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Fresh rings and hone?
- Thread starter timtune
- Start date
You're gonna need to hone it if you want the rings to seal.
Piston rings are supposed to be elastic. 48 year old rings haven't been elastic for more than a few decades.
I recommend Total Seal rings. They are definitively the best rings readily available.
...you're going to need a micrometer to measure the ring thicknesses. You can buy a set of rings for the price of a CHEAP micrometer.
You DO want to re-ring the thing.
Piston rings are supposed to be elastic. 48 year old rings haven't been elastic for more than a few decades.
I recommend Total Seal rings. They are definitively the best rings readily available.
...you're going to need a micrometer to measure the ring thicknesses. You can buy a set of rings for the price of a CHEAP micrometer.
You DO want to re-ring the thing.
It is possible to DIY with the right tools provided that you are not starting from a situation with excessive wear. I have a cylinder de-glazing tool, the spring-loaded-three-arm type as opposed to the bottle-brush type. There is a knack to doing it and getting the right cross-hatch angle, and it took me a couple of attempts that didn't work before achieving something that did. You need a drill motor that has good controllability at a really low speed so that you can get the crosshatch angle in the ballpark.
Measuring piston ring end-gaps at different points in the cylinder can tell you something about cylinder-wall wear. Near the bottom of the cylinder below the normal travel path of the rings should have minimal wear. The highest-wear area should be a few millimetres below the uppermost position of the bottom ring. If there is little or no difference in the end gap, there's not much cylinder-wall wear. Also, if the old cross-hatch was visible, there's not much cylinder-wall wear (although you'll still have to refresh it). Look on the thrust side of the cylinder wall (rear, on a normal bike engine) about 10 - 15mm below the top of the cylinder and see how much cross-hatch is left there. That's where it usually wears out first. Divide the difference in end-gap by 3(.14159... if you are pedantic) and you get the difference in cylinder diameter between your measurement locations. Compare that to specs. Do make sure the piston ring is square to the bore when doing so. The piston is usually a good tool for doing that.
A de-glazing tool takes a loooong time to remove a significant amount of material. Still, don't overdo it. Once you have cross-hatch evenly covering up any minor scuffing and the above-mentioned smooth spot, you are done. Minor vertical scuff-marks (that you can't feel with a fingernail) don't have to be completely taken out. The cross-hatch should be visibly more prominent than what's left of the vertical scuff-marks. That's when I stop. I'm quite sure that someone else will tell me I'm doing it all wrong. That seems to be the nature of this chore.
If your buddy has successfully built engines that didn't turn out to be oil burners, let him do it. You are dealing with an iron-liner engine. They're easier.
Measuring piston ring end-gaps at different points in the cylinder can tell you something about cylinder-wall wear. Near the bottom of the cylinder below the normal travel path of the rings should have minimal wear. The highest-wear area should be a few millimetres below the uppermost position of the bottom ring. If there is little or no difference in the end gap, there's not much cylinder-wall wear. Also, if the old cross-hatch was visible, there's not much cylinder-wall wear (although you'll still have to refresh it). Look on the thrust side of the cylinder wall (rear, on a normal bike engine) about 10 - 15mm below the top of the cylinder and see how much cross-hatch is left there. That's where it usually wears out first. Divide the difference in end-gap by 3(.14159... if you are pedantic) and you get the difference in cylinder diameter between your measurement locations. Compare that to specs. Do make sure the piston ring is square to the bore when doing so. The piston is usually a good tool for doing that.
A de-glazing tool takes a loooong time to remove a significant amount of material. Still, don't overdo it. Once you have cross-hatch evenly covering up any minor scuffing and the above-mentioned smooth spot, you are done. Minor vertical scuff-marks (that you can't feel with a fingernail) don't have to be completely taken out. The cross-hatch should be visibly more prominent than what's left of the vertical scuff-marks. That's when I stop. I'm quite sure that someone else will tell me I'm doing it all wrong. That seems to be the nature of this chore.
If your buddy has successfully built engines that didn't turn out to be oil burners, let him do it. You are dealing with an iron-liner engine. They're easier.
Mad Mike
Well-known member
If you have it apart, I'd hone and ring -- then you're good for another 50,000km or more. Imagine how bummed you'd be if she lost a little compression or started quiffing blue after you invested all that time into the motor?
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