Priority #1: Rings
First, we check the face contact, to insure thay are round. Next we do a face lap to produce a uniform contact patch and create a smooth and even radius on the edges to catch oil and lift the ring face off the bore (this is the secret to less wear).
Then we check for flatness, as most rings are made from flat steel ribbon. They come out in one long coil and have a slight dish. They go through a flattening process, but due to inconsistent steel properties, about 10-25% have a "memory", as shown at right.
A few strokes on a lapping plate tells the tale. On the right, the ring top shows contact on the ID and the ring bottom shows contact on the OD. This ring will not be used.
Priority #2: Ring lands
We've found that people rarely if ever, think about ring lands. Fact is, they're as important as the rings themselves. They also need to be flat, smooth and most importantly, they need to be parallel and quite often, they're not. We spend a lot of time here.
We use a process where we actually lap the ring flats to the ring lands and do this in one process that guarantees uniform contact.
On the right, the top land is untouched. The bottom land has been lapped on both surfaces. Notice the lapped area is very consistent and has 100% contact with the ring surfaces.
The Finished Product:
When all the processes are complete, we now have a piston and ring assembly that's ready to go. Is the time and effort worth it? To us, it's not only essential, but the very foundation the performance gains we have seen for years.
Again, of the 10-15% of the performance improvements we've always seen, 50% of that comes from these efforts. The other half comes from friction reduction, which is what others mostly focus on.
It's this "not-so-little edge" that's overlooked and has allowed us to create what Eli called "the fastest bikes on the planet" for over 10 years. Thank you Eli.
NEXT READ: HOW RING LANDS ARE MADE