Ensure joint play on the piston ring
A piston ring has the task of ensuring the best possible compression. In addition, the oil control ring should also ensure that almost no oil gets into the combustion chamber. In order to optimally fulfill these tasks, the butt clearance is of crucial importance.
What you need:
- Feeling empty
Creating the correct joint clearance on the piston ring is precision work
- As long as one engine runs satisfactorily, there is no need to change the pistons and cylinders. But if you find that z. B. If steam escapes from the vent or the engine consumes oil, the cause should be investigated.
- Sometimes it is only due to seized piston rings that can continue to run after cleaning. Often, however, a replacement of the piston with all the necessary precautions is necessary.
- Once the cylinder has been ground and you have bought the new piston with rings, the real hardship begins. If only one old ring is broken, it may can be replaced with a new one without grinding the cylinder.
- New piston rings are offered in tolerance sizes, otherwise the range would be too extensive. So you need to know how big the bore of the cylinder is to get the matching piston rings.
- the test the fit is made with the aid of the piston. Slightly tighten the loose ring and insert it into the cylinder. (Caution! Risk of breakage!) This is best done with the cylinder removed.
- Now push the ring straight with the help of the plunger. Now you can see whether there is an air gap at the joint of the ring or whether the ring is completely closed. It can also be that the ends overlap.
- In the latter cases, it should be tried whether a ring from the next smaller fraction is more suitable. An air gap must be guaranteed in any case, otherwise there is a risk of serious engine damage because the ring expands in the heat.
- Check the technical documentation for your engine. There the dimension for the joint play is given in a tolerance limit. This tolerance must be adhered to in order to achieve optimal engine performance.
- If the new rings are only a few tenths of a millimeter too much, the excess material can be removed with a file or sandpaper. It must be possible to move the feeling void through the gap in a sucking manner.
- If the gap is too large, you will have to grind off a ring from the next larger fraction until it fits. It is always removed from the end of the ring that does not have a recess for the nose to prevent twisting, never from the circumference.
- If you replace a single ring with a new one, the air gap must be measured at top dead center. This is where the ring should seal best.
- Ideally, the optimal air gap is checked again when the piston with ring is installed. You can then check whether the ring can move freely in the cob groove and whether it complies with the prescribed joint clearance over the entire stroke.
- This procedure must then of course be drilled individually with each new ring. For a thorough and accurate job, you will be rewarded with a clean run and good performance of your machine.
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