I'm trying to bleed the front brake on my 2009 YZ450F using the back bleed method with a syringe, but I can't force any fluid from the bleed screw up to the master cylinder. I could get fluid to return to the MC compressing the pistons, but only by using a C-clamp with a lot of pressure. I'm guessing the MC valve is not allowing fluid to return to the reservoir...can anyone confirm that? Any other suggestions? This brake has always been really tough to bleed. Thanks.