If I buy O.S. Factory cylinders to make a 95”or 103” engine will my cylinders be thicker?

If you’re thinking of doing an 88”to 95” or 96” to 103” you actually will have the same size bore.

• (Stock 88” 3.750 Bore 4.000 Stroke) bore to 3.850 to get 95”
• (Stock 96” 3.750 Bore 4.375 Stroke) bore to 3.850 to get 103”

Your cylinders need to be approximately 0.100 bigger to get the added inches. No matter what decision you make, the cylinders are the same thickness.  The outside of the cylinder that goes down in the case is the same size. If the cylinders were thicker you would have to bore your cases out bigger.

Should I buy new cylinders?

Factory OEM big bore kits are mass produced.  Typically, we have found them to have too much piston to wall clearance.  Here are some of the problems this can cause:

• Blow By
• Unnecessary Horsepower Loss
• Excessive Crank Case Pressure

Boring your cylinders

No, there are many ways to bore a cylinder.  Just because you have state of the art equipment does not mean you will have the best results.
Generally, most boring bars center over the cylinder and follow the existing hole boring it out bigger.  Sounds good, right? It is most of the time, but Harley Davidson cylinders are cast aluminum with a cast iron sleeve.  The sleeve is rarely straight with the gasket surface. If you blueprint* your engine when assembling you will most likely find your deck height to be off from front to back and side to side.