First, both new and re-plated cylinders must be cleaned prior to assembling. Normally the cylinders will arrive looking clean, but looks can be deceiving. I have no doubt that the factories and re-plating services clean the cylinders as part of their processes, but I highly recommend cleaning the bores a final time prior to use. Shown below is a new Yamaha cylinder that I extracted quite a bit of honing grit out of.
What’s the best way to clean the cylinder bore?
Start by using warm soapy water and a brush to clean the cylinder. Take your time and be thorough.
As a test to check cleanliness, rub a cotton swab against the cylinder bore. If the swab picks up any debris and changes color, your cleaning duties are not over. The swab should be able to be rubbed against the bore and remain perfectly clean.
Two-Stroke Port Dressing
For two-stroke owners, the second item I want to bring to your attention is port dressing. Port dressing is a term used to describe the process of deburring/breaking the edge at the intersection of the cylinder plating and the ports in the cylinder. During the plating process, plating usually builds up excessively at the edge of the port and must be removed after honing. Proper removal is critical to ensure acceptable piston ring life.
Two-Stroke Power Valves
Lastly, it is possible that some of the power valve components, such as blades or drums, will not fit correctly on cylinders that have been replated. This is because the plating can occasionally build up in the slots or bores where the power valve parts reside. Prior to final assembly, be sure to check the function of the power valve blade and/or drums to ensure they move freely in their respective locations within the cylinder.
If plating has built up in a power valve slot or bore, it will need to be carefully removed. To do this, appropriately sized burs for die grinders or Dremel tools can be used. If one is not careful, irreversible damage to the slot or bore can result. When performing this work proceed cautiously or leave it to a seasoned professional. Burs for the job can be difficult to track down in stores, but are readily available online from places like McMaster-Carr. When purchasing burs, be sure to pick up a few variants, such as rounded and square edged, designed for removing hard materials.
The Two-Stroke Book
From February to March we photographed the entire book. From April onward we have been formatting and proofreading. Needless to say, we are in the final stretch! If you want to stay updated on the moment the Two-Stroke Dirt Bike Engine Building Handbook is ready for pre-order, sign up at the link below. We can't wait to get this book out the door and into your garage.
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Thanks for reading and have a great rest of your week!