Sometimes a little heat is needed. On my little brothers KX500, we found the bolt had been loctighted in with bearing strength loctight (you can tell by the colour- dad uses it a bit)
Application of gas torch, impact driver and hammer required
On the bright side, you didn't neet anything to stop it turning. The compression was sooo huge. (My older brother can't start it... too lightweight to push the kickstarter down )
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The Chopster