piston ring staggering? help?!?!?

hey guys, so i was going to install the cylinder yesterday and noticed in the manual that the rings need to be staggered in a certain arrangement, the picture of how to stagger the rings makes absolutly no sense! for those of you with clymers manual, (2001-2003 wr250) its on pg 144, chapter 4, engine top end, figure 101.

heres the pic from the manual



Think of it this way:

The wrist pin goes horizontally. Do Not line up the ring gaps directly in line with the wrist pin, no matter what.

Clock the top ring at about 2:00

Clock the middle ring at about 8:00

Clock the oil rings at about 10:00

Do that and you will be good to go.

4 stroke rings are not pinned like 2 stroke rings, so they can move, but its been my experinece that they do not move around much. They are free to move, but don't.

If the ring gaps are lined up with the wrist pin, then you can expect oil consumption to increase, so that is the reason not to line them up that way.

You place adjacent ring gaps as close to 180 degrees appart for the top 2 to help contain compression. If the gases have to go all the way around to the other side of the piston to escape, they won't. If they are lined up and can travel straight down, they will, and you will burn the piston at that spot and ruin it.

Good luck. I've done it this way for years and not had any probs.

On a 4 stroke it is not as important to arrange the rings as it is on a 2 stroke. On a 4 stroke they just don't want the gap in the rings to be in the same line. I am assuming by the picture it means that the ring gaps should be 45 degrees from each other but i could be wrong on that one.

thanks guys! i called yamaha to be sure, and it explained the diagram above, top ring was at 11 (12 being intake side) middle at 5, then top oil ring at 7, middle oil ring at 5, bottom at 11, all being 90*-180* apart

Yeah, on 4 stoke engines, the rings actually rotate while the engine is running. At 5,000 RPM crank, the rings may be rotating about 10 RPM. The reason to offset the ring gaps on assembly, is to avoid having any gaps lined up, that will increase blow by for the first few min after startup. Since each ring rotates in it's grove at a slightly different RPM, the gaps actually align for a few revs occasionally, with no noticable effect. The two rails of the oil scraper ring and the expander band all rotate as one together however, so offsetting the scraper rails correctly is really important.

John, if that's the case, why is it that when I tear down my engines, I find the find the ring gaps exactly where I placed them at buildup?

If the rings did not rotate, then there would be less wear on the cylinder wall where the ring gaps are at, with narrow marks on the cylinder wall, for each ring gap, And, the rings would stick in the groves easily as well. I don't know why your ring gaps seem to be staying in the same places, relative to the other ring gaps and piston, but I believe that is very unlikely. If that was really happening, it would be a malfunction of the piston rings. Rings don't necessarily rotate at the same speed, or even in the same direction all the time. As the engine load varies, and the crank RPM varies, the rings rotation speed changes, and stops then rotating in the other direction at certain speed/load points. The first and second compression rings rotate independently, the oil scraper ring rotates a lot less than the 2 compression rings due to the two scraper rails that make up the 3rd oil scraper ring.

Yeah, I thought the same thing that they never rotated until I recorded where they were when I installed them, and where they were 20 hours later at a ring change. They actually do rotate at a rate of about 1/1000 rpm. 2 stroke's have to have their rings pinned to stop them from rotating and catching a port. 4 strokes have no ports to catch so they are allowed to float freely essentially.

It's one of those things that you have to see to believe.

But to the original poster:

For 2 ring pistons I configure them like this: 12o'clock being the center of the intake

Top ring: 9 o'clock (parallel to the piston pin)

2nd ring: 3 o'clock (parallel to the piston pin)

Oil rails: 5 and 7 o'clock

oil ring expander: 12 o'clock

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