250-500cc Correct Orientation For Replacement Piston Rings?

[mr_manny]

I picked up some replacement rings online for my new-to-me wr250.

The issue is, there doesn't seem to be any sort of indicator for proper orientation.
The rings are flat, but do have a subtle twist to them.

Does the sharper edge face up towards the head, or down?
Thanks

 

[mr_manny]

​One side does have a sharper edge...but no marks visible



​

 

[mr_manny]

Found some markings...my mistake.
Since there are indeed markings, they represent the top-side?

 

[Picklito]

Yes. In every case I've ever seen, markings go up. They can be frustratingly difficult to see!

 

[mr_manny]

Thanks Picklito
Took a bit of finagling, but got the cylinder installed
Utilized a Dremel to trim the rings to .4mm

Got the idea from here:
​

View: https://www.youtube.com/watch?v=p7IDqc3YlHE

 

[Dirtdame]

Thanks Picklito
Took a bit of finagling, but got the cylinder installed
Utilized a Dremel to trim the rings to .4mm

Did you install the ring into the cylinder and measure the end gap? Was the end gap too small, or did you just remove material to help with installation?

 

[2premo]

Yes. In every case I've ever seen, markings go up. They can be frustratingly difficult to see!

what's easier is most if not all 2 smoke pistons have a dowel in the ring groove to keep the ring in the correct location so as to prevent ring ends from catching a port
so just use the index and it will also show you which way is up on the ring

 

[2premo]

Did you install the ring into the cylinder and measure the end gap? Was the end gap too small, or did you just remove material to help with installation?

if the piston ring is too tight it might not be the right one

 

[Dirtdame]

if the piston ring is too tight it might not be the right one

Exactly what I was thinking. End gap is the first thing I would check if I had trouble installing the piston assembly.

 

[2premo]

Thanks Picklito
Took a bit of finagling, but got the cylinder installed
Utilized a Dremel to trim the rings to .4mm

Got the idea from here:
​

View: https://www.youtube.com/watch?v=p7IDqc3YlHE

was this a 2 smoke ring you modified?????
the point at the outside of the ring is set to the cylinder diameter, the point on the inside is set for the dowel, did you correct both???

 

[mr_manny]

Did you install the ring into the cylinder and measure the end gap? Was the end gap too small, or did you just remove material to help with installation?

There was virtually no gap, as I ordered rings +.50, so they were tight.
All measurements were performed with the rings about 20mm into the cylinder with a feeler gauge.

 

[mr_manny]

was this a 2 smoke ring you modified?????
the point at the outside of the ring is set to the cylinder diameter, the point on the inside is set for the dowel, did you correct both???

I used Honda cr250 2 stroke rings.
I don't have an accurate bore gauge, so I ordered 66.5mm bore rings to play it safe.

There was enough room to clear the piston-ring grove dowel, so I didn't need to modify the inside (stepped) edge.

Now you have me worried there isn't going to be enough clearance for the piston grove dowel during heat expansion...

 

[Picklito]

Hmmm. I like the 0.4mm end gap. Might be worth checking the dowel gap. Air cooled motors do heat those rings! And too little gap can be a cause of new top end failure.

I give you Major Kudos, however, for asking the questions and wanting to get it right!

 

[Dirtdame]

I used Honda cr250 2 stroke rings.

Not sure I would use a ring that was not designed specifically for the bike brand and model. Rings are designed to work with a particular piston and even the engine characteristics. The ring radius may be different.

 

[mr_manny]

Since Honda and Husqvarna 250 2 strokes share the same cylinder bore, I didn't think it would be an issue.

I will keep everyone posted on my experiment with Honda piston-rings.

 

[2premo]

Since Honda and Husqvarna 250 2 strokes share the same cylinder bore, I didn't think it would be an issue.

I will keep everyone posted on my experiment with Honda piston-rings.

what year Honda rings and what year Husky?
early Honda was chrome and Husky was Nikasil
so totally different cylinder conditions

 

[2premo]

Not sure I would use a ring that was not designed specifically for the bike brand and model. Rings are designed to work with a particular piston and even the engine characteristics. The ring radius may be different.

as well as the cylinder coating

 

[mr_manny]

Very good points 2premo.
Thanks for the reply.

husky is an 07

Looks like 86-2004 Hondas have Nikasil coated bores.
I reached out to the seller asking which years the rings are designed for.

Keeping fingers crossed.

 

[2premo]

if the cylinder was Nikasil then you are good, they definitely used a different ring

 

[Dirtdame]

if the cylinder was Nikasil then you are good, they definitely used a different ring

Think about it though. The ring set was .50 over....so for a cylinder that can be bored.