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TRX 450 sputters and backfires when i get on the throttle... HELP

23791 Views 32 Replies 7 Participants Last post by  FOXRIDER3361
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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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?
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?
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?
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
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.
im still not seeing any other screws
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?
yes, the engine sat for about 90 minutes before i checked the clearances
if i went down on the needle it would only get worse. it started off on the bottom setting of the needle and it got better when i went up.

I was getting a strong spark. is the accelerator pump part of the carb?
i just researched the accelerator pump. if it went bad, what part would haveto be replaced?
i have already tried 2 tanks of gas. it seems too consistent to be bad fuel if that makes any sense.
my diaphram does have some rust on the steel part of it, the rubber seems in good condition
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