100 Inch Engine Build

[Buddy WMC]

Hi Guys,

Although I am very satisfied with the performance of my 85" engine, I enjoy doing my own work. Planning now to get the parts together to build a spare engine over the next year. I have an S&S 4 1/4" set of flywheels and rods and prefer the short stroke/big bore combo over a stroker motor. I also have access to a set of Revolution Performance 3.875 bore cylinders and pistons that would be compatible with the ported SE heads that I already use on the 85" engine.

The recommended cam for this setup is a Woods 8, my current V-Thunder EVL-5015 only has one degree difference in it's timing from the Woods 8 and should work just fine. From what I have been able to find out the 3.875" and 4" aftermarket cases available are all made on a 4" S&S stud pattern. Going that route would require too many changes and additional parts costs. Ultima used to offer a 3.875 bore case and still offers a 100" engine, but for some reason the cases themselves are no longer available. Boring my present 93 cases are too risky, so the question becomes this.

Are there any options anyone knows other than to purchase a set of 3 5/8" cases and have them bored to 3.875? I'd appreciate any input before I leave for Daytona on the 5th. While there I'll try and scrounge up some parts.

[Hillside Motorcycle]

There are no cases manufactured to accept the 3.875" bore cylinder spigots.
Boring the cases is a piece of cake.
Scott

[stroker800]

  Have considered building a "fatvo or fatso " motor to get to your 100"..I have also seen ultima cases on ebay, as I was thinking of yusing my xtra TC cyls and heads on a custom build of sorts.
Dave

[Buddy WMC]

Stroker,
Thought about it, but do not want any interference or major fabrication problems with an FXR frame. Just looking to build the larger engine, put her in and go.

Hillside,
Do not wish to bore my current 92 cases. With swapping the SE heads back I'd have a complete spare engine. With another set of heads installed I'd have and engine to sell with less than 2K if I chose to do so.

What about the Ultima 3 5/8 bore case idea and bore them out to 3.875?

[dave_9113]

Buddy,

You have too much time and $$.    Hope you are doing well.  Nothing new to report here.

dave

[Buddy WMC]

Hi Dave,
Time yeah, money is tight like everywhere. I plan to collect the parts needed over the next year or so. Finally off the treatments after 17 months and starting recovery. Want to get this done before I'm too old to enjoy it

[Bullwinkle]

>>Thought about it, but do not want any interference or major fabrication problems with an FXR frame.<<

I can't see why you would have any interference problems.  I have a 1993 FXR and over the years besides stock I've had an 88" (3 5/8 X 4 1/4) and right now have a 4 1/8 bore 111".  No problems with either.  Nothing whatsoever, except making sure the intake manifold is the correct length (width?) if you lap the cylinders and mill the heads.

It isn't so much the cylinder diameter as it is where the cylinder head, and more correctly, the rocker box, is, and that is a function of the deck height of the cases and the length of the cylinders.  Even the 4 1/2 stroke of the S&S 113 fits fine.  I'm sure the 124 will fit in an FXR, too.

Depending on your valve lift and type of rocker arms, there might be smaller rocker boxes that will help clearance.  I have a 120 in another scoot and it has Sportster rocker boxes.  They are slightly scalloped in on the front and rear and might help with clearance.

Take a good look from the side at where things fit.  You should be OK.

Bullwinkle

[Buddy WMC]

Bullwinkle,

Hey bud, I was not concerned about an EVO based engine. The Fatvo however utilizes a TC top end that we all know is larger, not sure about the rocker box clearances etc. I do not want to commit to going that way without knowing for sure.
I was advised by Revolution Performance (we are dealers), that both the stock and 3 5/8" Ultima cases have enough meat in them to go out to 3.875 and if that is true then I'm all set. I have a call into Ultima technical now to confirm this.

If so, I'll order the cases through Revolution and ship my S&S flywheels up to them. They will bore the cases, balance the flywheels for the 3.875 pistons and assemble the short block at a very fair price. I'll take it from there when we are ready to swap the engine out.

[baldoldfxr]

there was a twincam engined FXR on the show your fxr thread.