Need Help mountain max blowing coolant nipple out of the head

[live2rideyamaha]

my buddy and i just finished up installing a used motor in his 03 MM 700 we took it out yesterday and about 2 miles into it the plug in the top of the head that runs coolant to the carbs popped out of the head. so we went to the yamaha shop and bought a new plug and pushed it in, then it ran great for about an hour and a half, then it blew out again. are these plugs suppose to be sealed in or whats the deal. Is the motor suppose to have a thermostat? we are suppose to be leaving on a trip in three days and i am trying hard to get it fixed. any help would be great
thanks

 

[maxdlx]

clen the plug and head both. put red loctite on plug and push it in. let it sit for at least 12 hour and good to go

 

[live2rideyamaha]

mm

ok I will try that. does this sled require a thermostat.

 

[Mountain Boy]

No thermostat on this sled.

 

[Givemeaboost]

Make sure you get the air bled out of the system. There should be a bleeder in the crossover under the tail end. Raise it up a bit and open the bleeder till the air quits bubbling out.

 

[live2rideyamaha]

mm

ok thanks for all the help guys, should have it all fixed up tomm

 

[DOO800RIDER]

These can be a pain to get all the air out. Whenever I have mine apart i always carry a gallon of 50/50 water/antifreze for a couple of rides. Check coolant level regularly and top off as needed! Ther is also a bleeder in the water outlet on the head, The part that look like a t-stat housing.