TOPIC:

1985 GPZ750 and the whole bike is a mess, so I’m tearing everything down, including the engine to make sure it’s all to spec.

While apart I thought I would have a mild porting and milling of the head to get a little bit more performance. I don’t want it to be a racebike, but I do want it to have a bit more ooommph and set itself apart from the KZ750 and stock GPZ750. What can I do that will give me that and still allow it to be reliable and use pump gas?

just getting rid of sharp edges and blending of the ports will give you a boost. Not a big boost but careful work with a dremmel will work. Lap in the valve seat while your at it.

Milling? Be careful. Ed

Id would start by seeing how far down the highest piston is down the hole,then if theres any extra room to spare id pop the sleeves out then deck bottem of the cylinder if it was me anyway.
Id never deck a head any more than is required to make sure its flat,cylinders are a lot easier to space/shim or replace than a head if plans change in the future.
As far as porting the head,bigger isn't always betterVelocity is more important than large amounts of volume.

650ed wrote: Milling? Be careful. Ed

ED it's ok to mill a head you just need to stop right about here.

OMG

zukdave wrote:

650ed wrote: Milling? Be careful. Ed

ED it's ok to mill a head you just need to stop right about here.

So .003 off the head? Anyone else have anything to say about this amount?

taylee wrote: So .003 off the head? Anyone else have anything to say about this amount?

The valve seats are too close to the deck surface to allow milling such that you will increase compression. I'd have the head surfaced taking off the minimum amount of material possible to get a smooth surface and then stop there.

Gotcha. So you are talking the bottom of the cylinder head?

What of using a thinner head gasket? Are those available?

taylee wrote: Gotcha. So you are talking the bottom of the cylinder head?

What of using a thinner head gasket? Are those available?

Yes, the bottom of the head. Honestly, you don't need to mill it and I wouldn't, unless you have reason to question the quality of the sealing surface. Have your machine shop take a cleanup pass if you are concern about the sealing, otherwise I'd leave it alone.

Not sure about thinner head gaskets. I doubt you can make a meaningful change that way, other than you may get leaks.

Another option is to use three bond instead of a base gasket.


.

Nebr_Rex wrote: Another option is to use three bond instead of a base gasket.


.

Surely you jest. Right?