2006 Noisy

I've searched this before, but would just like some confirmation. I have a 2006 YZ450F. Last year, the top end started getting noisy. Valves were OK, but re-shimmed since then. Decided it was the cam chain worn, so got a replacement from Rocky Mountain, since I read that the OEM chains could stretch. I am second guessing myself now, but I thought at the time that the noise was gone, and it sounded normal at the start of a 80 mile ride, first time out. By the end of the ride, it was back again. This was in April, and since it has gotten progressively louder.

I have a 2001 426F that I recently re-built, and it has no top end noise. The 2006 is downright obnoxious. I pulled the flywheel off and the valve cover, and cannot see anything amiss. Probably have 500 miles on this new cam chain. Is it possible that it just stretched in that first 80 miles?

I did not replace either guide, as they looked OK, nor the tensioner, as it appeared to be OK. Should I just try a new cam chain, or should I do the whole bunch; both guides, tensioner, and chain?

I supposed it's possible that the chain was just an inferior product, and stretched, but that seems odd. By the way, the cams rotate smoothly; no binding. The guides also look OK, but perhaps a little wear is enough?

Suggestions welcome.

Come on guy's, a little help here!

There's probably something wrong with the 426 that doesn't make noise.

YZ450's are a noisy engine. The '06 is noisier, not because of the engine, so much, but because of the fact that the aluminum frame tends to attenuate noise better than steel.

Now the key question: Do you have an aftermarket skid plate?


When I say the 426 is not noisy, I mean it sounds reasonable.

As to your question on the skid plate, yes, I put one on at the same time as I replaced the last cam chain. If that turns out to be the cause, I'm going to feel real stupid. I will pull it off and see if there is a difference.

Tied up for a few day's, but I'll post after I check it out.


You'd be surprised how much noise they can make. I've even taken one off my own bike, put it back on just a little differently, and had it make a whole bunch more noise. Line the frame rails with rubber from an old bicycle tube.


Pretty late in replying on this; you were right, it was the skid plate. Added the rubber strips, and found the top half of the plate, not being secured in any way, was acting like a speaker, so ran a zip tie to the frame. Just tapping it with a knuckle made noise prior to the zip tie. Still emits some noise, but probably 25% now of what it was. The explanation you had of the aluminium frame makes sense too, so as not to compare it with a steel frame.



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