I'm a pretty die hard snowmobiler and sold my bikes about 7-8 years ago. I haven't stayed too up to date on the new technology so I feel like a rookie reincarnated with my new/used bike purchase. I've ALWAYS done all my own wrenching, tuning, and maintenance on my mod sleds so feel like I have the mechanical abilities to handle a bike.

I bought a cheap 03 YZ250 last year and upgraded to a YZ450f this year. I'm mechanically aware that filters, bushings, chain, sprockets, bearing play, and misc. fasteners need checked regularly but what else do I need to keep an eye on?

How often should the oil be changed? I ride mainly enduro-style, technical trails, water etc. and then the occasional trip to the dunes.

Also I noticed that the bike had a fork seal that was seeping a small amount of oil. Local shop wants $110 per seal to replace. Seems this is a common occurrence that I should know how to maintain. Do they have a dust seal and an inner seal? Are they Showa forks?

Thanks in advance for the advice.

Yamaha uses KYB suspension.

Your best answer to all your questions is to head to the dealer and purchase a factory repair manual. You will find all the maintenance schedules, how tos and tools you need

make sure you get your valves re-done every once in awhile and make sure you get your jetting done if you go to the dunes cause some people don't and it will screw up your valves .... and if they are showa it will say it somewhere on them!! 110$ per seal is cheap its 80$ an hour for labor in most places but if you get your book from the dealer and are a decent and patient mechanic you can do it yourself...