Engine dies above rpm 7500 also idling problem, YBR250

[modron]

Hello,

I have a bit of a problem with my Yamaha YBR250. Engine dies above rpm 7500-8000, at the beginning I thought it looses power but today I found out that it actually dies. First time it happened I shifted down to 4th and it went on again. I was 200km away from home so After the same thing happened 2-3 times i decided to ride slower (had some idling problems at the end too) and the next day I took her to my mechanic. I explained the problem and also told him that when I start it cold it idles at around 1000-1200 a bit lower then the manual says, after 10 min it goes down to around 800 and after 15-20min it stalls at every gear whenever Id let the revs drop so low (very annoying), he said that he needs to keep the bike overnight and ride it to check. 4h later he called me and said that he thinks he fixed it but cant be sure about the high rpms cos there are no roads in the city to ride bike so fast. The idling was 1300-1500 (as in manual) when cold and 750 when hot (stalls occasionally). Few days later I went out to ride and at the first stretch the engine died at about rpm 8000. When engine died I puled the clutch and stopped the bike, when I tries to start it it wouldnt. I had to turn the ignition key to off and on again to start. I took it back to the mechanic and he fiddled with it for few hours then he said it should be fine. He also told me its because I ride it too much, meaning too long in one day. I cant see how this is relevant, I usually stop every 1,5-2h for a short 10 min brake.

Today I took it out and everything was fine for first 3-4 hours (apart from idling- still ok when cold and much lower when hot) after the problem came back. It seems like the EFI cuts off fuel at high revs...but its just my guess. Im not sure if the mechanic tells me the truth cos the bike is still on warranty for next 2 months and if EFI is broken they will have to replace it

Do you guys have any idea what this might be

greets