A month ago while riding my '05 z400 hard, I stopped to refuel and then I wasnt able to start it. Finally bump started it but it ran like crap and stopped again like 2minutes after. I wasnt able to start it, neither by pushing it. Got back home ,cleaned the all the ground on the frame, changed the plug, cleaned my air filter, changed the oil and it ran fine for 2hours in the sand pit. then while coming home by the road it started to run like crap but it didnt stall. I opened the carb, inspected the jets and everythings , and the carb is as clean as a clean carb can be. Went for a trail ride, it ran for 5 minutes and stopped while slowing down to cross a road. Was able to bump start it once, ran like crap and stopped, exactly like the last time. Then it never started again. Came back home, plug was super white meaning it runs lean but usually my plug is a clean brown. Tried running another coil, didn't work, drained the tank and dropped new gas, didnt work. the petcock flow like new. It has sparks. Switch is good. Inspected all the wiring harness.I dont have a compression gauge, but the piston is only 2 years old and if the compression was super low I wouldn't be able to start it. Yesterday I've been able to ride it for 30 minutes before it stalled. It never takes the same time before it stalls. I always clean my airfilter after every ride and I change my oil every 15hours ( suzuki recommends every 6months) . I noticed yesterday that it was losing prestone. I refilled the rad and it got empty again. I've found no leak. Before it stalls, it always starts to backfire.
So, could my engine stall because it is burning prestone?
could it be a bad cdi? electrical wise, it is the last piece I have not tested ( because we can't)
Or any idea? I'm lost on this one
( english is not my main language, so if you dont understand something, tell me and I'll do my best to explain it)