Manual free need a torque spec on the castle nut, front spindle, just replaced bearings in hub, thanx.

Castle nut is usually backed by a washer that is keyed to the stub axle either by a flat on the threaded part of the axle or by a groove or in rare examples by a splined shoulder.
These are merely precautions because a healthy bearing assembly should roll smoothly without any turning of the inner on the shaft and if this is so there is no or minimal turning force exerted on the washer, nut and cotter...

Assuming it is a typical hub with a pair of taper roller bearings, the most common reason why a turning force is exerted on the outer bearing inner race is over-tightening - there is a general and incorrect belief this type of bearing should be adjusted so there is no detectable free play.
Where the hub also carries a brake rotor, it will become warm or even hot in use and expand and that expansion will be at a greater rate than the axle and so will have the effect of tightening the bearing, often with the predictable result of bearing damage, the bearing turning on the shaft and perhaps even losing the nut, etc.

The correct method of adjustment is not to feel the free play by rocking the wheel - some of what is felt is the clearance between the bearing and shaft. The correct method is by measuring the hub end-float with a dial gauge, though tightening the nut finger tight and unscrewing it by one castellation before fitting the cotter serves most applications and is far less than that recommended by the bearing manufacturer. You will of course need a new washer.

After losing the wheel twice I would suspect both the bearings and the stub axle will have sustained some damage...

search engine are more efficient. If this isn't to your liking
https://taotao.zendesk.com/hc/en-us/articles/204167645-General-Torque-Spec-Settings-
try searching "clutch nut torque spec"

1. First jack up vehicle.
2. remove tire/rim
3. remove cotter pin and castle nut from the end of the axle.
4. disassemble spindle from upper/lower ball joints'
5. separate spindle from axle by pulling spindle away from the vehicle.
6. with two hands grasp axle and pull firmly to remove axle assembly from differential.
7. remove torn cv boot, clean all old grease from cv joint.
8. apply new grease and install new boot.
9. secure clips on cv boot.
10. Reassembly is reverse of disassembly.
11. Consider purchasing the service manual for your make /model of atv from amazon. This manual will have step by step instructions and pictures for any repair or maintenance that you will need to perform.

Not having a manual or knowing the bolt thread size ..I would be guessing...can't guess!!!
Being a diesel the torque will have be very close to factory spec's.. no more that 10% above factory spec...I do not have a manual.. google the specs..sorry

Going by this it would be 110 foot lbs...this was VERY hard to find...and I found it here...http://www.maultechatv.com/techguides/Service%20Manuals/YAMAHA/ATV-SxS%20Service%20Data%201995-2009.pdf

Hope this helps took me an hour to find this...

google for a gy6 service manual. shouldnt be hard to find.

http://www.imperialsupplies.com/pdf/A_FastenerTorqueCharts.pdf

remove the wheel then undo the big nut in the center then remove the brake caliper then remove the big nut and the hub will come off !

The hub should pull off by hand after the nut is removed however the bearing is pressed in most machine shops will press the old one out and the new one in for little or no charge

pretty simple..take both hubs off each side..remove the two axle lock nuts. axle will only pull out to one side..not sure exactly whicj side. take a hammer and punch to the our race of each bearing. press not pound the new bearing in and use lots of grease.