Choosing Radical or Refined

Do you want to have the most power for the drag strip or perhaps racing from stoplight to stoplight? Or would you rather have the most power for rolling on the throttle to pass a truck while cruising? You can’t exactly have both.

The basic, engine power equation works like this: To get the highest possible peak-horse-power (dyno) numbers, your component selection will limit your increase in low-and-midrange RPM (normal riding) power.

To get the greatest possible normal riding power, your component selection will limit your increase in peak RPM power and the associated horse power (dyno) numbers.

Properly built, most any big-bore engine will produce noticeable horse power and torque increases in all RPM ranges. So, it's just a matter of deciding what kind of bike rideability you want, and how much money and time you're willing to spend to get it.

I wanted to develop the most cruising roll-on power (torque) possible, even though I would have to settle for a little smaller increase in peak horsepower. This meant that I would not want to use ported heads, oversized valves, or high-lift cams.

After a thorough discussion with my suppliers, I felt that my selections would yield the most rideable, commute-able, and powerful bike for my money and time. Also, I could add the other components later, without another complete tear down, if I wanted.

How big an engine do you want: 108ci?, 110ci?, 113ci?, 122ci? And what are you willing to do to get it?

Going from stock to 108ci or 110ci is fairly straightforward:

• Disassemble the top end of the engine--down to the cylinders.
• Send your cylinders to the supplier or a machinist, depending on which manufacturer you choose.
• Wait for them to machine your cylinders to spec.
• Receive the modified cylinders, new pistons, new rings, gaskets, and other performance parts for you to install.
• Build the engine back up, and adjust your engine to allow for the added power (i.e. carburetion and/or exhaust changes).
• Button everything back up.

Skip Dowling of Orient Express feels that there no inherent performance gains between 108ci and 110ci. It is strictly a matter of bragging rights (actually, Skip’s words were a little more delicately phrased). And all the experts I spoke with agreed that going beyond 113ci created no more horsepower, and stretched the outer limits of the Road Star’s dimensions.

With pistons larger than the 108 - 110ci arena, it is no longer possible to simply take out the pistons and cylinders, increase their size, and put everything back together. This is because the cylinder sleeve diameter exceeds the size of the hole in the crankcases. Then it becomes necessary to remove the engine and transfer case, remove the clutch, generator, cams, crank, transmission and oil pump assemblies, take the crankcases apart (called 'splitting' the cases), send the cases to a machinist, have them bored, clean everything spotless, and then reassemble all the above.

Sadly, Nemesis Racing no longer offers the 113ci kit, which I purchased. This definitely demanded total engine disassembly. It's a lot of extra work, but I elected to do this because I really enjoy tinkering, I wanted to learn every bolt in my bike, and I had the time.

Want to go all the way to 122ci? In the words of Nigel Patrick of Patrick Racing, "If you have to ask how much it costs, we'd rather not do it. The price varies from engine to engine."

Orient Express has a fixed price for their 122ci. However, Skip Dowling, owner, recommends their 122ci engines be used as ‘bar hoppers’ or ‘show bikes’, not daily or long-distance use. All suppliers feel that boring the cylinders beyond 113ci leaves precious little cylinder wall material left.