What 2003 YZ450F issues to look out for?

3 replies to this topic
  • sclark309d

Posted May 27, 2012 - 11:31 PM


I've found a pretty nice 2003 YZ450F locally. i have ZERO experience with modern bikes, much less modern 4 strokes.

From what I have read, the general opionion seems to be that Yamaha thumpers are the most reliable compared to the other brands when mainenance was not religiously done.

Do you all concur?

Are there any issues specific to this model I need to look out for?

Thanks in advance


  • BergArabia

Posted May 27, 2012 - 11:46 PM


I had a 2005 YZ450F back in the day, but I bought it new so the maintenance issues were no surprises.

Very reliable for sure. With a bike that old however I would expect to be looking at worn/fatigued rubber parts, things like fork seals, hoses, I would also expect the carb may need a good clean and maybe some attention. You will prolly also have to by new air filters, possibly new bushes and refresh the suspension.

You can check if the valves are in spec, but if it starts easily that would also be a clue.

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  • 2-Stix

Posted May 30, 2012 - 07:50 AM


03 has bottom end issues after about 200 hrs. Keep clean oil. Good friend blew his up and after resurching found the main berrings had issues that year.

  • grayracer513

Posted May 30, 2012 - 09:13 AM


Main bearings weren't the problem, it was the rod bearing. The weak point was the roller cage, which could randomly split and allow the rollers to track out of line, which then led to a seizure of the big end. That could be a minor annoyance (apart from the price of a crank) at low speeds, or quite catastrophic if at high RPM. The problem is that there's almost no way to "see it coming". It doesn't happen to all, or even a very high percentage of them, but it does.

Another thing that will be hard to test for is skipping in 3rd or 4th gears. If the locking lugs on the sides of the gears wear enough, they will start pushing themselves out of engagement under a load, to be forced back in by the deflected shift fork. When this happens, it causes an irregular jerking sensation under a heavy throttle load only in the affected gear that feels like the chain jumping over a tooth, then grabbing again. Some people mistake it for an engine misfire. This is one of the more common issues, but is still something that happens to a minority of YZ450's.

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