I have a 2011 KX 450 and at around 30 hours I had to replace the head gasket because it was leaking and therefore it over pressurized my cooling system and would push the coolant out of the overflow tube. At that point, I would have to refill the radiator after every ride because it would "blow out" so much fluid that the fluid level was below the cores. At the same time, the mechanic (at the Kawasaki dealer) who did the work made sure to re-surface the head. Well, fast forward around 20 hours and the same thing is happening again. I have to refill the radiator every ride because when I come back in from a moto, the coolant level has dropped to around or a little above the cores. I have been using a 1.6 cap that I bought from the dealer, but that doesn't seem to cure my problem. Also, I am just using peak anit-freeze (50/50). I am very critical about checking my coolant level, especially after the replacing the first head gasket. I have other friends with Kawasaki 450's and only one of them has ever replaced a head gasket (and it fixed it). I have searched this forum and I did find that some people did have to replace the head gasket once, but now this is happening for a second time. I am not sure how many of you have mentioned this to Kawasaki, but I sure would like to. Can anyone offer any suggestions about the SOLUTION to this problem. It would be greatly appreciated.