Hey guys, new to the forum. I'm looking to rebuild my top end as suggested by a Yamaha mechanic. I bought my bike brand new in 05 and have been having alot of trouble getting her started while out on the trail. Ive adjusted the valves already and it didn't fix the problem. I believe Yamaha suggests the top end be rebuilt every ten hours? So I'm looking for some additional advice, rebuild or not? I do all trail/desert riding with an occasional trip to the sand dunes here in So. Cal. My bike is an 05 YZ450.