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Bogging and backfiring/popping

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Not too long ago I purchased an 06 CRF450X. It has been kept in immaculate condition and came with a few upgrades including a big bore kit (not sure which one) and exhaust. I have only put a few hundred miles on it so far. When I first got it, the thing ran like a top, great throttle response and plenty of power. However, I went riding last weekend and in the later half of the day I noticed that when I was in the bottom end or standing still and pinned it, it would bog pretty bad and then I noticed that coming off of the throttle from high in the RPM range it would pop pretty bad, seemingly more than it used to. I have read some threads that talked about jetting and the accel pump but this seems odd that it would just develop that fast. I have a race coming up this sunday I would like to get it to a point where it doesn't do that if possible. As a side note, this is my first high performance four stroke so I'm still new to a few things about them. Any help would be greatly appreciated, thank you.

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buy a new pilot jet. get two. OEM size and one larger. Mine got much better with one larger. 

This is good for confirming pilot jet. May want to richen the needle too but as was said make sure all circuits are clean, float is correct height, and needle valve is in good shape too. 

 

Edited by shrubitup
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27 minutes ago, shrubitup said:

buy a new pilot jet. get two. OEM size and one larger. Mine got much better with one larger. 

This is good for confirming pilot jet. May want to richen the needle too but as was said make sure all circuits are clean, float is correct height, and needle valve is in good shape too. 

 

I will be servicing it tomorrow so i'll make sure to clean up the carb and the circuits.

 

Will having the big bore kit matter on jet size?

 

Also, I have yet to check the valves, could this be lending to the problem at all?

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I will be servicing it tomorrow so i'll make sure to clean up the carb and the circuits.



 



Will having the big bore kit matter on jet size?



 



Also, I have yet to check the valves, could this be lending to the problem at all?


Yes. Mine is 470 with bbk and then added was a stroker crank making 500. Likely reason it likes the bigger pilot jet.

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Possibly a deteriorating accelerator pump diaphragm. 

This happened to me, but I can't be sure of the symptoms. 

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Well just to follow up,  today as I worked on it I found that my header was a little loose which I believe was causing the popping,  also I took apart the smog pump and found that the previous owner plugged one of the holes,  so I plugged the other two, the popping is all but gone now. As far as the bogging goes,  I did the hot start trick and found that my fuel screw was a little off,  I adjusted that and the bogging only happens on the stand now. I think I'm ready for race day tomorrow! 

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