2006 WR450 Rod Knock?

I have a stock, relatively low hour (maybe 200 hrs) 2006 WR450 and I am hearing some knocking sounds during low RPM high load conditions.  It sounds like a rod knock but I would think a bad rod bearing/wrist pin would knock at all load conditions (i.e. idle, low RPM/high load, high RPM/low load, etc.).  It doesn't sound like detonation (I think)......i run 91 octane at about 5000 ft elevation, so I think the chance of detonation is low.  There has never been any metal signs in the oil (changed regularly) but the knocking seams to be getting slowly worse over time.  Also, it has an aluminum GYTR engine skid plate, which I understand makes these motors seem noisier, but I am getting concerned as I don't want to launch a rod through the side of the motor.


I have 2 intake valves that need to be re-shimmed, so when doing so, I will just go ahead and pull the head/cylinder off to check for any play.  


Is there any other easier way to check the rod bearings without taking off the head and cylinder?


Any comments would be greatly appreciated!

There is no way to check without the removal of the top end, but, you're reasonably correct that a loose rod should be prone to rattling under other circumstances.  In fact, it should be more prone to it at higher speeds and lighter loads.  Are you certain that it's an internal noise?  At low speeds under a load, the bike is prone to "chain slap", a result of the widely spaced power strokes whipping the chain into slapping the swing arm; loud and annoying, but otherwise harmless.

it could be your timing chain loose as well you should tare down and find out what it is>

Grey racer said chain slap and sometimes they are noisey. Especially with a aluminum skid plate. However if you ever ran it low or out of oil it could be fried.

Thanks for the feedback......after posting this I did find a thread on the chain slap problem.  I'm going to try doing the silicone under the slider thing before tearing down the top end to see if it helps.


The timing chain tensioner seems to be working fine and the motor has at most 75 hours on it and have always keep up with the oil level and changes, so hopefully only the drive chain slap.


I will update after this weekend.........supposed to be 80 degrees here in Nevada this weekend so we'll see what happens!

A slightly loose skid plate can cause noises similar to what you are describing.

I had the same problem, turned out to be chain slap


Take you bike now and drive it up and down the street

you should be able to replicate that noise.

Make sure you can reliably make that noise happen


Then tighten up the chain, maybe even a bit more than you ordinarily would

Drive it up and down the street and see if it goes away


90% chance thats your problem

It sound just like a rod rapping and scared the Shi# out of me too

I thought I had a blown motor!

Update......I tried doing the silicone sealant under the swing arm chain slider.  Problem Solved!  I also tried adjusting the chain to the tight side of the tolerance as well. 


Went for a ride this weekend and the knocking sound is totally gone.  Glad it wasn't a rod bearing!

  I also tried adjusting the chain to the tight side of the tolerance as well. 




DO NOT run the chain tighter than the specified minimum for any reason.  If you do, the chain will be drawn taut as the swing arm passes through the center point of its travel, and when that happens, something has to flex, bend or break to allow it.  Usually, the chain will let go, but that's not always a minor failure, as it will often take out the crankcase in the process.  The second most common failure that results is to either tear the sprocket flange off the hub, or break out the drive side bearing pocket in it.


"Tight side of tolerance" is OK, just not any tighter.

Thanks Grayracer.....great point!  I have always been cognizant of running too tight on all my bikes in the past (ok in the way past!), and so perhaps a time or 2 I've run them slightly too loose....which probably isn't good either.  Will keep a close eye on it in the future for sure.


I appreciate all the advice......I'm finally starting to get some confidence in working on these new 4 strokes and the advice on TT has been great.......

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