Part: "Pulsar" Series Oversize Piston Kit for Honda CB450 K0*-K7 + G / CL450 Scrambler K1-K5 Motorcycles - TWO PISTONS ARE IN THE KIT
Why You Need This: With decades and miles of faithful service, your vintage Honda CB450 / CL450 Scrambler is in need of an engine rebuild. With the rebuild process, cylinders will need to measured and determined if they are within the wear service limits. If so, a de-glaze hone with re-ring is in order and back in with the stock pistons you go. However if the cylinders end up measuring beyond the factory service limits, then the cylinders will need to be bored oversize. This requires new oversize pistons that match the oversize cylinder bore; this includes a new set of oversize piston rings, new wrist pin and retaining clips for a complete installation.
OEM Honda oversize pistons and matching rings are obsolete parts for the Honda CB450 / CL450 family of bikes. However, no cause for panic! The Common Motor Crew has stepped in to make new parts that we all need to keep our vintage Honda CB450 / CL450 on the road. We are happy to introduce the "Pulsar" series oversize pistons. The "Pulsar" series pistons are derived from the original ART cast aluminum pistons used 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 di-sulfide) 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:
- The top ring (silver) is forged steel with a gas nitride coating. This is a hard coating process that permeates all surfaces of the ring, increasing wear resistance and reducing the coefficient of friction on the cylinder walls.
- Steel phosphate coated 2nd ring (black).
- A three piece oil ring, which makes easy installation on the piston and into the cylinder assembly (A LOT easier than cast iron one piece oil rings). Top and bottom rails of the oil ring are also gas nitirde coated.
Additionally the "Pulsar" series pistons kits also include correct length 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 - #4306
- 1.0 mm Oversize - #4307
This "Pulsar" Series piston kit contain TWO PISTONS, one kit will rebuild one engine
Complete the rebuild properly with a gasket kit, cam chain, clutch rebuild kit and some Honda bond gasket sealer.
1) CB450 K0 (Black Bombers): originally used a different design piston with lower compression and shorter crown, These are a suitable replacement and will raise the compression to that of the K1 and up engines.
2) CB500T: with its longer stroke and shorter connecting rods, using these pistons in a CB500T rebuild will significantly lower compression due to the wrist pin hole location in relation to the piston crown. We suggest either looking for NOS 500T oversize piston, or to de-stroke your CB500T to a CB450 by replacing the crankshaft with one from a CB450 or CL450. Used crankshafts are available and the engine will run smoother.
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 0.001" to 0.0015" 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.