by JimDirt » Sat Mar 26, 2016 9:28 am
When you had the head off , how did the piston look ?? , was it completely clean of carbon (or mostly clean , not spotless) , or was it "normal" and sooted with a carbon buildup ??
If the piston was really clean , it would mean the coolant was leaking into the combustion chamber , if its was covered in soot/carbon , then there is no leak within the cylinder
Also when you ride what type of riding is it ?? , is it REAL SLOW tight single track ?? , or are you able to get speed up and ride thru the gears ?? , or somewhere in between ?? , as you will get some coolant loss due to steam , from going real slow all the time , if the bike heats up enough during a ride to steam over from lack of air going thru the radiators , you will get "some" coolant loss , as the overflow bottle is not a sealed unit , it still has a overflow , and coolant can and will escape during extended periods of low air flow , since air flow is the ONLY cooling the coolant gets unless (like me) you have a cooling fan on one of your radiators
In other words , do not expect it not to lose "some" coolant on a ride , especially if its a slow hard , or hot day ride , but if its a major loss and the riding was easy , then there would have to be another cause
Have you inspected the overflow tank for leaks ?? , maybe a cracked seam ?? , i run a 250X bottle on my 450R , and i still get a slight loss of coolant , but not enough to cause overheating even after several rides , and not nearly as much as i would without a overflow tank
A cup of coolant loss per ride seems extreme , if it was a head gasket and its not coming out the exhaust (white sweet smelling smoke) , and your piston does not look exceptionally clean , and not turning your oil milky colored , then it has to be going out the overflow
2020 CRF450R
2006 CRF450X

Weiser , Idaho