Take a look at my lapped valve seat please.

This is an exhaust seat lapped twice with course and twice with fine compound. The spots must be carbon (or rust maybe?). How clean do these need to be? I don't have dye but I can get some if its needed to check the seal. Can I lap like mad and not worry about valve clearance or does lapping wear off significant amounts of the seat? Thanks!

The valve seats look like they are pitted. Its time to have them reconditioned. Find someone around you that does motorcycle heads, not some garage that does "valve jobs"

I like the old Kwik-Way equipment that uses shaped stones to redo the valve seats. You want to remove as little possible from the valve seats when you cut the seats. The newest way to cut valve seats is the fancy Serdi equipment. Thats what most big time performance shops now use to do valve jobs. I am old school, I still like the old Kwik-Way stones to cut valve seats. Those old style valve seat cutters that are shown in the Kawasaki shop manual just don't leave a nice smooth seat like the Kwik-Way, or the Serdi equipment do.

yep, valve seats need to be cut........ :pinch: either way, valve shims will need to be adjusted :dry:

Thanks for the input!

This is a kz750 twin with those hard to find 32 mm shims

What if i dont resurface them?

They will leak.
Did you have the valves done?
I cut my own seats and valves. Just got done with a 440 head. It had pitting similar with yours.
I cleaned up the valves, on a lathe since my old Sioux valve grinder has a .0015 runout.
The seats looked good except for some pitting like yours. So instead of using stones I decided
to try just lapping them for a change. It took a little while to get it done. They might be a hair
wide, but they cleaned up just fine. I started with course compound and finished with fine.
If your valves are right you could finish the seats like I did. The factory seats are plenty hard,
not like some of the old cast iron v8 stuff. Just take your time.

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If the seats pitted, then it aint by much. I cant feel anything but a smooth surface if i run my finger nail over them. The valves are fine, no pitting or anything.

I'll try lapping them a little more. Thanks again.

Take a close look at those spots using a strong magnifying glass to see if they are pits or just discoloration. Ed

That head need's guide's and the seat's recut.
Look close the seat is wider on one side then the other.
Also look at the guide the hole is offset to the wide side of the seat.

pbmax wrote: If the seats pitted, then it aint by much. I cant feel anything but a smooth surface if i run my finger nail over them. The valves are fine, no pitting or anything.

I'll try lapping them a little more. Thanks again.

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Have they been machined?
If not they need to be done right in order for a lapping of the valves to work.
Or you will just be wasting time. The valve needs a smooth, straight surface.
Can you take a pic of the valve seat from a side veiw?

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79 kz750 twin, low miles

Sorry if the pics are too big. I'm doing this from my phone and cant rescale them .

Here's a side view.



Here's after more lapping. Looks better.



Nothing has been machined yet. Just carbon removal and lapping by me. I've seen pics of pitted seats and the pits are deep and visible. I dont see that in these pics. I plan on proceeding with a leak test and see how that goes. I know its not a perfect test for proper valve seating but its better than nothing.

Put the valve and spring back in and spray carb cleaner in the port
if any run's pass'd the valve it ain'f seating.

Post up some pictures of the Valves, showing where the contact patch is and the width. You want that as close to Center as possible, and within the spec for the width. For cheap Bluing Compound, you can mark the valve face with a Black Sharpie and then see where the contact area is.
You will more than likely need to re-shim, as you were probably already close to the min on clearance.