79 kz400 Cylinder head and bore size question.

Bike is a 79 kz400 ltd. So I found a pair of .75 over bore pistons for 74-79 kz400 on ebay would these fit my engine? Or maybe the engine I will buy off someone I met on here it's a 78 kz400 b1? Just curious as other oprions to try over the winter. I do know will have to bore one set of cylinders out just curious which would be better. Will a 78 kz400 b2 head and cylinder set up fit my engine? Spare me the bike bandit and partzilla diagram hunt lol

If memory serves there is no difference between the '79 KZ400 LTD engine and the '78 KZ400B2 engine.

Both engines will have the hard oil line (with banjo fittings) running from the oil pressure switch mount to the top of the head, so there shouldn't be any issues in swapping heads, if that turns out to be necessary.

Awesome thank you. I'm going to look for a much smaller bore size like .020 or .040 but was curious about the big size because well why not lol.

Are your piston and cylinder shot or have low compression?
Anyway for this price i would do it to get some backup parts.
Honing the cylinder will be the expensive part if doing professional.

No eBay APP ID and/or Cert ID defined in Kunena configuration.75 inch overbore seems like a lot when first overbore is .020 inches and second is .040 inches. I see that they are marked as .75 on the top of the pistons, I wonder if that is mm instead of inches which would equate to about .029 inches. My other concern is with that part number, 13027-063 - which is supposed to be the 2nd overbore pistons .040. If you look at other pics for that part number they are round top pistons, the ones in that pic do not look the same, they are flat top. I suspect they are either an aftermarket piston for the KZ400 or they are for something else. Seller says they are "new in the box", I would ask for pics of the box to look at the markings to try to identify what they are. If the box is an NOS Kawasaki box for 13027-063 ( you can see one in this listing ) then I'd be concernced that someone stuck different pistons in the Kawasaki boxes.

No eBay APP ID and/or Cert ID defined in Kunena configurationNo eBay APP ID and/or Cert ID defined in Kunena configurationNo eBay APP ID and/or Cert ID defined in Kunena configurationWell apparently there were flat top pistons too, different part number:







The last one shows that .075mm = .030" overbore. That's a new one on me. The parts listings I have seen list .020" and .040" overbore pistons along with the standard size but none show a .030", but apparently Kawasaki did make them. So the ones in your original ebay listing appear to be valid but maybe wrong part number?

If either engine you are considering has the stock pistons and you think they need new pistons and rings then as you suggested I'd try to find .020" oversized first but the .030" could be an option and at a nice price with pistons and rings. Be careful with those rings though, it tough to find .020" and .040" rings, I don't know that you'd ever find another set of .030" rings.

No eBay APP ID and/or Cert ID defined in Kunena configurationNo eBay APP ID and/or Cert ID defined in Kunena configurationNo eBay APP ID and/or Cert ID defined in Kunena configuration

diggerdanh wrote: Well apparently there were flat top pistons too, different part number:







The last one shows that .075 = .030 overbore. That's a new one on me. The parts listings I have seen list .020 and .040 overbore pistons along with the standard size but none show a .030, but apparently Kawasaki did make them. So the ones in your original ebay listing appear to be valid but maybe wrong part number?

If either engine you are considering has the stock pistons and you think they need new pistons and rings then as you suggested I'd try to find .020 oversized first but the .030 could be an option and at a nice price with pistons and rings. Be careful with those rings though, it tough to find .020 and .040 rings, I don't know that you'd ever find another set of .030 rings.

HAHAHAHA LOL LOL
Sorry Dan, but the piston oversize goes by mm.
.75 means 3/4 of 1 mm.
1 mm is .03937 of an inch.
And those pistons are for an early KZ400.
They are dome pistons and the tops are flat.
The late KZ400 pistons look like the most of the rest of the KZ line, a rounded dome.


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Yeah, most of the parts listings show the overbore in inches .020 and .040 though I knew that Kawasaki also spec'd them in mm. So I suspected the .75 on the piston top was mm not inches . But I was mostly confused by the part number of the original ebay listing that was showing the flat topped piston ( flat topped dome, you're correct ) when other pistons with that part number show full domed pistons, so I think something is incorrect with that listing. The "that's a new one on me" part was in reference to a .030" overbore, I had never seen that, only .020" and .040".

Additionally my failure to include mm and inch qualifications in my numbers in that post probably didn't help it read very coherently. I'm not crazy, I promise!