2001 500 HO is stuck in High Forward gear

The front break usually over rides the starter sensors. Squeeze it and try starting . You can try rocking the machine forward and backward while trying to get it into neutral.

Need more info.. removing brake lines is pretty straight forward.. why are you needing/wanting to do this...

More details please...

Sounds like a bad bearing or shaft in transmission.
Check the attached links,Manuals and guides, Good luck with your Bike
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ATV TROUBLESHOOTING AND MAINTENANCE
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Don, if it is in high 4x4 probable transfer case bearing bad.
Check the attached links,Manuals and guides, Good luck with your Bike
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."

ATV TROUBLESHOOTING AND MAINTENANCE
Service Manuals for Download in PDF
ATV Service and Repair Manuals

My 2005 Polaris ATP 500 requires I depress the right foot brake while shifting into reverse or down into low range. Perhaps some adjustment on the foot brake to make this work. Also check linkage to make sure it is not binding. Others say if the idle speed is too high, you may not be able to shift. Try shifting with the engine off to see if it goes into the gears, using the foot brake. If yes, try again while at low idle speed.

Try taking a look at the starter and flywheel while attempting to start the engine. Does the small gear at the end of the starter move forward and engage the flywheel when you try to start the engine? Could it be stuck? The small gear must move forward to engage the flywheel. Keep your fingers away from the moving parts.

same happen to mine

sounds like the connecting rod on the crankshaft.
i would inspect the primary clutch first before an engine teardown. Sometimes the engine shifts on the engine mounts and the clutch hits the cover, also check to make sure belt is not slapping around in cover.

Clutch not disengageing or engine idle speed to high clutch may not be disengageing from engine speed to high

Is this an electric shift?? SORRY.. take it to a qualified professional!!