Jonway YY250T out of commission again.

[Shadowfire]

Notes on bleeding the YY250T coolant system:
Several people on forums have advised removing the carburetor heating lines as being useless. These are the lines which carry coolant from right before the thermostat, into the carburetor, then from the carburetor, to the fill cap. Even if heating up the carb is optional, the lines proved a way for air to escape from a high point in the closed system.
Another point to note, is that the filling hose from the filling cap to the radiator is routed such that it goes down from the radiator, before going back up to the filling cap. Unfortunately, after you've introduced air into the system (by taking off a hose, for instance), this design ensures that any air drawn into the radiator cannot escape.
Once the low point in the hose has filled up, there is no where for the air in the radiator to go. When you start the bike, the water pump will draw whatever coolant is in the bottom of the radiator, send it through the engine, and on the return trip, the coolant will simply fall down the side (inside) the radiator and pool at the bottom. Any air drawn in by the pump will rise up to the thermostat and eventually be expelled through the carburetor lines. This will allow a little more coolant to be drawn from the reservoir when the bike cools down, but the hard truth is, only a fraction of the surface area of the radiator (mostly near the bottom) is actually cooling down the bike. I get around this by disconnecting the fill hose at the radiator cap, un-routing it , and holding the entire line above the radiator while filling the tube. Once there is no more gurgling and it doesn't want any more, dump the excess from the tube back into your coolant bottle and reroute the hose to the radiator cap.