[VALVES SEATS] Should they be cut ?

Hello,

When working on my KZ1000ST engine this week-end, I notice the valve seats are quite strange :



The width isn't the same all around the seat. Moreover, on some valves, the seat width is (on some places, since it changes all around the seat) 2.3mm! It's written in the manual it should be between 0.8mm and 1.2mm.
Do you think I should get the valve seats cut and the valves replaced?
BTW, here's a valves before/after cleaning :




Thanks for the help.
Nicolas.

yeah id have the seats and valves ground as long as its apart,and check the guides and springs amd throw new seals in there;)

wireman wrote:

yeah id have the seats and valves ground as long as its apart,and check the guides and springs amd throw new seals in there;)

I'll have to say goodbye to some $$$ then... :S

The fact that the seats width isn't the same all around the seat is quite strange. Are the seats not perfectly in the direction of the guides?

How will the guy who will ground the seats and valve know how far he has to grind down the valves? I'm worrying about the shims height...

As regards to the springs, I measured their length, but I didn't find any reference to that in the manual.

Does anyone know what length they should be?

Actually, there's nothing strange about the valve seat condition. That's normal wear.

Seals are definitely shot and guides may be worn out.

That head is in definite need of a valve job. The valves look like good candidates for refacing the 45 and adding a narrow 30 degree back cut.

Performance is gained through a good valve job, even if no additional port work is done. At least you get the motor freshened to factory spec.

Post edited by: larrycavan, at: 2007/05/01 20:28

Conti wrote:

How will the guy who will ground the seats and valve know how far he has to grind down the valves? I'm worrying about the shims height...

Depending on the shim sizes you have in there now, you may want to consider getting the valve stems ground a bit to recover some clearance. If your shims are already down in the <220 range, I'd definitely do the stems.

Be sure to check your manual for the specs on this. It should tell you the maximum amount of stem to grind off.

Post edited by: Skyman, at: 2007/05/01 19:51

Be careful! Let whoever is doing the valve job take care of tipping the valves as well.

Is refacing a "must"? I mean, can that wait, or do I have to do it right now to avoid any further damage?

The exhaust camshaft isn't a normal one. Look at this thread .
The cam heights are 36.27mm while they should be between 35.71 and 35.89mm! I assume the figures written in the manual won't be very useful for the person doing the refacing. Should I bring the camshafts too, to the guy doing that work?

Thanks.

Those seats are pitted. It will be a leaker if not repaired. The guides are probably shot with that much junk on the valve.

Don't take that head to an automotive shop. Take it to someone who known these motorcycle heads.

When you get it back, bench shim it before you install it. If you have a valve that is too tight, best to find out before you waste a head gasket.

We sell a simple $15.00 gage that is used to check stem height after valve jobs.

Jay

Seats look like a recut is in order and recutting will for sure alter stem height.

My 1981-85 J manual says stem height fitted should not exceed 38.3mm. If it does the stem tip should be ground down but no more than necessary. It says the distance between stem top and collet groove should not be less than 4.2mm

The moral is take out the least meat from the seats as possible.

If thes tolerances are not achieved it may mean new seats

seat angles from outer should be 60deg, 45 deg, 30 deg with a 1.00mm seat width

Kiwiz wrote:

Seats look like a recut is in order and recutting will for sure alter stem height.

My 1981-85 J manual says stem height fitted should not exceed 38.3mm. If it does the stem tip should be ground down but no more than necessary. It says the distance between stem top and collet groove should not be less than 4.2mm

The moral is take out the least meat from the seats as possible.

If thes tolerances are not achieved it may mean new seats

seat angles from outer should be 60deg, 45 deg, 30 deg with a 1.00mm seat width

New seats? I thought the seats can't be removed.

BTW, what about the seat you see on the picture? Do you think it was already cut?

As regards to the angles, I was surprised to notice the shape of the pit:


It looks like it's a 90° angle!?! :blink:

Sure the seats can be replaced, that's why APE sells replacement and oversize valve seats (for oversize valves).

The seats don't need to be replaced. They just need to be re-cut. When you re-cut the seats, if the valve faces are in pretty good shape [not in need of new valves] then they get refaced on the valve machine.

When you recut the 45 seat angle, it sinks the valve and widens the seat. The inside cut narrows the seat back to optimal width and the outside cut locates the seat properly on the valve face.

Generally on the exhaust valves, the factory only shallow cut the seats and they reall could use sinking anyway.

New seats are generally reserved for oversize valve installation beyone 37.5mm intake valve size in a KZ head unless there's such wear or severe enough damage to require seat replacement.