thought I had a rod knock, I was wrong. What could it be?

'06 YZ450F. So I was halfway across the country at a huge supermoto event when I was doing a double, landed, heard the motor start knocking. got advice from a few others before I axed my weekend, the consensus was the sound was a rod knock. Thank god I had my 150 with me to stay the weekend and play. 

 

So I just put the motor on the bench and tore the top end down figuring I would find play in the rod or crank bearings, feel it by hand. 

 

But nothing, everything feels tight! tight tight tight.

 

The full picture: burns about 6oz of oil each race. cam chain is also tight. checked the valve clearances before I removed the cams. They were all over the place. Intake specs .10-.15 mine were (3 valves left to right) .152 .102 .076 Exhaust specs .20 - .25 Mine were .432! and .178. It has the HC graves piston which only has one compression ring, stock bore. Also graves exhaust that always has play in the header but no way could that have been the sound. 

 

The sound was a knock, when up and down with the revs, sounded like a single rotational knock, like a rod or crank, not like a top end problem.

 

I really don't want to split the cases and spend money if I don't need to, so let the ideas flow, please. Thanks

'06 YZ450F. So I was halfway across the country at a huge supermoto event when I was doing a double, landed, heard the motor start knocking. got advice from a few others before I axed my weekend, the consensus was the sound was a rod knock. Thank god I had my 150 with me to stay the weekend and play.

So I just put the motor on the bench and tore the top end down figuring I would find play in the rod or crank bearings, feel it by hand.

But nothing, everything feels tight! tight tight tight.

The full picture: burns about 6oz of oil each race. cam chain is also tight. checked the valve clearances before I removed the cams. They were all over the place. Intake specs .10-.15 mine were (3 valves left to right) .152 .102 .076 Exhaust specs .20 - .25 Mine were .432! and .178. It has the HC graves piston which only has one compression ring, stock bore. Also graves exhaust that always has play in the header but no way could that have been the sound.

The sound was a knock, when up and down with the revs, sounded like a single rotational knock, like a rod or crank, not like a top end problem.

I really don't want to split the cases and spend money if I don't need to, so let the ideas flow, please. Thanks

how tight ? It should be tight but should have side to sude play a little. If not it's also a bad crank.

that exhaust valve spec id bound to make some noise, Make sure the cam and bucket are not damged

Any signs of metal at oil changes , drain bolt magnet clean , oil filter clean ? .

found the cause, but not the problem. You'll see the clutch basket teeth tore up from the foreign object on the bench, but now I have to split the cases to find what that object is, It's definitely a piece of the case, just don't know where or how much other crap is in/near the tranny. The oil had no shavings in it and the filter is ok. No metal on the flywheel magnet either but the case wouldn't attract anyway. 

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The picture is a bit blurry, but the object looks like a chunk off of one of the locking lugs on the gears in the transmission.

The picture is a bit blurry, but the object looks like a chunk off of one of the locking lugs on the gears in the transmission.

GR, is that part of the case or a smaller replaceable part? I'll have the cases split late tonight, of course the 27mm socket wasn't in my set.

Not sure, but it looks like part of one of the gears.

 

You don't have a 1 1/16" socket, either, huh?

lol I took it as a blessing, if I had the 27 I would have been late for work. this world works in funny ways. 

oh, not a gear part, I'm not excited about finding where it came from cause i have a hunch I might need case half - are these halves matched? HOPEFULLY it's a part that's not needed - DOUBT that

Why would you need a crankcase if there is a piece broken off of a gear? 

 

The part is steel, isn't it?  (try a magnet)

not steel, that's what I'm sayin. It was clearly part of the case when I had it in my hand, and put it next to the flywheel and didn't attract like the balls from the slipper did. I was hoping the lugs were part of the case. OH now I know what locking lugs youre talking about, the 4 or so teeth things on the face of the gears.

If it's aluminum, it should have come from the right side where all the business is,  look there. 

Today, We solute You Mr. Grayracer. For as even with a blurry picture, you can tell a broken loose locking lug, rounded on the edges from getting catapulted throughout the case and final drive gears. Well done Sir, not so much for my pocket. 

In the pics you'll see the broken lulg sitting in its original position, then the inside of the case, and then you can see how it Almost came through the case like a bullet. So I guess JB weld is in order, maybe on the inside. Can you sand that stuff after it dries?

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Yeah, you can fix that with JB, no problem.  Use the regular stuff, not the "quick" version.  I fixed a damaged flywheel cover that way in the desert one New Year's and rode it like that for a couple years after til I found a nice used one.

 

Sand the surfaces clean with coarse paper, like 80 grit or so. (I used a knife blade in my emergency case fix) Really scuff it up to give the JB some "tooth" to hold onto.  get the cracks as clean of oily residue as you possibly can by using carb cleaner followed up with brake cleaner.  Dry it thoroughly and coat both sides.  Sand only the outside for appearance sake.  Clean up the inside only as needed for clearance.

kewl, Thanks. Well, just bought all the parts, basically the same price as if the crank let go, cept this way I get to put the tranny together and hope it works

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