big bores?
3.932" is the bore size for a 98" and yes, plenty of guys with 88" are going right to 98" with stock cylinders. I would not rebuild a 95" for the 3+ displacement increase but if starting from scratch, it's a no brainer and more bang for the buck.
That is true when speaking in the context of the 96" configuration. However and just to avoid confusion, the 107" that is so popular is what is referred to as an "all bore" 107" which is a 4.125" bore on the shorter 4" stroke of the 88" configuration.
Not trying to start some chit but since the OP was based on an 88" configuration, I thought it appropriate to point that out. It can be confusing.
That is true when speaking in the context of the 96" configuration. However and just to avoid confusion, the 107" that is so popular is what is referred to as an "all bore" 107" which is a 4.125" bore on the shorter 4" stroke of the 88" configuration.
Not trying to start some chit but since the OP was based on an 88" configuration, I thought it appropriate to point that out. It can be confusing.
The 98" is all bore. Put a 4 3/8" stroker crank in it and it would be a 107". This is all based on the 88" platform bike.
Road Warrior
Joined: Sep 2010
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From: Back woods of Maine
Just a question that i"ve never heard answered in this forum. How thick are the cylinder walls before and after you bore an 88" to 98"? Seems to me that at some point, you will significantly weaken the cylinder walls. Although. I don't know where that point is.
HDF Community Team
Joined: Jun 2006
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From: san antonio
While you can get to 107" with a 3.932" x 4.375 configuration, no one does for a variety of reasons. If one was splitting 88" cases to install a 4.375" crank, I doubt that they would install 88" cylinders bored to 3.932". They would most likely case bore to fit 4.125" aftermarket cylinders for a 117" configuration.
Not splitting hairs, just keeping terminology straight.
The 98" is not all bore. All bore, or over square, refers to a configuration where the cylinder bore is equal to or greater than the stroke. An 88" reconfigured to a 4.125" bore x 4.0' stroke is an all bore 107". As you point out, an 88" reconfigured to a 3.932" bore x 4.375" stroke also displaces 107" but since the bore is less than the stroke, it is an under square 107".
While you can get to 107" with a 3.932" x 4.375 configuration, no one does for a variety of reasons. If one was splitting 88" cases to install a 4.375" crank, I doubt that they would install 88" cylinders bored to 3.932". They would most likely case bore to fit 4.125" aftermarket cylinders for a 117" configuration.
Not splitting hairs, just keeping terminology straight.
While you can get to 107" with a 3.932" x 4.375 configuration, no one does for a variety of reasons. If one was splitting 88" cases to install a 4.375" crank, I doubt that they would install 88" cylinders bored to 3.932". They would most likely case bore to fit 4.125" aftermarket cylinders for a 117" configuration.
Not splitting hairs, just keeping terminology straight.
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