Intermittent low rpm / idle problem

07 WR450 Have an intermittent issue with my bike. Generally runs fine then it goes into backfiring on deceleration towards the low rpm range, then it won't idle, just cuts out when you pull the clutch in.. I can turn the idle screw 1 1/2 turns and it will idle fine but still back fire. Then all of a sudden things change, the idle ramps up high and the backfiring stops. I turn the idle back down the 1 1/2 turns till it idles low again and it runs fine just like it should. It does not matter if it is at running temp or stone cold. Yesterday I road 20 miles just fine then acted up in last mile. Today it acted bad for the full 30 miles. I did change the plug, disconnected the fuel mixture sensor and neither helped. I'm putting in a new battery tomorrow because the conductivity is poor but it still puts out 12.8 v under a load. It is the original battery. Any ideas? 

Fuel mixture sensor ??? 


No such thing on your bike.


You might mean the TPS on the carb.....



You need to service your bike!


At  the very least:


- replace the pilot jet with a new one

- clear  the pasage above it with fishing line and spray cleaner

- get an R&D remote fuel screw and learn how to adjust it

- re pack your silencer

- tighten your header, or replace the crush washer

- clean polish and lube your hot start plunger, and probalby replace the cap on top, as it cracks and or leaks

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