Heres a translation i got for that
Greetings from Finland! I bought a Yamaha Warrior for repair, and there is a problem. After warming up, it no longer runs properly. When cold, it works great. The engine control unit measured 74 degrees Celsius with an infrared meter after 3 minutes of use. Sometimes misfires and sometimes the injectors stay open. Does anyone have a similar experience? Is there a fault in the engine control unit or should I check the wiring harness?

 

Just ran into similar issue myself and I had to adjust the tps. Ymmv

 

Well since you just bought the bike what have you checked?
What does it idle at when warm?
Post as much info as you can

 

I reccomend to start with self diagnostic. Meyby you find something from there. Also seems like a TPS problem.

 

I took the bike to the repair shop as soon as I bought it, they couldn't find the problem. But the mechanic suspected the ECU.

Sometimes the spark disappears and sometimes the injectors stay open, these are when the bike is warm.
Idling when cold is normal

 

week ago one guy in Estonia had same problem. Her problem was coils. One coil was half dead. All the story was just as same like you.

 

the coils have been replaced with new ones

 

I did not know that, but would look at Diag. codes for sure.

 

Yeah in my case I had no codes,now I didnt use a multimeter to adjust my tps, I went in diagnostic mode tps was at 15 closed and 91 WOT, while still in this mode I loosend rotated clockwise slightly till it read 24 and 96.

 

I wonder if the ais is still on and working?