Crf450x fcr carb popping help ?

When you give the bike a constance rpm it kinda sounds like rev limiter no back fires just like poping

It's probably the Throttle Position Sensor. Very common issue. Ignition is hunting between 2 maps. Mx bikes hate constant throttle.

You may also have a worn needle jet. Leaks a bit of extra fuel past needle to give a slightly rich condition at mid throttle.

How could a fix the throttle position sensor because i have had the carb apart and the needle didn't seem to be i think its the throttle position sensor

Make sure it's set correctly.

Can be tested with multimeter and adjusted by loosening screws and twisting left/right. Look in service manual for specs.

The hole the needle goes into (needle jet) not just needle (jet needle) can be worn.

Try jetting slightly leaner on needle.

Move clip up 1 spot.


But a vortex ignition. This has been reported as best fix for TPS stutter.

^^ wrong


Honda does not use ' switchable maps' in their ECU's. They are 3-axis progressive.

That's the old Yamah method of mapping


Do not mess with the TPS, as it is not going to change anything.


You have dirt or corrision in your carb, or an air leak (more likely) at the hot start plunger or fuel screw oring.


You MUST adjust your fuel screw for changes in air density, which means possibly every ride.


Time to do a full carb service if adjustment of the fuel screw does not do it.


Search " fuel screw" in the 450X section


Glad Kaa Corrected that.

I was talking from Yamaha experience.

Shouldn't make assumptions about other manufacturers!!

As he said. Get fuel screw / pilot set right and work from there.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now