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valves question

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My 02 CRF 450 has been making a weird noise on the top end and ive been tryint to figure out what it was. Tonight i was checking to see if possibly the rocker assembly bearings were bad. They dont seem to be. I was slowly kicking the bike over and over watching the valves and i noticed something that im not really sure about.

Here's what its doing.

The cam hits the exaust valves they open and close.

The cam hits the intake valves they open and close.

On the way back around to the exaust valves, i noticed that the exaust valves move a little bit as the cam continues towards the exaust valves. They slightly go down and then back up and as the cam continues to go around. The camshaft hits the exaust valve again and they open completely and then the cycle continues.

Is it suppose to be doing this?!

ANY thoughts are highly appreciated!

Keith

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It's the auto decompressor system. It's really neat.

Check it out, there is a spring and a light weight on the camshaft. When your engine is spinning slowly, ie after you kick it (or as in your case move it slowly by hand) the spring holds the weight. There is a goofer that actuates the arm that in turn opens the exhaust valve. That releases compresion on the upstroke. Ever stall your engine and have it start back up again magically? That wouldn't happen on a yamaha. On a yamaha you pull in the manual decompression unit and that opens the exhaust valves.

Anyway the neat thing is that when the engine is turning. The spinning camshaft causes the little weight to open outwards, and the little goofer/notch does not come into contact with that arm actuating the exhaust values.

If you've still got your cover off try this:

Hold out the little weight with the spring that should be on the opposite side to where the chain is. Now turn the engine again. You will see that this time the exhaust valves dont open. You will also find it a sonofabitch to turn the engine any further. That's because you have full compression now. That's how your engine runs when it's at normal operational speed.

After you do that do the following:

1) Check your valves are in spec.

2) Put everything back together.

3) Drive the bike. It's fine. :cry:

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Are you sure it is not the clutch basket cushions (donno if it is the correct word) that are worn? My bud had them gone and the noise seemed to come from the top, but when we drained the oil we got black rubberpieces out. It was a common problem with '02 model. :cry:

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