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czechalien

Valves leaking?

8 posts in this topic

Just opened up my 09 YZ450F to do my first top end and 2 of the intake valves seems to have some oily residue on it, is it oil? do I need to replace valve seals?

Did it damage valve seat at all, if so could it be fixed or do I have to buy new valves?

I noticed it was harder to start, also popping more often and dying when in low rpms.

Mark

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It's normal to see the 2 outer intake valves covered in an oily looking carbon while the center intake looks like brand new. When I do a top end I disassemble the cylinder head to clean and inspect everything and at that point I always replace the valve stem seals. What you are describing sounds like typical Yamaha to me.

The poppong issue could be that the carb needs a good cleaning.

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few pics. on the cylinder u can still see the criss cross pattern. I cant feel any indentations near the top either.

DSC04803-Copy.jpg

DSC04806-Copy.jpg

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how much have you ridden that bike to be doing a topend already? i cant see the pictures on this computer until tomorrow but if in doubt measure.

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Just opened up my 09 YZ450F to do my first top end and 2 of the intake valves seems to have some oily residue on it, is it oil? do I need to replace valve seals?

Did it damage valve seat at all, if so could it be fixed or do I have to buy new valves?

I noticed it was harder to start, also popping more often and dying when in low rpms.

I would replace the valve seals anyways as a piece of mind. They are cheap and easy to install.

Have you adjusted the valves at all? When you remove the valves to replace the seals you will be able to check the valve seats. If the valves are starting to cup then you will have to recut the seats and replace the valves.

This might have been due to the valves being out of spec as well.

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I have 58 hrs on it since I bought it new in March.

Cylinder is in greta shape had someone hone it, so no problem there.

Also valves looks still good and to my surprise still in spec after 58 hrs.

received new crancase1 gasket and cam chain today so that's installed.

Still waiting on the rest.

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I got 246hrs on my 06yz450 before I did a full rebuild on it. I adjusted the valves right after I broke her in and that was it. I took very good care of my bike and rode the heck out of it.

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