Hi I'm New in this forum , and novice in mechanic , i bought crf 2 years ago in thailand .i never had problem before . Afters mods stage 1 with new exhaust and ejk . my engine start to make metallic noise after riding 30mn on trails here in thailand, engine very hot the coolant boiling in the plastic tank. I check the oil was ok Next days i replace stock muffler and injection . Metallic noise still there . Any idea about what happened ? Thanks.