TOPIC:

I was using my digital callipers to measure the width of my piston ring. The top ring and I'm getting 2.85mm. I'm not sure what the width spec is supposed to be. These are stock bore pistons.

FSM has the top and second rings at 1.17~1.19mm thick, with a service limit of 1.10mm.
Oil rings at 2.47~2.49 mm, service limit of 2.40 mm.

There are end gap (fig 90) measurements, but no width.

The Clymer service manual has a measurement for the ring's side clearance while installed, as measured in fig 93:

Top - 0.04-0.08mm, wear limit 0.15mm.
Second - 0.03-0.07mm, limit 0.15mm.
oil control - 0.02-0.06mm, limit 0.15mm.

rstnick wrote: FSM has the top and second rings at 1.17~1.19mm thick, with a service limit of 1.10mm.
Oil rings at 2.47~2.49 mm, service limit of 2.40 mm.

There are end gap (fig 90) measurements, but no width.

The Clymer service manual has a measurement for the ring's side clearance while installed, as measured in fig 93:

Top - 0.04-0.08mm, wear limit 0.15mm.
Second - 0.03-0.07mm, limit 0.15mm.
oil control - 0.02-0.06mm, limit 0.15mm.

Thanks. I also noticed when I was putting the bottom head piece back on to see how difficult it would be to get the pistons back into the cylinders it was pretty easy as if the rings didn't have enough tension on them?

blink543 wrote:

rstnick wrote: FSM has the top and second rings at 1.17~1.19mm thick, with a service limit of 1.10mm.
Oil rings at 2.47~2.49 mm, service limit of 2.40 mm.

There are end gap (fig 90) measurements, but no width.

The Clymer service manual has a measurement for the ring's side clearance while installed, as measured in fig 93:

Top - 0.04-0.08mm, wear limit 0.15mm.
Second - 0.03-0.07mm, limit 0.15mm.
oil control - 0.02-0.06mm, limit 0.15mm.

Thanks. I also noticed when I was putting the bottom head piece back on to see how difficult it would be to get the pistons back into the cylinders it was pretty easy as if the rings didn't have enough tension on them?

Can u explain the end gap specs? I would think 0.7 is larger than 0.15. Isn't 0.7=0,70mm? If the gap is wider wouldn't that be good cuz then to me it would seem the tension is better. I don't know much about piston ring wear. Obviously.

As the bore and ring wears the ring end gap increases (with the ring installed down into the cylinder), and compression can leak out through the gap. Not good.

If you take a used ring and a new ring and lay them on top of each other in the free state you will see that the gap in the new ring is wider by a fair bit (which is good). This is because the old ring has taken a set and lost tension.

When rebuilding a top end I use a bore gauge on the cylinder to judge wear, and I measure the pistons with a micrometer. If the taper and out of round in the bore is less than .001", and the piston to cylinder fit is .004" or tighter, you can reuse the cylinder and pistons. Use a 240 grit bottle brush hone and new Kawasaki rings and you'll be good to go.

Oh, and if you value oil tightness be sure to use OEM Kawasaki gaskets and seals. They cost more but are worth it. You can often get great prices on OEM gaskets on ebay.

Nessism wrote: As the bore and ring wears the ring end gap increases (with the ring installed down into the cylinder), and compression can leak out through the gap. Not good.

If you take a used ring and a new ring and lay them on top of each other in the free state you will see that the gap in the new ring is wider by a fair bit (which is good). This is because the old ring has taken a set and lost tension.

When rebuilding a top end I use a bore gauge on the cylinder to judge wear, and I measure the pistons with a micrometer. If the taper and out of round in the bore is less than .001", and the piston to cylinder fit is .004" or tighter, you can reuse the cylinder and pistons. Use a 240 grit bottle brush hone and new Kawasaki rings and you'll be good to go.

Oh, and if you value oil tightness be sure to use OEM Kawasaki gaskets and seals. They cost more but are worth it. You can often get great prices on OEM gaskets on ebay.

I might just take the cylinder head to a shop to get measured because I have no idea how to use one plus I don't want to get another special tool.

Nessism wrote: As the bore and ring wears the ring end gap increases (with the ring installed down into the cylinder), and compression can leak out through the gap. Not good.

If you take a used ring and a new ring and lay them on top of each other in the free state you will see that the gap in the new ring is wider by a fair bit (which is good). This is because the old ring has taken a set and lost tension.

When rebuilding a top end I use a bore gauge on the cylinder to judge wear, and I measure the pistons with a micrometer. If the taper and out of round in the bore is less than .001", and the piston to cylinder fit is .004" or tighter, you can reuse the cylinder and pistons. Use a 240 grit bottle brush hone and new Kawasaki rings and you'll be good to go.

Oh, and if you value oil tightness be sure to use OEM Kawasaki gaskets and seals. They cost more but are worth it. You can often get great prices on OEM gaskets on ebay.

Are telescopic gauges ok to use?

Of course, ....that's the way it has been done for years.... use a good set of mics and should be fine.

I'm gonna be pissed if it needs a bore job and bigger pistons. That's expensive

I've tried to use telescoping gauges before and really struggled with them. A bore gauge is MUCH more accurate and repeatable way to measure. That said, use what you got.

How many miles on this engine anyway? If it's less than 50k miles most likely the bores and pistons can be saved with new rings (assuming no scoring of course).

A good quick and dirty method to judge condition of the parts is to remove the rings from the pistons and then stick the piston down into the cylinder upside down from the top, and cut in a feeler gauge along the thrust face of the skirt. Measure about 3/4" down from the top of the bore since this is the point of max wear on the cylinder. Stick the feeler in next to the pin and then move it over to the thrust face. It's pretty common for the .003" feeler to go in fairly easily with some light drag, but a .004" feeler should be good and tight. If that's the case you can go forward with reusing the parts. If the .004" is loose then you have a problem.

Oh, and if you measure too much clearance go shopping on ebay for a low mileage cylinder. There were tens of thousands of 650's sold so it shouldn't be too hard to find a good stock cylinder. I've rebuilt several Japanese motorcycles and had to source cylinders and pistons this way and never had much trouble finding good parts. Target parts off a bike that has less than 20k miles and you should be fine.

Nessism wrote: I've tried to use telescoping gauges before and really struggled with them. A bore gauge is MUCH more accurate and repeatable way to measure. That said, use what you got.

How many miles on this engine anyway? If it's less than 50k miles most likely the bores and pistons can be saved with new rings (assuming no scoring of course).

A good quick and dirty method to judge condition of the parts is to remove the rings from the pistons and then stick the piston down into the cylinder upside down from the top, and cut in a feeler gauge along the thrust face of the skirt. Measure about 3/4" down from the top of the bore since this is the point of max wear on the cylinder. Stick the feeler in next to the pin and then move it over to the thrust face. It's pretty common for the .003" feeler to go in fairly easily with some light drag, but a .004" feeler should be good and tight. If that's the case you can go forward with reusing the parts. If the .004" is loose then you have a problem.

Oh, and if you measure too much clearance go shopping on ebay for a low mileage cylinder. There were tens of thousands of 650's sold so it shouldn't be too hard to find a good stock cylinder. I've rebuilt several Japanese motorcycles and had to source cylinders and pistons this way and never had much trouble finding good parts. Target parts off a bike that has less than 20k miles and you should be fine.

There's about 30,000 miles on this engine. And ok I'll try this. The cylinders do look very smooth still and not scored

blink543 wrote:

Nessism wrote: I've tried to use telescoping gauges before and really struggled with them. A bore gauge is MUCH more accurate and repeatable way to measure. That said, use what you got.

How many miles on this engine anyway? If it's less than 50k miles most likely the bores and pistons can be saved with new rings (assuming no scoring of course).

A good quick and dirty method to judge condition of the parts is to remove the rings from the pistons and then stick the piston down into the cylinder upside down from the top, and cut in a feeler gauge along the thrust face of the skirt. Measure about 3/4" down from the top of the bore since this is the point of max wear on the cylinder. Stick the feeler in next to the pin and then move it over to the thrust face. It's pretty common for the .003" feeler to go in fairly easily with some light drag, but a .004" feeler should be good and tight. If that's the case you can go forward with reusing the parts. If the .004" is loose then you have a problem.

Oh, and if you measure too much clearance go shopping on ebay for a low mileage cylinder. There were tens of thousands of 650's sold so it shouldn't be too hard to find a good stock cylinder. I've rebuilt several Japanese motorcycles and had to source cylinders and pistons this way and never had much trouble finding good parts. Target parts off a bike that has less than 20k miles and you should be fine.

There's about 30,000 miles on this engine. And ok I'll try this. The cylinders do look very smooth still and not scored

.004 wouldn't go in .003 wouldn't go in but .002 was a fit. So is that good? It's pretty tight.