06 450 noisy so I tore it down.. now what

[blue9red9]

I bought a used 06 450F and after comparing it to my brothers bike it was much noisier with the low speed clinking noise. So this afternoon, I removed the head and cylinder thinking it may be the big end of the rod. It's all tight... no apparent crank problems. The webbing at the big end of the rod is discolored but nothing is loose. Is the discoloration a problem? I know the bike was raced hard in the past. How do I know if it needs a piston? It ran fine and the cylinder and piston look fine. Should I put a piston in it if it has been raced and has over 50 hours on it? What are the signs? Is it the same as a two stroke where it would show physical wear cause it really shows nothing.

[Foxman06]

yamahas are known for being noisy, but as you said it has been raced so i personally would change out the piston. Check the valves while your at it too.

[blue9red9]

When you look at the piston on one of these 4 strokes, how do you know it needs to be replaced? Is it obvious or are we talking about micrometer measurements and out of round cylinder specs like on a car?

[grayracer513]

The bluing of the crank at the crankpin is done at the factory and it's normal.

The only way to determine if the piston is too loose is to measure the clearance.

[blue9red9]

I had a feeling the blue crank was done at the factory to put it together. Every one I have ever seen has been like that, bad or good. So I guess I'll put it back together after I do some measurements. I can't imagine it's going to be bad the way it looks. My mind will rest easy now when I hit the track next time. Yamaha is truly the bike of my choice after how good this engine looks and what it's been through. Valves look good as well, nice seats and guides.

[Fastdaddy]

Why you are in there I would at least put rings in and hone it.

[blue9red9]

I was thinking rings and a piston but can the cylinder be honed. Doesn't it have some sort of coating on it? It's shined up but not scuffed anywhere.

[Markopolo400]

Throw in a new piston, rings, valve springs, valve seals, and keepers while you are in there.

It's cheap insurance, and you'll get to see the valve faces. If they are L shaped, replace them as well.

[Butta]

Throw in a new piston, rings, valve springs, valve seals, and keepers while you are in there.

It's cheap insurance, and you'll get to see the valve faces. If they are L shaped, replace them as well.

Don't forget the cam chain....more really really cheap insurance.

[grayracer513]

I was thinking rings and a piston but can the cylinder be honed. Doesn't it have some sort of coating on it? It's shined up but not scuffed anywhere.

When replacing the rings, the cylinder should be honed to insure a quick and effective seal. Use a "spring ball" or "bottle brush" hone, and hone only as much as required to break the glaze on the entire surface.

The cylinder is plated with a nickel silicium carbide compound called Nikasil, which is extremely hard. You won't remove a significant amount of it by honing lightly as described.

[Markopolo400]

Don't forget the cam chain....more really really cheap insurance.

Haha, yup, forgot the cam chain. Replace that too.

[blue9red9]

I found a couple of the valves had closed to their min. clearance so those will be shimed. Other than that, piston + rings. My buddy had a 426 that got wicked noisy. His clutch basket nut had come loose within the locking tabs. Something was not quite seated when it was put together so it never got all the way tight I suppose? It quieted back down. Strange. I'm just going to ride this 06 after the shim kit comes in and keep my ears open but not worry anymore.