Motorcycle Repair: 2 stroke radiator, head gasket leak, losing coolant

Question
i'm losing coolant out the overflow tube but not until bout 15 mins. into a ride.coolant thats coming out of o.flow tube looks like foam ,is this due to aereation(air lock)or possibly from head gasket leak(combustion into the cooling system)?

Answer
Hi JR.
 Hard to say without actually seeing the coolant.  If it looks brownish in color coming out of the overflow, then you may want to drain the oil and see what it looks like.  If there is oil in the coolant and/or coolant in the oil, then you could have any of a number of problems ranging from a simple oil seal replacement at the water pump, to a crack in the head.

There could also be a problem with the radiator cap.  It could be a failure of the pressure seal in the radiator cap or the cap not being on tightly enough.

Start with those and see what you find.
Good luck and ride safe.
FALCON