Replacement Head / New Seats?

[Speedie]

Hello All! Discovered today that the head on my project bike (Z1000A1 with a 900 head) is pretty much scrap....its bad! one or two shims down to 2.00 and on removing the valves it looks like all tips and some collets have been tipped on a grinding wheel, the seats are worn and pitted and its generally been butchered, it looks like its been thrown together by a 3 year old, its grim! There's more damage I could mention, but you get the picture

So I need to source a replacement head and I'm thinking that anything has to be better than what I currently have. If I can find a half decent non butchered one it would be a good start. No doubt the seats on a 46 year old replacement head are going to be suspect, so my question is: Is it possible to get new valve seats inserted? I appreciate it will be expensive. I have seen an option of oversize valves mentioned on the forum, but I don't really understand what that is all about. (I would rather keep things standard if it comes to it, unless someone can convince me otherwise)

Obviously I need to get a replacement head first and see how it checks out, but does anyone have any thoughts or experience on getting new seats fitted, Is it feasible any recommendations?
I did a few searches but nothing has come up.

Many Thanks
Paul

[zed1015]

If the stock valves are sunk too far then fitting oversize ones is the usual cure.
These will use the wider diameter uncut portion of the seats and regain maximum valve clearances.
Worn seats is the main reason many heads have oversize valves and not for any tuning purposes.
Failing that new seats can be fitted too to allow new stock valves to be installed.
In the correct hands though the head in it's current state may be able to be salvaged with just some minor machine work to the valves, collets and retainers.
Up to 1mm can be removed from the collets and retainers and 1.3mm from the stock valve stem which usually brings the shim sizes back toward the 3mm range.
Also another popular option is to fit Z1000J valves as these have 1mm shorter stems and will enable you to regain the lost clearance.

[Speedie]

Thanks Rob
Fantastic knowledge and information as always.
Plenty for me to think about. All may not be lost.
I need to speak to Buzzworkz or Debben.

Paul

[Skid Mark]

If the stock valves are sunk too far then fitting oversize ones is the usual cure.
These will use the wider diameter uncut portion of the seats and regain maximum valve clearances.
Worn seats is the main reason many heads have oversize valves and not for any tuning purposes.
Failing that new seats can be fitted too to allow new stock valves to be installed.
In the correct hands though the head in it's current state may be able to be salvaged with just some minor machine work to the valves, collets and retainers.
Up to 1mm can be removed from the collets and retainers and 1.3mm from the stock valve stem which usually brings the shim sizes back toward the 3mm range.
Also another popular option is to fit Z1000J valves as these have 1mm shorter stems and will enable you to regain the lost clearance.

I've been off line most of the summer and only catching up on post now. I know this tread is going back a bit.
If J valves are 1mm shorter than the 1000A or 900 valves, can the J also be shortened upto 1.3mm in a J head or are they tied into the 0.3mm max recommended in the service manual?

[zed1015]

I've been off line most of the summer and only catching up on post now. I know this tread is going back a bit.
If J valves are 1mm shorter than the 1000A or 900 valves, can the J also be shortened upto 1.3mm in a J head or are they tied into the 0.3mm max recommended in the service manual?

Yes! they can be shortened the same.
I've just done exactly that with a J head and some details are in my latest project thread.