I put a new top end in my 2001 YZ426, including new (stock) piston, rings, etc. I also had new valves, springs, guides and such put in the head. I've timed the engine according to the manual. "E" is at 9:00 on exhaust cam and "I" is at 3:00 on intake came. The cam lobes are facing away from each other and the timing mark is lined up on the flywheel. The cam caps have been torqued to the proper spec and everything appears to be ok. When I attempt to kick the bike, I get about half a stroke and then the kickstarter will not kick through. The timing mark on the flywheel is very close to being lined up and the piston appears to be at TDC. However, the exhaust cam lobes are pushing down on the lifters and wont rotate through. What am I doing wrong in order to get this condition. Like I said, the timing initially appears to be good. Any advice would be greatly appreciated. Thanks.