MZ/MuZ Riders

good day all;

Got an overheat problem, new to the bike so not sure what it is. Friend gave me the bike its a 2002 125 sm. Had a mechanic clean the carb and it runs nice, however the overheat turns on when I get underway but does not seem to on idle. I checked the oil, level is good and oil is clean and foam free with no sign of any anti-freeze. I opened the radiator cap, topped it off and can see it swirling around inside but don't know at what intensity it should be at. Guessing it can potentially be the thermostat but not sure.

Any suggestions would.

What is an overheat, is it American for radiator fan ?

What I mean is that the overheat alarm light turns on.

Open the rad cap with the bike off then crank it up, you should se the water level drop a bit. If not, water pump could be bad. Im not sure if these bikes have thermostats, will get back to you on that. If its not leaking, consuming water at all, flush the system really well and pull the coolant temp sensor, if its all cruddy it could give a false reading. Lastly, when the light comes on, put your hand near the radiator, should be warm enough to feel but not super hot. Good luck bud. Brian

Thats a positve on a thermostat. Check it to make sure its not in upside down and is opening as its supposed to. Boiling water trick to make sure it opens. Cheers. Brian

boil in pan of water
and speed up the idle a bit these idle 1800-1900 udm

you may not be moving enough water

my rt125 only comes on when i stop and talk to a neighbor on a very hot day

the sm sx bikes have 2 cooling cores and may need more water pump speed to get proper coolant flow

and is the fan coming on ..my rt125 fan very seldom comes on