its a 2000. twice i have taken it on a 150 mi trip and both times i had to fill up the coolant resivor. the last trip i did twice it went from max to min then i filled it then at the end of the day it went to min again. I changed the oil and it looked alittle brown but not bad. but it seemed like there wasnt all that much oil in the case but there was plenty in the oil tank. and my spark pulgs are oil fouled. my ds runs good and idles fine. I put a tm45 on it used said it was off a ds650 could the oil foul just be a jetting thing? but it runs good. so my question it could it be my coolant seal or a bad head gasket? or do the ds650 evaporate coolant? thanks for your help.

 

is it going to min after the bike cools down? I ask to rule out the possibility of it being over filled. if it is on "min" when the motor is cold, it will expand to "max" after riding. if it is filled to "max" when cold, it will overspill upon thermal expansion, and then be back to "min" after cooling down, as it should be.

if it is losing coolant other than described above, the first most likely cause would be a leaking pump seal. inspest the wheephole under the water pump cover, if antifreeze is dripping from it then there is your problem. replace BOTH seals and also the shaft - failure to replace a scored shaft will immediately destroy new seals.

if wheephole becomes plugged with dirt, leaking water will then be forced through the second seal and into the case, but this does not sound like you case, as you seaid your oil has no water in it.

if the seals are fine, but coolant is being constantly forced out the expansion tank overflow, then the likely cause is head gasket, but blown head gaskets on stock motors is not at all common so rule the other stuff out first befreo ultimately having leakdown test done to the motor to determine if it is indeed the head gasket.

when filling the cooling system, leave radiator cap off, start motor and let idle to point of warming up and thermostat opening and coolant begin to circulate. you will see the level drop, and bubbles come up. continue to top it off until no more bubbles and flow through radiator can be seen, then cap it and fill expansion tank to slightly above min mark.


as for plugs, tell us your current jetting. your pilot otta be around 30, needle otta be a # 97 on 2nd groove from top, pumper jet otta be a # 50, and your main depends on airbox arrangment but certainly would not not need to be bigger than a 165-170ish even if total airbox ellimination at sea level.

 

Well its not the first thing you said about the mion and max.
And i dont see anything leaking out of the wheephole.
And i dont know what jets are in the carb its a tm45 i bought of e bay and have never opened it up.

 

so where is the missing coolant going? its either pooring onto the ground or going into the crankcase. its gonna get to the ground through a leaking hose, leaking radiator cap, coming out the wheephole, or coming out the expansion tank overflow. its gonna go into the crankcase through pump seals. all of which should be identifiable visually after running the bike to operating temp.
if it is indeed coming out the expansion tank overflow, the cause is head gasket - combustion pressure getting into coolant system - assuming of course the radiator has been properly filled as described above. air in the coolant system will cause a steam temperature highly than boiling point and purge your expansion tank without ever drawing any coolant from it to fill itself. coolant is only drawn from the tank and into the system when the coolant in the system retracts after the motor cools down, it is not meant to or able to top off a low system, its just a tank meant to catch the expanded coolant after warmup, and then allow it to syphon back into the system as it cools down. if there is air in the coolant system it will never work right, and you will always lose what you put in the tank.


take the bowl off your carb and see what jetting it has in it, and also what is your airbox arrangement - running with factory lid on it, no lid, box removed, or carb mount filter?

 

Just letting everyone know it was not the waterpump seal or the headgasket. i had air in the coolant tank so like hightower said i lose what i put in the tank. and as for the plug fouling it was the carb running rich. i put the stocker back on for now. the main jet was a 142 and i live in minnesota right one?? but thanks for the help everything is running great now!