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post #1 of 7 (permalink) Old 09-13-2015, 10:50 PM Thread Starter
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Pistons

So I got to looking at parts diagrams and there was 3 different piston types listed. Anyone have info about the differences? (I've searched the forums with no results.)

PISTON-ENGINE,STD
13001-1215
http://www.kawasakipartshouse.com/oe...ton-engine-std

PISTON-ENGINE L,O/S,0.50
13029-1128
http://www.kawasakipartshouse.com/oe...ine-l-o-s-0-50

PISTON-ENGINE LL,O/S,1.00
13027-1128
http://www.kawasakipartshouse.com/oe...ne-ll-o-s-1-00
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post #2 of 7 (permalink) Old 09-13-2015, 11:00 PM
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Quote:
Originally Posted by MikeTastic View Post
So I got to looking at parts diagrams and there was 3 different piston types listed. Anyone have info about the differences? (I've searched the forums with no results.)

PISTON-ENGINE,STD13001-1215
http://www.kawasakipartshouse.com/oe...ton-engine-std

PISTON-ENGINE L,O/S,0.5013029-1128
http://www.kawasakipartshouse.com/oe...ine-l-o-s-0-50

PISTON-ENGINE LL,O/S,1.00
13027-1128
http://www.kawasakipartshouse.com/oe...ne-ll-o-s-1-00
My best guess is the first one is standard OEM diameter.
The second is oversize 0.50 mm (about 20 thousands of an inch)
The third is oversize 1.00 mm (~40/1000s)

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post #3 of 7 (permalink) Old 09-13-2015, 11:47 PM Thread Starter
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That's what I was thinking. So that being said, naturally a bigger piston would mean more power right? And if it's listed in the oem diagram, it should work with stock cylinder?
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post #4 of 7 (permalink) Old 09-14-2015, 12:00 AM
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If piston is. 50mm or 1.00mm then cylinder needs to be bored out accordingly.not sure if the bores on our bikes are nikasil coated or not

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post #5 of 7 (permalink) Old 09-14-2015, 08:48 AM
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correct on all above.

they list different sizes from the factory, as not all get out of the machining process at the design spec (oem). some end up larger, and they fit larger at the factory.

amount of power gain from larger piston/bore (taking 1 mm here), not a lot, probably not even really measurable. Most of the gain would be seen from the new surfaces, which would seal better with the rings (which would also need to be replaced with appropriate size).

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post #6 of 7 (permalink) Old 09-14-2015, 08:54 AM
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Quote:
Originally Posted by MikeTastic View Post
That's what I was thinking. So that being said, naturally a bigger piston would mean more power right? And if it's listed in the oem diagram, it should work with stock cylinder?
Yes...a BIGGER piston would mean more power, but you're not really going that big by increasing it 20/1000 of an inch. I know even on a four cylinder motor going up a piston size only gives you more power if the previous piston and rings were giving you poor compression. Going from 748cc to 752cc won't be much of an increase.
(I think the VN's bore is 84.9 (stroke a 66.2) which works out to about 749cc's...if you went to a 85.0 bore that only give you 2 more cc's...751)
When they say going bigger gives you more HP, they mean going from 750cc to like 900cc....or more.

If you're getting good compression and not burning oil there's no reason to put in "bigger" pistons. These bikes should go 50-75,000 miles before there is a need to do that.

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Last edited by Knifemaker; 09-14-2015 at 09:06 AM.
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post #7 of 7 (permalink) Old 09-15-2015, 11:00 AM
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ok time for the engine rebuild guru to step in... before you order your pistons, get the cylinder work done... Meaning hone the cylinder walls first and then measure the run out of the cylinder walls. Once you do that, you will know if a standard piston will fit back in, (9 time out of 10 it will) or not. The performance engine builders bore out 0.030" to 0.060" over spec and then adjust the rod length to gain a longer stroke which nets higher compression and larger displacements. Unfortunately on the VN750 with out a lot of work and access to a milling machine you can't stroke the engine, just bore it out which is not going to net you any significant HP or TQ gains alone. The only reason the parts book shows three sizes of pistons is to accommodate cylinder wall wear over time.
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