2014 backfire and missing then running fine

I have a 2014 YZ 450. Was racing this weekend and when first started the bike would miss and flutter then usually clear out similiar to a two stroke when first started. As the day went it started doing this more and would not idle when doing this. I could turn the engine off then restart it and would run great...was not very predictible on when it was going to act up. I eventually called it a day when I was on the track and was at approx. half throttle and the thing acted like it just ran out of gas. Coasted to the side of the track kicked it and bike started up and ran fine all the way back to the truck. Any thoughts or suggestions is greatly appreciated.


It sounds like it was fired and wanted to go home!

Did you try changing the plug?

When was the last top end?

When was the last top end?


On a '14?  Really?


Get access to a tuner or a tech's system scanner and see if there are any stored codes.  Also check for any corrosion or such at all of the connectors.  And do check the spark plug.

Getting a tuner today to check for codes this evening. Will also check the plug. The plug did not seem relevent to the problem with it being intermittent. I am also going to double check the connectors again. Thanks for the help so far. I will post my findings.

Mine did the same thing.It was my gas boiling, bike comes too lean and runs hot. I just send out my ecu to tokoy mods

Alright guys here is an update on my findings after connecting the tuner to my bike. When I initially connected the tuner it was dispaying fault code "14" which in my service manual indicates "Intake air pressure sensor: hose system malfunction (clogged or detached)". I could not locate a "hose" not sure what they are referring to. I did locate the sensor in the air box and cleaned it and checked the connection. started bike for 5 seconds to clear the code and code cleared to "0". Then I went to check the RPM with the tuner and while checking it the tuner started displaying fault code "13". "Intake air pressure sensor: open or short circuit detected". Indicates defective intake air pressure sensor. Service manual says to execute the diagnostic mode. (code No. 03) to use FI diagnostic tool which I do not have access to. My understanding of this indicates it re-writes the ECU, also indicates it could be faulty ECU. My plan as of now is to overnight a new sensor and see if that solves my problem. I will also give your problem much thought mikey38. Did you have a fault code dispaying? Any additional thoughts and suggestions is greatly appreciated.

Update: replaced the intake air pressure sensor and the bike continues to not run correctly. Started bike and cleared the code off the tuner then checked the bike with it running and now is showing code "14" again consistently. My next move is to order a new ECU today. Will hope to have a solution tomorrow as I will overnight the ECU in hopes to ride this weekend to make sure I have a fix before a trip to Muddy Creek next weekend.

The sensor in the air box is the intake TEMPERATURE sensor not the PRESSURE sensor. You say you never found the hose the manual refers to, are you sure you replaced correct part? The sensor and hose your trouble shooting points out is on the side of the throttle body. How many hours are on the bike? Was there any sort of "Event" leading up to your current problem? Check that sensor and it's hose and let us know. Good luck :-)

Edited by drtrcr400

I see my mistake on the different sensors. Thanks a bunch drtrcr400. This may help me out on finding my problem. I did not pay close enough attention to the sensors.

Did you ever find the problem on this one?

Update: Problem was solved. It was the Intake "Pressure" Sensor. Replaced sensor and bike is running great now. Thanks to all for the help.

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