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Decked head 06 Nov 2019 06:24 #813624

  • SWest
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How much material can be removed from the surface of a KZ 1000 head and how can I tell if it's too much? The head is flat all along the surface area.
Steve

.002 moves freely

.003 is too tight
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Last edit: by SWest. Reason: add pics

Decked head 06 Nov 2019 12:14 #813637

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Whats your goal by decking the head? If you just need a fresh surface they will remove a few thousandths and it wont really effect things. If you are trying to raise compression you need to measure the combustion chambers before decking, then you can then roughly calculate how much to remove based on the compression increase you would like.
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Decked head 06 Nov 2019 12:51 #813638

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I believe the shop manual wants you to check diagonally across cylinder head to check for warpage

1972 H2 750 Cafe Racer built in 1974.
1976 KH400 Production Road Racer.
1979 Kz1000 MK. II Old AMA/WERA Superbike.
1986 RG500G 2 stroke terror.
1986 GSXR750RG The one with the clutch that rattles!

Up in the hills near Prescott, Az.
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Decked head 06 Nov 2019 14:15 #813642

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I suspect the head I'm working on has been decked. Maybe too much. That's why I ask.
Steve

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Decked head 06 Nov 2019 14:20 #813644

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you can measure the combustion chamber volume and compare it against stock. this is how its done>
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Decked head 06 Nov 2019 14:47 #813648

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I have seen them decked clear down to edge of valve W/O issues. in fact I do the drag bikes to get the quench down.
1984 750 Turbo
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Decked head 07 Nov 2019 04:11 #813664

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I saw a pic of a 900 head on this site where they just about cut into the fins.
1975 Z1 900
1994 KX250 Supermoto
2004 KX125

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Decked head 07 Nov 2019 11:24 #813680

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This is what I'm working with.
Steve

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Decked head 07 Nov 2019 15:42 #813691

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A KZ1000 head that has been decked 1mm will only have about a 3.8CC difference from stock, you need a piece of plexiglass held on with grease and a graduated cylinder to measure accurately. The surface tension of the fluid will make it impossible to check correctly without it

this is what i use

www.amazon.com/EISCO-Acrylic-Stopcock-Ca...id=1573170359&sr=1-3
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Last edit: by DoctoRot.

Decked head 07 Nov 2019 16:15 #813692

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That's OK. I found out what I needed to know. I'm going to modify the chambers like I was talking about. I'm more concerned about the voids filling with carbon then glowing causing detonation. If I lose a little compression so be it. Who knows, the engine may breath better. :whistle:
Steve

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Decked head 08 Nov 2019 08:30 #813712

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I took a snippet out of the video I did when I installed the APE head studs. It shows the pistons below the deck almost 2mm. I don't think I'll have any problems there.
Steve

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Decked head 08 Nov 2019 09:38 #813713

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SWest wrote: I took a snippet out of the video I did when I installed the APE head studs. It shows the pistons below the deck almost 2mm. I don't think I'll have any problems there.
Steve

If correct that is quite a lot .
Each 1mm of bore equates to around 4cc and an approximate compression loss of 2 points so you will be down substantially over stock depending on the pistons used.
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