NEED HELP coolant and oil mixing

I have a crf250r. The coolant is mixing with the oil and making thick white smoke when its running. I already changed the head gasket, that didnt work. It could be a warped cylinder but theres good compression. Is it a water pump seal? NEED YOUR ADVICE BEFORE I BUY ALL THESE PARTS!!

If anyone can help me that would be GREAT! Im getting sick of taking apart this bike.
like Mihylo33 said water pump seal, my KX250 did that to me the coolant was mixing with the tranny oil. Made my clutch so sticky it was horrible! What was even worse was I had to split my case to fix it :banghead::banghead::banghead:
Jcop550 you see to much withe smoke, these smoke smell like oil?

It´s possible you have seat valves with clearance, and by this your bike can have overpressure in coolant circuirt and this is way some gasket is not doing his work mixing oil and water..

I don´t know if is understandable what I say....