and muffler baffle removed now it flys . I need to set the suspention now and it will be great. Thanks for your advice. Now I wont have to burn it. Thanks Grum.

[bajadog]

Good to hear you fixed it Grum.

Go have fun now.