1987 KX500 Head mods for kyser777

[Sandblaster]

So, we are going to look at having a head cut and modified for a 1987 KX500.
kyser777, ask your questions

[kyser777]

Because the original kx500 86-87 piston has a dome shape and new type piston type (88-2004) is flat on the top.
the compression and the combustion chamber is altered with a new type flat piston.

any recommendations regarding the squish optimization.
do you know how to optimize the squish of this 87 kx500 head to match a flat piston?
how to shave and mill the head?

thanks

[Sandblaster]

What sort of fuel will you be running?
Are you wanting to get back to stock compression or are you looking to increase compression?
That will tell us what direction to go.

[kyser777]

where I am, the premium Gas is from 96 to 100 octan.
this is what I am using. I believe much better than the gas of 1987 they were using at the time.

I think the 86 kx500 stock compression was 8.5:1
given that a decompression valve will be fitted. 8.5:1, 8.6:1 sounds good figures
what do you think?

[Sandblaster]

Ok,,, Your country uses RON for rating octane whereas in the USA we use MON.
Here is a brief youtube vid explaining the differences:

https://www.youtube.com/watch?v=zf-OYXlhJis

I will do some more research this weekend.
Can you take some careful measurements?
IF so, when the piston is at top dead center, what is the distance from the top outside edge of the piston to the top deck of the cylinder?
And on the head, there is a "Step" depth... Can you measure that?

STEP HEIGHT.png (17.15 KiB) Viewed 10945 times

[kyser777]

Thanks for the octane unit lesson
So We Have likely RON 98 Gas where I am

PURE STOCK kx500 87 cylinder with B ART 89-2004 OEM piston and wrist pin:

Step = around 2.2mm
Distance from the top outside edge of the piston to the top deck of the cylinder = around 0.25mm

gaskets available:
-gasket 1.2mm cosmetic
-special OEM 11004-1185 GASKET-HEAD,T=0.2 | (OPTION) 88 steel gasket 0.2-0.25mm

thanks

[Sandblaster]

I need one more measurement.
What is the distance from the top of the exhaust port to the deck of the cylinder.
Thanks!

[kyser777]

the distance from the top of the exhaust port to the deck of the cylinder = around 50mm

thanks!

[Sandblaster]

Can you post a picture of the left side of your cylinder...
Something isn't adding up quite right...
Also a picture of the side view of your piston.
I want to see how much dome it has...

[kyser777]

the piston is a standard OEM piston 89-2004 , flat type.
what exactly do you want to investigate?

thanks