Popping at 1/4 Throttle

[cavmat]

My 06 crf450x pops & farts at 1/4 throttle to the point where it wont drive the bike, idles perfect & once past 1/2 throttle blows a couple of puffs of black smoke then runs perfect but most singletrail riding is done at 1/4 trottle and its killing me.?

pilot jet 48

red jd needle 4th clip

165 main

idle 1 1/8 out

air box mod.

Valves are fine, carby has been dissasembled twice and jets cleaned, spark plug is black so I asume its running rich getting too much fuel then once past 1/2 throttle sends unburnt fuel out the back, bike has done 100 hours and never missed a beat, now this. Im stumped anyone help please.

Sick of trying to fix it, "just want to ride it".

[cubera]

Bad CDI?

[cavmat]

No, I run a vortex duel curve cdi, unplugged it and put honda one in still have problem.

[cubera]

Loose wire..ground?

[James_Dean]

My 06 crf450x pops & farts at 1/4 throttle to the point where it wont drive the bike, idles perfect & once past 1/2 throttle blows a couple of puffs of black smoke then runs perfect but most singletrail riding is done at 1/4 trottle and its killing me.?

pilot jet 48

red jd needle 4th clip

165 main

idle 1 1/8 out

air box mod.

Valves are fine, carby has been dissasembled twice and jets cleaned, spark plug is black so I asume its running rich getting too much fuel then once past 1/2 throttle sends unburnt fuel out the back, bike has done 100 hours and never missed a beat, now this. Im stumped anyone help please.

Sick of trying to fix it, "just want to ride it".

Did you remove the slide when disassembling the carburetor??

The thin plate that goes on the slide MUST have the square end installed downwards and the hole goes closer to the bottom. Popping and sputtering are common symptoms of having the part upside-down.

James

[Aussie CRFX Rider]

This is an amazing coincidence! - I finally got my bike going yesterday (its been out of action for 6 weeks with a blown gear box), i pulled the carby apart for cleaning and rejetting. I did exactly this! I put that plate in upside down! My symptoms were as described - popped and farted at low revs but good up top. Its easy to do, Bike runs heaps better now!!

[cavmat]

I havnt had the plate out but when I checked the needle it had exessive wear on it compared to a honda one out of an other bike with similar hours. all the multitapers were worn off and there are wear marks up the shaft of the needle. because this needle is brass and runs in the needle jet which is also brass could this cause more wear to the needle jet, an therefore alter your fuel air ratio and clip position, because the honda needle is alloy and is softer than brass it would wear first?.

[ewbish]

cavmat,

Popping and such at up to 1/4 circuit indicates to me a problem with your low speed fuel circuit.......since you have eleminated spark and the slide already.

My .02:

1. Really really really clean that pilot jet. Even a tiny grain of sand can cause those symptoms, hole that puppy up to the light and verify you can see through every opening and end to end. Also, clean the seat.

2. Remove your fuel air screw, verify it is assembled correctly, and the oring is in place. A broken oring, partially jammed up in front of the taper can cause the exact same thing.

I would suggest replacing the OEM with a zip ty or other after market brand to make it easier to adjust.