exhaust cough after engine turned off

I Have a stock 2004 wr 450 that when i shut off the motor it makes a cough (backfire sound)out the exhaust, i have removed restrictions on intake and exhaust and it breathes great,my head pipe tempeture is around 240. the bike run's great until i turn it off,seem's like it want's to have the last word (lol) any thought's wil be appreciated

My brother in law's stock 2008 wr450, uncorked and it almost always let's out a fart after you shut if off. Cracks me up every time. Brrrrrrrrrrr....... Poof

I Have a stock 2004 wr 450 that when i shut off the motor it makes a cough (backfire sound)out the exhaust, i have removed restrictions on intake and exhaust and it breathes great,my head pipe tempeture is around 240. the bike run's great until i turn it off,seem's like it want's to have the last word (lol) any thought's wil be appreciated

Stock, as in you opened up the intake and exhaust, but did not re-jet?

 

You are now extremely lean, and should re-jet.

 

Have you ever properly adjusted your fuel screw?

main jet 165,pilot jet 45,needle at #4groove, air screw is 2 3/4 out

My brother in law's stock 2008 wr450, uncorked and it almost always let's out a fart after you shut if off. Cracks me up every time. Brrrrrrrrrrr....... Poof

you think it's funny,but i bet your brother in law isn't laughing

main jet 165,pilot jet 45,needle at #4groove, air screw is 2 3/4 out

 

Why is your fuel screw at 2.75 turns out?

This is way too much.

You should be at 1.5

If you cannot obtain highest idle at approx 1.5 turns, you slide is too high: turn down the idle and try again.....or you have an air leak at the hot start or header or....

you think it's funny,but i bet your brother in law isn't laughing

Perhaps... He keeps saying he is going going to jet it properly... Eventually ^_^

Why is your fuel screw at 2.75 turns out?

This is way too much.

You should be at 1.5

If you cannot obtain highest idle at approx 1.5 turns, you slide is too high: turn down the idle and try again.....or you have an air leak at the hot start or header or....

could the big o-ring on the slide cause a problem,and how would you check for air leak at the hot start ?

could the big o-ring on the slide cause a problem,and how would you check for air leak at the hot start ?

There is a soft-seal on the slide plate, but that would not be an issue here. That usually shows up under acceleration as a lean condition.

The hot start has a plastic nut to hold the plunger cable in place. They brake and/or crack when you turn the carb sideways to get at the float bowl.

You should at least check the nut, pull the plunger, and inspect both for a good seal. And the fuel screw oring while you are at it.

Thank you Krannie sounds like you know the bike well,there is one thing i forgot to mention,when i purchased my bike it had some small dings in the head pipe,to protect the pipe i wrapped it in exhaust heat wrap,i don't know if this makes a difference ?

Thank you Krannie sounds like you know the bike well,there is one thing i forgot to mention,when i purchased my bike it had some small dings in the head pipe,to protect the pipe i wrapped it in exhaust heat wrap,i don't know if this makes a difference ?

Not an issue

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