Piston Rings | Honda CB350 / CL350 / SL350
When a CB350 starts smoking, burning oil, or losing compression, worn piston rings are usually the reason. This modern ring set re-seals the bore and gets the engine back to spec — available in standard and two oversizes, so it works whether you're doing a simple re-ring or a full overbore rebuild.
Why You Need This
The CB350 twin is a tough engine — plenty of them are still running strong with big miles — but rings wear, and when they do you get lost compression, blow-by, and burned oil. Many CB350 engines don't need an overbore: if the cylinders still measure within the factory service limits, a light hone and a fresh set of standard rings brings them back. If the bores are worn past the limit or scored, they'll need boring oversize, which calls for oversize pistons and matching oversize rings. This set covers both paths.
Which Size Do I Need?
Measure your cylinder bores, or match your pistons, and select the size above:
- Standard — for a 64 mm standard bore that's still within service limits (a light hone and re-ring).
- 0.5 mm Oversize — for cylinders bored 0.5 mm over, running 0.5 mm oversize pistons.
- 1.0 mm Oversize — for cylinders bored 1.0 mm over, running 1.0 mm oversize pistons.
Oversize rings fit factory Honda oversize pistons and our “Pulsar” oversize piston kit.
Specifications
| Spec | Detail |
|---|
| Fits Models | Honda CB350 / CL350 / SL350, K0–K5 (1968–1973) |
| Available Sizes | Standard (64 mm bore) / 0.5 mm oversize / 1.0 mm oversize |
| Replaces OEM | 13011-287-010, 13011-391-004, 13031-287-010, 13031-391-004, 13051-287-010, 13051-391-004 |
| Sold As | Sold individually — one ring set per piston (two sets for a twin engine) |
What's in Each Ring Set
- A gas-nitride-coated forged steel top ring (silver) — hard-wearing, with a low-friction face on the cylinder wall.
- A steel-phosphate second ring (black).
- A modern three-piece oil ring — far easier to install than the old brittle one-piece cast-iron oil ring.
Installation
Difficulty: Advanced — done as part of a top-end rebuild.
- Check the ring end gap in the bore before installing. A fresh compression ring should measure 0.008–0.016" (0.2–0.4 mm); a gap at or past the 0.032" (0.8 mm) service limit means the bore is worn and standard rings won't seal it.
- Assemble the three-piece oil ring in its groove — the wavy spacer first, then the thin rails above and below it.
- Fit the top and second rings with any markings facing up toward the piston crown. The CB350 replacement rings are symmetrical, so an unmarked ring with the same profile top and bottom can go either way.
- Stagger the gaps so none line up: set the top and second ring gaps 180° apart, and the three oil-ring openings 120° apart.
- Oil the rings and cylinders before assembly, and re-check that the gaps haven't rotated back into line right before you slide the cylinder down.
You can watch the whole job — setting the ring gaps, assembling the oil ring, and getting the cylinder back on — in our CB350 / CL350 top-end rebuild video:
Frequently Asked Questions
How many ring sets do I need?
Rings are sold individually, one set per piston — so a twin needs two sets. Order two for a complete CB350 / CL350 / SL350 engine.
How do I know which size to order?
Measure your cylinder bores, or match your pistons. A standard 64 mm bore within the factory service limits takes standard rings; if the cylinders have already been bored oversize, order the size that matches your pistons (0.5 mm or 1.0 mm).
Standard or oversize — how do I decide?
It comes down to whether your cylinders are within the service limits. If they measure good, a light hone and standard rings will re-seal them. If they're worn past the limit or scored, they'll need boring oversize, which means oversize pistons and matching oversize rings. When in doubt, have the bores measured before ordering.
Do the oversize piston kits already include rings?
Yes — our “Pulsar” oversize piston kit comes with matching oversize rings, plus pins and clips. This ring set is for when you need rings on their own — a re-ring on standard pistons, or replacing a set on pistons you already have.
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Last updated: July 2026
