fun with rings.

[Crazcnuk]

I am trying to rebuild the top end of the G, and I have a question for the ring experts.

I have checked the end gap of some new rings, std size, and they are just slightly out of spec.

The max for an 80 is .016, and i am getting .018. The rings that came out were .084.

I have 2 sets of 1st over rings, and if I put them in, they overlap, of course as they are slightly too big.

Do you think I would be able to use 1st over rings on std pistons if I file for the end gap, or would I be better off using stock rings slightly out of spec?

I have 2 sets of 1st over and 1 set std, so i need one more set either way.

[oseaghdha]

I wouldn't worry about .002" on an end gap, personally.
I think using 1st over on a std bore is acceptable also, but it takes a little more breakin time.

[trbig]

Since you'll have an initial break in when you put it back together, this will make your slightly out of spec stock ones even further out. They will work if it's just all you have, but you'll get better compression using the other ones and filing them down. I would only do that to the first two compression rings though. I'd just clean up and re-use the oil ring. This one would be really tricky to get right, and there's actually three rings in that one between the top, bottom and wavy rings. A stock one cleaned up should still wipe the cylinders fine and has nothing to do with your compression numbers. Get this one just a little wrong and you score the cylinder and/or burn lots of oil.


Tod

[Crazcnuk]

Well, using 1st (or 2nd, 3rd) overrings on std pistons goes against my mechanic training, such as it is, but I have heard of other people doing it.

As I mentioned, I have 2 sets of 1st over and 1 set of std. I just need to find 2 more sets of 1st over, or 3 sets of std. To me the extra .002 is no biggie, either. The specs in the manual are the max the factory will let out. The max service limit is really where the bike becomes an oil burner or has no compression.

I am not sure if the oil rings on the bike are correct. I can't see .084 clearance on stock rings, unless the motor had 150,000miles on it. None of the rest of the block shows this much wear. In fact, the cylinders on this one are better than the ones off the bike originally, and it only had 38,000kms on it.

It looks like the PO re-ringed the motor, with either the wrong rings, or they wore out really fast. He had not staggered the gaps, either.

Remember this is the bike that had the awful oil consumption and no top end power.

[DGXSER]

I don't know nearly enough to cmoonet ont he gap and such, but even I know if you do not offset the ring gaps, you will lose compression and burn plenty oil!

[Crazcnuk]

That was the problem. This motor burnt a lot of oil. With the rings over twice the maximum service limit and the gaps together on all 4 cylinders, the oil rings were trying to be the 3rd compression ring!

I just bought 4 sets of 1st over rings off of ebay for under $50. I will use these and make them fit, unless someone wants to trade 1st overs for standards.

Also I found my Supplemental Service manual and it shows the max service limit as .0394". The manual just says .016.

[tarzan]

I think the oil rings are pretty important especially if that motor was a smoker.
You may be able to use your old wavy ring and use new for the other two oil rings just file em on the ends to fit.

[3Phase]

That was the problem. This motor burnt a lot of oil. With the rings over twice the maximum service limit and the gaps together on all 4 cylinders, the oil rings were trying to be the 3rd compression ring!

I just bought 4 sets of 1st over rings off of ebay for under $50. I will use these and make them fit, unless someone wants to trade 1st overs for standards.

Also I found my Supplemental Service manual and it shows the max service limit as .0394". The manual just says .016.

Holy Moly! I've been waiting to find out what was wrong with that engine! 0.084" end gap on the oil rails and the gaps all lined up? Using oil rails as compression rings wiped out those poor little oil rails. How much of them is left? They must look like slivers.

I'm in the middle of fitting new Standard rings to my '80G and the new, Standard, rings are smaller than the original rings. Go figure. Your 0.018" end gap is probably okay for new, Standard rings if, like the ones I bought, they're a hair or two smaller than the originals.

The new rings in mine gap at about 0.013"~0.016" for the compresssion rings and 0.020"~0.022" for the oil rails. A couple of thousandths doesn't matter but if you want to get technical, measure the bore diameter to find the circumference, then work out the equivalent end gaps for new, smaller rings versus the old, original, rings and bore..

Here are the measurements of my old rings and the new rings. The old rings have 39,000 miles on them. The new rings are Yamaha 3J2-11610-00-00 (STD).

Measured Standard Size Ring Width and Thickness:

Top Ring (RN):
Old: 3.033mm/0.1194" Wide
New:3.007mm/0.1184" Wide

Old: 1.168mm/0.046" Thick
New: 1.180mm/0.0464" Thick


2nd Ring (R):
Old:3.096mm/0.1219" Wide
New: 2.974mm/0.1171" Wide

Old:1.516mm/0.597" Thick
New: 1.483mm/0.0584" Thick


Oil rails:
Used: 2.289mm/0.0901" Wide
New: 2.235mm/0.088" Wide

Old: 0.460mm/0.0181" Thick
New: 0.450mm/0.0177" Thick


Regards,

Scott

[Crazcnuk]

I didn't check the gap on the oil rails. Just the compression rings.

There are very definite wear marks in the rails from the wavy seperator, though, more than I've seen before.

The compression was low, but not a lot. With nearly 1/8" of wide open space leading right to the top oil rail the oil ring was doing much more than it is supposed to.

[Bigleo]

rings

Hi, I would agree with your mechanics instinct about putting in the first oversize rings. I would worry that the larger rings would no longer be completely round after being squeezed that much into a smaller bore. The extra .002 on the stock size, I wouldn't worry about that at all. It's about how much Wiseco recommends for an increased gap for hot street motors.
Leo

[Crazcnuk]

What I have been told, by an expert, is that the larger rings will be slightly out of round as they are for a different radius of bore. However, he said that this just means it will take a little longer to break in, then they will be fine.

So he said to file the rings to the minimum ring gap .08 and by the time they settle in the gap will be about the middle of the recomended assy range around .012.

His take on the .018 gap for using the std ones is that they will still need a break in period and the gap will be .020 or better at that time, which is already halfway to the max service limit.