Installed Ring Gap

This is a stock '84-> GPz550 engine, with standard bore pistons and rings.

Looking in my factory supplement manual for the '84->, it doesn't state the piston ring gap as installed in the cylinders. It does show it for the ZR550, which should be the same as a KZ550 I believe??? The top and second installed ring gap should be 0.15-0.30mm( .006-.011" ) With a Wear Limit of 0.6mm( 0.023" ). None for the oil rings obviously. Is there a "rule of thumb" to ring gap and bore size?

In another manual I have, it states no installed ring end gap for the '84->(A1-A3), but it states it gap for KZ550-F1, M1.



I'm getting set to gap the rings for the head I've surface-honed a month back, as the standard rings have finally come in.



Here's the spec's on the used pistons I have:

Piston Ring Groove Thickness Information ZR550/KZ550:
Top 1.21-1.23mm(0.047-0.048" ), Wear Limit 1.131mm(0.051" )
2nd 1.23-1.25mm( 0.048-0.049" ), Wear Limit 1.33mm(0.052" )
Oil 2.51-2.53mm( 0.098-0.099" ), Wear Limit 2.61mm( 0.1027" )

Actual Piston Groove ReadingsGPz550:
Top and 2nd 1.207mm( .0475" )
Oil 2.438mm( .095" )

The Piston Grooves seem to be within the service limit, but it's the ring gap I'm worried about. Not too big, and not too small. Anyone think the above listed gap should be OK? Right out of the box, the top and second ring installed gap measure within the above recommendations.

Pictures? You bet!!!


Rings in the bore about 1/2 way down. Can you see the "T" Stamp?



Tiny "T" for top, barely visible just to the left of the gap:


Ain't no way I'm missing the "T", so I've highlighted them all:


Not a trick question, but which one is the compression ring, and which one is the second ring? They are both are the same thickness of 1.168mm( 0.046" ).

Any input would be greatly apreciateded. Thank you.

as a general rule of thumb. .007 per inch, but that is on a automotive engine, I have not looked at the specs on the bikes in a long time.
If you are using stock rings with rehoned bores, then they are prob going to be on the larger side , wear in the cyls and material honed,
The ring you show on the top, is the top ring.
also dont forget to check the wear in the piston ring land area

Thanks for the information.


As you can see, the ring land area is very good. These pictons have very low mileage on them, and look to be in excellent condition with very little wear.

CoreyClough wrote:

This is a stock '84-> GPz550 engine, with standard bore pistons and rings.

Looking in my factory supplement manual for the '84->, it doesn't state the piston ring gap as installed in the cylinders. It does show it for the ZR550, which should be the same as a KZ550 I believe??? The top and second installed ring gap should be 0.15-0.30mm( .006-.011" ) With a Wear Limit of 0.6mm( 0.023" ). None for the oil rings obviously. Is there a "rule of thumb" to ring gap and bore size?

YES, and here it is:

ring end gap should be about .003" - .004" (nominal) PER INCH OF PISTON DIAMETER.

3" diameter piston: .009" - .012" (nominal)

my manual also says the service limit is about twice the nominal value.

CoreyClough wrote:

Not a trick question, but which one is the compression ring, and which one is the second ring? They are both are the same thickness of 1.168mm( 0.046" ).

The ring with no grooves is the top ring. The one with the grooved lip is second, lip goes downward.

The bore is 58 millimeter = 2.283" .



There aren't any cut-outs, or odd shape on either of the rings. Just what you see there. They are both the same thickness top to bottom, and inside to outside.

Maybe your top two compression rings are both the same. They are different on my 750, maybe not on your pistons?

On www.GPz550.com , I've posted the same story, and a new member has given this link to read through:
www.riken.co.jp/e/piston/b/b_2.html

I do think you are right about the top ring being the one having the "special" edge. I don't have the rings that came off of these pistons, as that might help too.

Yes, interesting the piston ring groove, and the rings are exactly the same for the top and bottom, dimension-wise. I would think Kawasaki would state which ring goes on top, by maknig a 1 or a 2 next to the "T" stating the correct placement.

Thanks again for your replies.

NOTE*** Looking at the picture above, the darker ring, deemed the 2nd ring, has a bigger free gap than the one you stated is the top ring.

look very closely at the outer edge of the rings and see if they are exactly square or if 1 has a taper.
offten the second ring sometimes has a slight taper.

In the picture above, the darker colored ring has very sharp edges all around, while the lighter color ring with the silver edge doesn't have near as sharp of edges. Would that darker one be the top ring? It has to make a difference where they go on the piston.

Someone has got to know for sure which ring goes on top, and which goes in the 2nd position.

THE TOP RING IS THE CHROME ONE THE SECOND RING IS THE CAST RING[THE DARKER ONE] RING END GAP IS .003 PER INCH OF BORE I.D MARKS GO TO THE TOP. THE RINGS SHOULD BE INSTALLED SO THAT THEIR GAPS ARE 120 DEGREES APART, SOMETIMES THE CHROME RING WON'T HAVE ANY MARKS IF IT DOESN'T THEN YOU CAN INSTALL THE RING EITHER WAY.THE TOP RING IS THE COMPRESSION RING THE SECOND RING IS THE SCRAPER RING.THE SECOND RING WILL ALWAYS HAVE A SHARP EDGE TO IT . IF YOUR NOT SURE OF ANYTHING ELSE YOU CAN E-MAIL ME DIRECTLY I'M A LICENSED MOTOR CYCLE MECHANIC AND I ALSO TEACH MOTORCYCLE MECHANICS AT FAIRVIEW COLLEGE

Thanks, I had a hunch. That's the information I was looking for, and I'm saddened that Kawasaki doesn't state that in the facxtory manual. Now I know.

Like Chris Farley said on Tommy Boy,"If you want to get a good look at a T-Bone you could stick your head up the bull's a$$, or you could just take the butcher's word for it."