1986 vs 1987 head

[sawfly]

will an '87 head fit an '86 bike? i'm having trouble finding an '86 head and someone mentioned that the 86-88 heads will work but the PN's are different.

[mun]

You can use 86-88 cylinder heads and cylinders with each other.

I do not remember whether the various year models of cylinder heads volumes of small differences, but it does not matter if you drive a standard motor. However, the tuned engine you make changes to the cylinder head.
87-88 cylinders an additional exhaust ports a recess to facilitate the start-up. Otherwise, the ports are almost the same.
1986-88 cylinders exhaust ports adjustment is only an additional ports.

Was fairly difficult to translate into English. I hope you understand this.

[RoostDaddy]

86/87 heads will fit each other. I believe if you want to use an 88 you may need to change the head studs as they are different. If memory serves me 86/87 were shouldered studs 88 isn't. Hopefully somebody with more knowledge of the older style motors will chime in to confirm.

[mun]

RoostDaddy, you're right.
The cylinder head studs must be replaced, or can also to machine 88-cylinder head the recesses.

1986-87 KX500 cyl head_b by MuN52, on Flickr
1988 KX500 cyl head by MuN52, on Flickr

[motopunk]

RoostDaddy, you're right.
The cylinder head studs must be replaced, or can also to machine 88-cylinder head the recesses.

1986-87 KX500 cyl head_b by MuN52, on Flickr
1988 KX500 cyl head by MuN52, on Flickr

... but that is an easy to made machining to fit
the 88 head to the 86/87 cylinder . could be made carefully with a drilling-machine ... 

but as long to the other diferences..  86 and 87 head are complete the same. the 88 has a diferent squish for the 88-2004 2ring-piston and is designed for lower compression.  86 and 87 had single ring flat top pistons..