SM 125 coolant overflow when running

[roloscotusa]

Hi,

My SM125 blows coolant out of the overflow pipe. This typical starts after about 15 miles of riding. The bike will eventually overheat one the sufficient amount of coolant has been blow out of the overflow pipe. Both radiators are getting hot. The bike is not running crazy hot. The cooling fan does come on when hot. However you have to ride it to get it blow water out of the overflow pipe. Having the bike stay stationary will not cause the symptom.

The following has been checked:

- Replaced radiator cap

- Checked all hoses and clips

- Replaced thermostat

- Pressure check the engine - compression seems to be ok.

- Got the air out of the system including bleeding air from second radiator.

Any suggestions would be greatly appreciated.

[den]

you know for definate your water pump is spinning and pumping with adequate pressure..
have you put thermostat in upside down??..

try it without stat,,wont hurt,,

i suspect either of the above,

i would just connect the cooling system to a garden hose and turn tap on ,, allow constant flow of cold mains water,,start engine and see if it overheats as it did before,

[DAVID THOMPSON]

i must be lucky just short of 21,000 on my rt125 and 13 years and all i do is take the cap off and check the level
every so often
i have added less than a pint of 50/50 mix in that whole time

dave

[roloscotusa]

When say connect the garden hose - Do you mean take the radiator cap off and keep topping it up with water. Thanks for the suggestions

[den]

When say connect the garden hose - Do you mean take the radiator cap off and keep topping it up with water. Thanks for the suggestions

no , i mean actually plumb it into the system where to hose to the waterpump goes into the engine,,and the hose that you have undone just prop upright, ready for the water to flow out,

dont do it if you dont understand,the idea is to use the water pressure of the mains to replicate the flow you would get from the pump,It cant be a closed circuit for this reason so youl have water pissing everywhere but what it will tell you is cold water is cooling the cylinder jacket and the cooling system is not blocked,,

[den]

how have to tested your water pump??

[stephendacosta]

I suspect the water pump. I have the same problem with two of mine. When I get home on June 8th I will be going in to them to see. Eliminating the thermostat had no effect, so it's about the only thing it could be. I even rigged an overflow bottle to see if the radiator might recover the fluid on cool-down(didn't). Might be a weakness in the design, since this is now the third one in a year.--Steve