Zongshen RX3 (overheating) venting the cooling system
 

Recently, it got hot outside, and unfortunately, the temperature gauge started showing four bars, which hadn't happened before. So, I decided to tackle this issue. I studied the cooling system and found out that there is no option for the left radiator to self-bleed. It's an impractical design, and only the right radiator can be bled. Therefore, I removed the left cover and loosened the clamp of the upper hose. It turned out that there was a lot of air trapped, so I released it by inserting a plastic spoon between the radiator hose and the coupling. Once the air was released, I started the motorcycle to let it heat up. When it warmed up and the fans turned on, I repeated the procedure three times. This was necessary because when the system heats up, the air expands, and it might not all escape during the first bleeding. After bleeding, I hopped on the motorcycle and went for a ride, including some challenging terrain. I also encountered some traffic jams. After waiting in traffic, the temperature gauge showed four bars, but after moving and riding for a while, it went back to three bars. I believe that was the reason why the old coolant was boiling over, rather than a faulty thermostat. When the air expanded, it exited through the expansion tank, causing bubbling. Now everything is fine. I'm attaching some photos. I hope this helps someone because I couldn't find a method anywhere to bleed this system, so I came up with my own. Therefore, when the coolant is boiling and the temperature gauge is acting up, first thoroughly bleed the system before considering replacing the thermostat or other components.

Thanks for the diagram Lukas.
I rarely have 3 bars, usually 1 or 2, and I have wondered about air in my system and/or the overcooling issue described earlier in the forum by Katflap and Pyoungblood.


Can you tell me if there was a nocticeable difference adding the oversized from brake rotor kit on your RX3? Would you do it again?
Thanks,
BillR

Of course, the diameter changes the torque of the disc and with it the moment of force of the brake caliper, but to make these brakes really go well you need to replace the pads with sport pads and grease the pistons otherwise the pads will squeal unfortunately my motorcycle, because I have not ridden 2 months lost the rear brake and the oil became coffee-colored I think the coolant pump seal let go or the head gasket I need to look into, but so far somehow I do not have time.

Did you get spare 84mm gasket when you ordered the bore kit?