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Discussion Starter · #1 ·
I have an '06 trx 450 ER. I took it out the other day and it ran fine for a couple of minutes, then it started to sputter and backfire out of the exhaust (shooting flames out of my HMF pipe) it feels like i lose a bunch of hp. So i replaced the spark plug, COMPLETELY took the carb apart and cleaned the sh*t out of it. I cleaned the air filter and its still doing the same thing. It starts up just fine and i can roll into the throttle and its not nearly as bad as when i hammer down on it. Can anyone help save my weekend of riding?!?!
 

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I'm stumped, you did everything I would have mentioned.
 

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Discussion Starter · #3 ·
back in september i had the top end redone. the mechanic put in new valves and a top end. i ran it a few times since then and it worked fine. Yesterday is when it started to mess up. i took it to the mechanic this morning and he thought it was something with the carb, but wouldnt get to it till tuesday. thats when i decided to clean it myself. could it be something with timing or valves out of adjustment?
 

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What size main jets are you running? if you are running with no breather box top you will need a 180 to 185 if you have a pipe on it and the air screw out 2 turns. sounds like its lean and do you have a adjustable needle in it if so 3rd notch from bottom, if not get one and in stall.
 

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Discussion Starter · #5 ·
i do have an aftermarket pipe, no air box lid and i do have an adjustable needle. the clip on the needle is at the very top. i will take the carb apart and change that setting and see what size my jet is. where is the air screw located?
 

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I bet moving the clip will solve your issues.
 

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Discussion Starter · #7 ·
i just took the carb apart. the clip was at the very bottom of the needle. now it is on the 3rd spot up. the main jet is 175, and the other jet says 48 on it. im not sure on where the air screw is located though, any help?
 

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I'm not real sure about the 450 carb, but on most carbs the pilot screw or the air screw is located on the bottom, toward the front of the carb.
 

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Discussion Starter · #9 ·
i just took it out for a run and it seems just a little bit better not much. i didnt mess with the air screw yet. the only screw i see is on the left side of the carb under the fuel line and when i unscrew it, fuell leaks out from one of the vent lines below it
 

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i just took it out for a run and it seems just a little bit better not much. i didnt mess with the air screw yet. the only screw i see is on the left side of the carb under the fuel line and when i unscrew it, fuell leaks out from one of the vent lines below it
That's probably the drain for the bowl.

Try looking at the same level as where the bowl meets the carb body. I'm thinking it's on the same side as the fuel line hooks to the carb, right on the corner of the carb.
 

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Discussion Starter · #11 ·
i just checked it again, i've looked this whole carb over and dont see any other screws except for the one that drains the bowl.
 

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Look at this drawing. It's the one labeled "pilot screw".

 

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You're stll not jetted right. the air/fuel screw only effects the idle. It won't do anything for your rpm range.

Try going to the next step up on the clip, see if that helps or makes it worse. You may need to go up on the pilot.
 

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You're stll not jetted right. the air/fuel screw only effects the idle. It won't do anything for your rpm range.

Try going to the next step up on the clip, see if that helps or makes it worse. You may need to go up on the pilot.
Yeah, I agree with Red. All the mixture screw is for is to get a smooth idle.
 

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I have an 07, I have never needed it but I have never found my mixture screw either. There is another cable that comes from where the throttle cable attaches. It is along the right side upper frame rail. It's a black knob.
 

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Discussion Starter · #17 ·
i found the air screw and turned it out 2 turns after i screwed it in completely. the black know mounted on the rail is the idler adjustment, mine is idling just fine. i had the needle set at 3 up from the bottom earlier then adjusted it to 4 up, it didnt really seem to make a difference. I just took the valve cover off and used a feeler gauge to check the valve clearance. from what i understand the intake valve clearance should be .006" (+/- .001") and an exhaust valve clearance of .011" (+/- .001").
My left exhaust valve is .012, my right exhaust valve is .016. My left intake valve is .006, and my right intake valve is .008. Could this have anything to do with my problem?
 

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Make sure your engine is cold when you check the valve clearance.
 

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I doubt that much difference in the valve clearance would matter as far as running. It might make the rockers tap a little.
 
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