I just changed my spark plug on my 2000 Yamaha WR400F! It's way too hard to change! You got to remove all kinds of crap! I think the Yamaha guys do it on purpose so that you'll have to take it to the Yamaha shop and pay big money to work on it! Since I changed my spark plug I can a big power increase! It's so fast that the tires can't keep up with the engine! Ha! Ha! I just put a new front fender and disc guard on it and it looks awesome! I am going to install a cable lube kit for the cables so I can lube the cables without taking them off!