125-200cc 2014 WR300 started smoking coolant

I'm guessing it's the Cyl head O-rings. Are these a maintenance item? If not what should I do to stop this from happening again?

What do you mean smoking coolant? Where you in a tight single track and the bike started to boil over or riding flowing trail and started to boil over? Could smell it from the exhaust?

good call omg....where exactly is this thing smoking from? and no, the cylinder head oring is not a wear item, its just something just that is generally changed every time the head is removed. not something removed often...

Sorry I was almost fallong asleep when I posted this. It was coming out of the exhaust. I was in some tight stuff earlier but this has happened around 20 mins later after some pretty open trails.

Yep, inspect the o-ring and check the coolant level as it should be very low. O-rings are pretty cheap so replace it and worst case scenario is the water pump seal or possibly a base gasket...you'll have inspect one by one carefully but my money's on the head o-rings (do 125's run 2x oring seals?).

There's only a few places it could leak coolant into the exhaust. Head o-rings, base gasket, cracked cylinder or head. If the water pump seal leaks, it leaks into the transmission oil. Also, if you have the factory coolant in there, flush that crap out.