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Hey you all! I've been having a love hate relationship with a black Honda CBR 250R (2013) for 2-3 years now and need any help that i can get to fix it!

Got it from second owner when on 12 500 km and it was running perfectly for a month and so. After that it started losing revs when idle (it will jump up and down between 1.1k -1.4 k revs and eventually stall). It also loses acceleration power (feeling like lagging behind throttle) in the range 2k - 4k revs. When i go above 4k revs it runs perfectly. Idle rev problem persists when machine is warm after hours of riding. I changed the entire fuel injection block (with a second hand one - so can't know for sure replacement was good), spark plug, cleaned tank, fuel pump and piping, air filter and air ducts, and restarted ECU many times, but no change.

Problem deteriorated over time and now it will not hold ANY rev when idle. As soon as i let go of the throttle it stalls. I will work on it during winter to hopefully get a nice new season from spring on. Any ideas about where the problem / solution can be are going to be greatly appreciated since to me this is a mystery....

I am now working on the O2 sensor. Measured it the other day. When measuring voltage on warm engine it gives readings of 0.1v straight away and revolves around this level no matter how much throttle i give. So obviously it is malfunctioning and reading a lean fuel mix no matter how much throttle i give. My big question is - if sensor is giving lean fuel readings to the ECU, it should automatically raise revs until fuel mix reading is in the prescribed range, which is the opposite to what actually happens. So please share your thoughts here. I am ordering parts from the US, so i really prefer to get some diagnostics before jumping to buy just the next part to test if it might work.

CBR 250R Issues - YouTube

O2 sensor voltage measurement after 1min of engine working (v meter set at 2000mV) - YouTube

O2 sensor voltage measurement after 2min engine work (v meter set at 2000mV) - YouTube

O2 sensor voltage measurement at warm engine (v meter set at 2000mV) - YouTube

Thanks to you all. Safe ride and a lots of joy with your CBRs!
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