Hello all. New to this forum. I just purchased a Blue 2012 300 4X2 last week. It only had 5 hours ran so it had set in the garage a lot unused. This is my first ATV so I am a complete noob though I have worked on other toys.

On to my problem. When I purchased it the rear brake did not work, I just assumed it needed adjustment. This model has a single disc and caliper just left of center on the rear axle. I bled the system and initially all was working as it should. After about an hour the rear was spongy again and not working. Figured out pretty quickly that brake fluid is leaking from around the piston on the caliper itself. My guess is blown seal on the caliper piston, possibly dried out due to lack of use?

I have not broken down the caliper yet to remove the piston but I cannot seem to find any o-ring information on the rear unit. I can only find a reference to the complete caliper to purchase for $215-$260. Other models and years have broken down schematics for all parts including the o-rings but for some reason nothing on this year. I hate to spend $200+ to replace o-rings that are less than $10 for other models (and might be the same part). I found part # 3GD-W0047-00-00 that points to several 2012 and 2013 model o-ring sets but nothing for the 300 model. Any thoughts?

Hello all. New to this forum. I just purchased a Blue 2012 300 4X2 last week. It only had 5 hours ran so it had set in the garage a lot unused. This is my first ATV so I am a complete noob though I have worked on other toys.

On to my problem. When I purchased it the rear brake did not work, I just assumed it needed adjustment. This model has a single disc and caliper just left of center on the rear axle. I bled the system and initially all was working as it should. After about an hour the rear was spongy again and not working. Figured out pretty quickly that brake fluid is leaking from around the piston on the caliper itself. My guess is blown seal on the caliper piston, possibly dried out due to lack of use?

I have not broken down the caliper yet to remove the piston but I cannot seem to find any o-ring information on the rear unit. I can only find a reference to the complete caliper to purchase for $215-$260. Other models and years have broken down schematics for all parts including the o-rings but for some reason nothing on this year. I hate to spend $200+ to replace o-rings that are less than $10 for other models (and might be the same part). I found part # 3GD-W0047-00-00 that points to several 2012 and 2013 model o-ring sets but nothing for the 300 model. Any thoughts?