OEM Piston code question

When looking at online catalogs for pistons for an 82 1100, there seem to be two or three types of Kawasaki OEM pistons listed:

1. SKU: 13001-1118
PISTON-ENGINE,STD

2. SKU: 13027-1055
PISTON-ENGINE LL,0/S

I would expect O/S to indicate OverSize. But I don't know how much oversize they would be. Does anyone know the answer?

My local Kawasaki parts guy didn't know.

Thanks,

Kirk P.

I just bought a set of L,O/S pistons for my 1981 KZ1100A1. The pistons are marked "50" on top. The catalog lists LL,O/S also. I can't remember where I heard it but I think L,O/S is first oversize and LL,O/S is second oversize. One of my old pistons measures 71.85 mm and one of the new ones measures 72.30. It may be that the first oversize is .50 mm bigger than stock and the second oversize pistons are 1.0 mm bigger.

The machinist who did the work on my cylinders said that first oversize is sometimes barely enough to clean up the cylinders and second oversize would be better. There are a lot of guys on this forum who know a lot about this (like APE Jay) so I'm sure you'll hear from an expert.

oversize oem pistons are usually stamped .25, .50, .75 and 1.0 As stated above, these are MM. So they are basically .010" increments.

13027-1055 is second oversize (+1mm),from Kawasaki not more avaliable.

Thanks fellows!

If my OpenOffice skills are right, then the following displacement values correspond to first over, second over...

(For KZ1100 only)

Overbore

---

Bore

---

Stroke

---

Displacement
stock

---

72.5000

---

66

---

1089.86
first

---

72.7540

---

66

---

1097.51
second

---

73.0080

---

66

---

1105.18
third

---

73.2620

---

66

---

1112.89
fourth

---

73.5160

---

66

---

1120.62

Sorry about the

---

but I couldn't make spaces stay in place to align the columns.

Kawasaki made only three pistons for these bikes

std. = 72,5mm

1st oversize = 73mm

2nd oversize = 73,5mm

no name wrote:

Kawasaki made only three pistons for these bikes

std. = 72,5mm

1st oversize = 73mm

2nd oversize = 73,5mm

So they should be .5 , 1. , and 1.5 markings

first oversize is 0.50,second is 1.00.

the piston on this picture is 2nd oversize from a GPZ 1100 B2 ...

Here's a first oversize for a 1981 KZ1100A1. Part No. 13029-1057, L/OS:

no name wrote:

first oversize is 0.50,second is 1.00.

the piston on this picture is 2nd oversize from a GPZ 1100 B2 ...

Thought I would note the piston code for this:
13027-5001

KP

Beware of using the terminology "first over" and "second over";

Kawi makes two sizes over which are +0.5mm and +1.0mm, so their first over is +0.50. However, some aftermarket pistons for Kawi come in oversizes in 0.25mm increments so their first over is +0.25mm.

That's why they stamp the number on top of the piston.

to be safe id just go with the 1170 and be done with it! :laugh: