LOSS OF POWER ON HILLS - RTO 125cc Full Size Adult Quad ATV

Question edited for clarity.
Question edited to English.
Question moved from Computers.

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Failing battery or faulty trickle charger or onboard charging system depending where the loss is. Your question loses detail in translation. See if you can find a Dutch forum.

https://www.google.com/search?q=Dutch+polaris+ATV+forum

Loss of power

https://www.google.com/search?q=polaris+sportsman+90+no+power

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not a car it is ATV offroad
same on all things like this that is a DC battery feed power loss
pure electrical failures.
fuses bad or loose?
battery is bad as it is intermittent and they do that.
so key on all power is lost, so a voltmeter in hand finds them all
if still dead testing
bad battery lugs and cable ends. loose or rusty.
the dash dead smacks of full power loss !

\and will be seen too in the fuse box, 12vdc lost there or even everywhere there dead. and bingo that. for sure.
learn to do the test fast only when dead dash.

if battery box fuses all then dead , so is the battery now.
batteries have many failure mode.
dead
or intermittent (hot ..,/cold or vibration )
or open cell 1 of 6 (2 volts per cell)
see 10volts there a cell is dead.!!!
12.6vdc is charged battery state, rested.
or jumper cable jump start the battery in ATV from car.
if dash wakes up bingo your ATV battery is bad.
buy the service manual for Kawasaki and see all that clearly

Check drive belt may be worn

your master cylinder,brake fluid,pads

Check fuses first, then check for broken wire with ohm meter to check for loss of continuity. Check port with ohm meter also.

It's hard to diagnose your problem , we need more info , , example , does your loss of power happen when going up hills , , low speeds , at full throttle, or in the midrange. I dont know the hours you have on it . Is there a lot of hours on the belt , is it fuel injected , or does it have a carburetor on it. Is your air filter clean , how long has it sat with the same gas in it . I can go on, and on, and guess all day , we need more info Bob. I look forward to your input in order to help with your issue.
A.J.

that was my first thought, belt is slipping or pully is polished smooth.

Its an automatic, so im guessing its belt driven. Possibly worn belt/pully's/clutch.

What is it be more specific yr make model

If you need further help, I’m available over the phone at https://www.6ya.com/expert/brandon_79b580f5a99c4386

Get it fixed, then turn it on.