Part: "Pulsar" Series Oversize Piston Kit for Honda CB350 K1-K5 + G / CL350 Scrambler K1-K5 / SL350 K0-K2 Motorcycles - TWO PISTONS ARE IN THE KIT
Why You Need This: After many years and countless miles of faithful service your vintage Honda CB350 / CL350 Scrambler / SL350 will inevitably need a top end engine overhaul. During the engine rebuild process the cylinders on your Honda need to be measured to see if they are within published service limits. If things measure out fine and there is plenty of material left in the cylinders and hone and re-ring may be all you need. However if you find the cylinders are over service limit (or are very close to being there), then the cylinders will need to be bored oversize. This will require new matching oversize pistons and piston rings along with a new wrist pin and retaining clips in order to correctly finish your rebuild.
Original Honda oversize pistons and matching rings are obsolete for the CB350 / CL350 / SL350 family of motorcycles; while our performance forged pistons are a nice piece of machine work and ready for racing, they are expensive for most of daily drivers.
As usual, CMC steps in to make the parts that we all need to keep our vintage Honda CB350 / CL350 / SL350's on the road. We are happy to introduce the "Pulsar" series oversize pistons. The "Pulsar" series pistons are based on the original ART cast aluminum pistons that came new from Honda. However, with the advances in modern manufacturing processes, we have added a number of performance improvements to the original designs.
- Each "Pulsar" piston is made from pressure cast aluminum and CNC finished machined.
- Piston skirts feature a MoS2 (molybdenum disulfide) dry film lubricant anti-friction coating to applied to the aluminum surface to reduce wear and scuffing.
- Piston crown and the top ring groove have a high temperature hard anodizaton applied to the surfaces to increase overall piston durability and thermal transfer (important in an air cooled engine) as well as preventing the top ring from micro welding (aka getting "stuck") into the ring groove.
Speaking of rings, the "Pulsar" series pistons include modern piston rings to improve sealing, ease of install and ensure long service life. Each ring set includes:
- A gas nitride coated forged steel top ring (silver). This is a hard coating on all surfaces of the ring and gives increased wear resistance and lower coefficient of friction on the cylinder walls.
- Steel phosphate coated 2nd ring (black).
- Modern gas nitirde three piece oil ring, which makes installation on to the piston and cylinder assembly as LOT easier that old style cast iron one piece oil rings.
Additionally the "Pulsar" series pistons kits also include new writs pins (gudgeon pin) and the proper "C" style retaining clips, for correct fit with minimal pin slop.
"Pulsar" series Pistons are available in the the following oversize options:
- 0.5 mm Oversize - #4302
- 1.0 mm Oversize - #4303
This "Pulsar" Series piston kit contain TWO PISTONS, one kit will rebuild one engine
Complete the rebuild properly with an overhaul gasket kit, cam chain , oil seals and a new cam chain tensioner kit.
Installation Tip: Install piston rings with the marked side facing up toward the crown. On the 3 piece oil rings, the wavy ring goes on first and then is sandwiched by the thin rails on the top and bottom. The "C" style wrist pin clip is installed with the open end opposite from the notch in the side of the piston. Ensure that the clip seats fully in the circumference of the groove as sometimes the end of the clip can catch and not fully engage. Put the clips on the inner side of each piston (side closest to the cam chain) before placing the pistons on the connecting rods. Thus install the wrist pin from the side of each piston facing away from the cam chain. Put some rags in the engine case and cam chain hole so you do not drop the wrist pin clip in the bottom of the engine case! Check small end of the connecting rod inner diameter for wear beyond service limit. Install the pistons with the arrow facing toward the front of the engine. Make sure to lubricate the pistons and cylinders with motor oil before installation.
Cylinders must be bored oversize by an engine machine shop, and it is best to have the new pistons available to the machinist when dropping the cylinders off for work. We recommend a 0.0015" to 0.002" piston to cylinder wall clearance when over boring cylinders. Wash newly machined cylinders with hot water and dish detergent. Wipe the cylinders clean with a white cloth, when the cloth shows no dark residue the cylinders are ready for reassembly.
