There are two different
KZ1000 engines. The first is the Z1 type which was built between
1976 and 1980. The second is the 1000J, or "J model"
as it is called, and was built from 1981 until present ( currently
only available in police motorcycles). These engines are different,
but some of the parts can be interchanged, and this has caused
much confusion. We hope this makes everything clearer.
The first example is simply
a big bore Z1 900. This engine came with a kick starter and electric
starter. The cam
chain tensioner hole in the cylinder block is a rectangle. The ccs cast on the
cylinder is 1015. The later "J model" has no kick starter,
and the cam chain tensioner hole in the cylinder block is round.
The cc's cast on the cylinder is 998. This engine also became
the GPZ1100 in 1981 and '82, and virtually everything between
them is the same. (The '83-'84 GPZ1100 was changed). Cylinder
blocks and lower engine cases are NOT interchangeable. You can
not put a J model cylinder on an older style lower end, and vise
blocks.. Not interchangeable.
If you have a J model block/GPZ1100 block you must use a J model
or GPZ1100 cases.
Crankshafts... Early KZ1000
used a roller
type cam chain and the crank has that style center sprocket. J model used Hy-vo
style chain. J model cranks can be used in early lower end if
the center crank pin is changed to one with a roller chain sprocket.
The J model connecting rods are approx 1.2 mm shorter than early
Cylinder head.. J model
head has larger valves and ports. This head can be used on earlier
style cylinder and lower end by installing APE #CCIA cam chain sprocket
adapter in head
. How to tell which head you have.. Early style heads have four
factory drilled and tapped 6mm holes in the center to bolt in
cam chain idler gear. Z1 900 heads have 6 mm exhaust studs, KZ1000
8 mm. On the J model head, the four cam plugs at the ends of the camshaft areas
are bolted in, on the early style head, they just push in and
the valve cover holds them in. The J model / '81-'82 GPZ1100
cylinder head has a larger combustion chamber than the early
style head. When these heads are used on the early style motor,
a compression ratio drop of about 2 full points can be expected.
Pistons... All pistons
have 17 mm pin holes, but the J
model/ '81-'82 GPZ1100 pistons have the pin hole lower in the piston to make
up for the short connecting rod. All J model and early '81-'82
GPZ1100 pistons are the same ( '83-'84 GPZ has 18 mm pins ) Therefore
any '81-'82 GPZ piston can be fitted to a J model engine to make
a big bore engine. Pistons for the J model / '81-'82 GPZ1100
can not be used in a motor that has an early style long connecting
rods unless a spacer plate is used under the cylinder block to
compensate. If early style KZ
pistons are used
in an engine that has the short J model / '81-'82 GPZ1100 connecting
rods, a special short cylinder block has to be used.
We have tried to make this
as clear as possible. When ordering your parts from APE, let
us know which engine you have, or if you are mixing early style
and late style parts, let our tech/order department know and
we will see to it that you get the correct parts combination.