2009 YZ450F 150 Hours: What Maintenance To Do?

Hello all, it's been a long while since I've posted asking stupid questions about bike setup and maintenance. But it's that time again.

I purchased a 2009 YZ450F new a few months before the all-new 2010's came out, and got the bike for a sweet price! I consider myself very, VERY lucky that I ended up with a Yamaha, as the bike has been nothing but pure awesome since I got it. Is it the best handling, most powerful bike around? For me...YES, because it's the only bike I own!

At 150 hours, the bike is still pretty much perfect. Of course, I have many, many aftermarket goodies piled on. At 6'4", 240lbs, you're not riding a stock bike. Lowered pegs, tall seat, Rox bar mounts, tall bars, Hammerhead brake and shift levers, springs/re-valved suspension, etc., all meant to open up the cockpit and let me ride with something approaching a normal riding style (I ride MX only, by the way).

I've religiously maintained her since new. Engine oil, air filter, suspension servicing, bearings, linkage, cables, coolant, valve clearance...all addressed as much or more than outlined in any service manual.

But...that's where my maintenance has ended...the superficial stuff. I know I'm long overdue for motor work, and here we go...

Can you give me a list of any/all maintenance I should do to keep this bike running in top form for another 100 hours?

Much appreciated!


Something I did at 100 hrs was Valve seals and Springs, Piston and rings (although they still have service life on them) and replaced clutch plates and clutch basket. The basket was starting to show grooving so I replaced it with a GYTR Basket. The plates were on the short end of acceptable limits. The piston and rings still were within limits but since I had the parts, I decided to replace them for piece of mind.

With that said.... Have you done a leakdown test? When was the last time you measured your valves? What is your current clutch life?

I'm not a fan of splitting cases unless I have to so I don't replace internal engine bearings unless I'm getting signs of failure.

Tear it down and have a look, everything could very well be within spec but I would replace the cam chain.

Forgot about the Cam Chain, good catch. Cheap Insurance.

Gentlemen, thank you for the replies. Unfortunately, I'm a novice when it comes to motor work, but I'm going to take all the time I need to learn. Have to start somewhere!

One thing I failed to mention was that I dropped in a Hinson clutch basket about 30 hours ago, and I'm on my 3rd clutch pack. The OEM basket was notched all to hell.

Okay, so even though I'm going to replace piston and rings, I'm still going to perform a leakdown test so I can gain that knowledge (and add that tool to my kit).

I'll do the leakdown test, then tear down the top end (according to the service manual), checking tolerances along the way. Once it's torn down and everything checked, I'll make the decision what to replace. Regardless, I'll be doing piston/rings/cam chain. Then, of course, anything that I find along the way.

Are there any items that I should replace because I'm going to be in there anyway? Valve springs, for instance?

Many thanks, guys.

Like I said, I replaced Valve springs and seals while I had the head off. I have the spring compressor, although there are other ways to do springs without it. I just figured, while I had the head off, I would use the opportunity to replace the springs and seals since they didn't cost a whole lot more. After working on a number of bikes, I've really started to value the maintenance required on the modern 4-stroke.

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