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Discussion Starter #1
i have a 2007 yfz450 witha gytr slip on pipe and running the airbox lid off with a spectre high airflow filter. We have checked litterally everything and tried everything on this bike to no prevail.
main #162
pilot #42
clip 4th position

We have tried every jetting combo with no luck. Please help and dont be afraid to speak up or ask questions. Thanks
 

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I would up the pilot to a 45. You could try going a 1/2 turn more out on your fuel screw first to see if it helps. Do you know what needle you have? Ncvq?
 

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Discussion Starter #5
I have tried a 45 pilot before with no affect. Also I have an R&D flex jet to help adjust the fuel screw, but the fuel screw has very minimal affect on the idle speed and running of the engine. The honestly don't know the needle brand. It has 7 positions and is in the 5th position actually not 4th out of the 7 total positions. The backfiring/pooping always happens right before the engine hits idle speed after I blip the throttle or get on it big time. Also could this just be a problem of not having a spark arrestor? Just a dumb thought considering I have tried everything else.
 

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I have 2004 yfz sea level ncvq 4th 172m 48p screw at 2 1/2 no lid with foam aftermarket yoshi rs2 full exhaust FINALLY got rid of the popping at first I thought it was leaks in the mid pipe cause I can feel it leaking putting my hand around it on cold start up but popping is LEAN....... rich will feel more like a false rev limter with minimal popping
p.s. my air needle does little if any thing also (to big of pilot) but popping is gone im happy
 

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Try a 168-70 Also from hitting big jumps repetitively or just years of ruff riding your float doesnt let the bowl fill ALL the way up you have to bend small metal tang on float until its perfect every carb I rebuild the float is always out of adjustment take carb off and bowl.......with fuel line attached blow with your mouth air in carb through fuel line. Air should slowly get cut off as float is pushed from hanging to level with bottom of float bowl mounting surface you should not beable to blow air through as soon as it is level
 

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If air is cut off early (bowl half full) you have to play with little metal tang until its perfect .......when I would run it hard I would notice it would start popping after being on it for any length of time
 

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Run it and while on the throttle (in neutral), pull the choke. I'd bet it gets better. You sound very lean to me. I would say a 175 should be somewhere in the right area on your main. With similar mods to yours, I was at a 45 pilot and 172-175 main with the clip at 3 and the air screw 2 turns out. I'm at 3rd clip, 2 turns on the air screw, a 52 pilot and 205 main with current mods to give you an idea on how fat you can get with not a lot.
 

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Discussion Starter #12
i have tried a 45 pilot and 170 main with no effect. And when i pull the choke it immediately kills it. Ive never even used the choke with a cold start. I will check the float as soon as i can but im a little confused how that could cause it. But thanks so much for the replies you guys have no idea how frustrating this is.
 

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What's it do when your riding? you can't really check in neutral.
Have you tried 3rd clip on the needle?
What's your elevation?
 
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Discussion Starter #15
It dosnt pop that much when riding but just enough to annoy the hell out of me! Mainly if i just blip the throttle or really hammer it. Yes i have tried 3-5 clip positions and my elevation is 950ft.
 

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I would think - 45p 165-168m 3rd clip and around 2 out on the screw would be real close.
No leaks at the boots for sure? Hows the exhaust gasket at the head?
 

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Discussion Starter #17
i have tried that exact setup with still popping and flames. Dumb question though. How do i check if i have any leaks?
 

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i have tried that exact setup with still popping and flames. Dumb question though. How do i check if i have any leaks?
Spray some ether around the boots while it's running. If it idles up on it's own, it's sucking air from somewhere... just a quick way to check.
 

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Has the carb been recently disassembled?
 
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