In cold weather the battery in my ATV discharges to where the starter can not function. There is about 300 hours on the machine, it receives excellent maintenance and it used every week. How many '[mas'[ does ths computer draw? This is a sportman x2 700 EFI

Put a new battery in it and add it to the price. ATV batteries are abused, they need a trickle charge if not used for a month. Expected life in a neglected state would be 3 to 4 years. Is it the original battery and 8 years old? Strip and clean the carburetor.

https://www.batteriesplus.com/battery/atv/yamaha/grizzly-300-automatic/300cc/2012

https://www.google.com/search?q=2012+yamaha+grizzly+300+clean+carburetor

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If your HS400ATV is not powering up even with a fully charged battery and you've already replaced the ignition switch, there may indeed be another module or component that could be causing the issue. Here are a few possibilities to consider:
1. Main Fuse: Check the main fuse for the ATV. It is typically located near the battery or within the fuse box. Ensure that the fuse is not blown and is making proper contact. A blown main fuse can prevent power from reaching the ignition switch and other electrical components.
2. Starter Solenoid: The starter solenoid is responsible for engaging the starter motor when you turn the ignition key. If the solenoid is faulty or not functioning correctly, it can prevent the ATV from powering up. Inspect the solenoid for any signs of damage or loose connections. Consider testing the solenoid or replacing it if necessary.
3. Kill Switch/Safety Interlock: Check if there is a kill switch or safety interlock feature on your ATV. These safety mechanisms are designed to prevent the ATV from starting under certain conditions, such as when the brakes are not engaged or if the ATV is not in neutral. Make sure these switches are in the correct position and functioning properly.
4. Wiring and Connectors: Inspect the wiring harness and connectors for any loose, damaged, or corroded connections. Pay close attention to the connections between the battery, ignition switch, and any other modules or components. Clean and tighten any loose connections, and repair or replace any damaged wiring or connectors.
5. Electronic Control Module (ECM): The ECM or other control modules could be a potential source of the issue. These modules control various electrical functions in the ATV. However, diagnosing and testing these modules often requires specialized tools and knowledge. It may be best to consult a professional ATV mechanic or an authorized dealer who can properly diagnose and test the modules if needed.
If you've checked these possibilities and the issue still persists, it is recommended to seek professional assistance. They will have the expertise and equipment necessary to diagnose and resolve electrical issues specific to your HS400ATV.

Have your batteries CCA checked.. (Cold Cranking Amps).. take it to a battery shop or autozone or Oreilly's.. they can check it..this is what makes your engine crank..NOT voltage.... and how do you know the starter is good?..

Sketer, check all fuses, could be the stator..also the regulator/rectifier faulty. Google search your make and model# manual.Check the attached links,instruction and guides, Good luck
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"ATV" service and repair manuals - CRXSi.Com

www.crxsi.com/reference/manuals/atv/
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See: https://www.youtube.com/watch?v=aDN5dylOFBw and http://xplorer-manual.blogspot.com/2014/11/download-polaris-xplorer-300-repair.html

Battery weak or starter going bad. Most likely battery.

power wire and ground make starter work inside starter case. the power wire goes through several safety switches on way to starter. check each connector 4 loose wiring. battery (-)to engine and frame need more history here b4 i can help anyymore. good luck

check battery u may need a jump or the oil is too cold and 4 wheeler needs to sit in a warm place for a hr or 2

stator or voltage regulator. are you riding with a space heater plugged in maybe?