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Discussion Starter · #1 ·
My 03 400ex is popping on decel I just put a DG slip on on it and that's when it started doing it . It has a 155 Main and a 42 pilot I have messed with the A/F screw and that doesn't help or make it worse it also has bigger piston. And Hot cam in it but that was already it it before the pipe went on . Can anyone please help I'm ready to go riding damn it...lol
 

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The popping is caused by the fuel mixture being too lean with the throttle closed. You can attack this problem several ways: in all cases be sure to use 93 to 95 octane fuel. The easiest fix can be to increase the idle speed or enrichen the fuel/air mixture by installing a 45 pilot jet and adjusting the fuel screw for the best idle or add some back pressure to the exhaust. In any case, the popping is not hurting anything. Go riding, just don't ride in dry leaves or grass due to the possibility of starting a fire by using an exhaust without a spark arrester.
 

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Discussion Starter · #4 ·
Well. I just took the carb off again and cleaned it and put a 152 main jet in it . I noticed that it only has a 38 pilot in it I thought it was a 42. But anyways it wouldn't start with the 152 in it unless I held the throttle down and I also noticed when I took the carb off there was gas in the rubber boot that goes to the motor side. So is that the pilot jet or the main jet
 

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Maybe this will help.
Auto part Vehicle
 

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First - I don't understand your post about "too much back pressure". Excessive back pressure will cause a loss of power as RPM increases, but it will not hurt the engine.

Second - you say you cleaned the carb and actually inspected the jets. How did you mistakenly identify a 38 pilot jet for a 42? Advice; it is unlikely you could ever make the engine idle correctly with a 42 pilot jet. You may increase the pilot jet to a 40 and with proper fuel screw adjustment get it idling as desired. The 152 main jet is two sizes over the standard 148 and should be adequate for the pipe change.

Third - the raw fuel in the intake has nothing to do with the size of the jets. It most likely indicates that the fuel level in the float bowl is too high. There are many other possibilities depending on the circumstances immediately preceeding the removal of the carb. Had the engine been running just prior to removal? Was the fuel shut off about 30 seconds before stopping the motor? What kind of fuel do you have in the system?

Learning to "tune" carbs takes time and tunning a carb is time consuming. Use new jets when rejetting the carb and make sure to use the proper style jet, not just jets that look the same. Never make more than one change at a time so if the change produces undesired results it can be easily changed back.

Good luck - you are going to need it until you understand what effect one change is going to have on other charactistics.
 

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Discussion Starter · #9 ·
It ran great before I put the new exhaust on it . I have been trying to get it right for 2 weeks now I'm just about over . Might just sell it and get another one . I do t see how a simple upgrade can be this much of a headache if I would have known that I wouldn't have wasted the money on it
 

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The problem is with 'the noise maker'. The bike with the DG pipe on flows too much air. Causing the bike to run LEAN. You proved that by re-installing the stock (tuned) pipe. (where it ran fine).
Now you get to re-jet your carb. You will spend another $50.00 in jetting and get it back to running where the stock (tuned for the bike) is at.
What will you have gained? Nothing. What will you have spent? LOT's! (Time and Money)
Sorry.
 
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