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[Dan_Lockwood]

I've seen over the years a chart here or there of what the stock bore/stroke is of different Twin-Cam motors.  I've done several searches and nary a one to show up...

What I have is a new to me 103" "B" CVO Fat Boy motor and was wondering what low cost options I may have in upping the displacement a bit.



I'm not really looking for hp as this will be in a very light car, I'm looking more to the torque side rather than hp side.

Because it will be a standalone install with hot rod type wiring harness, I will be using a Thunderheart standalone ignition system and a new Ultima R2 carb that is a S&S Super E clone.  I want to stay a bit smaller on the carb rather than the R1 (or Super G) as a smaller throat usually has a bit more throttle response and sometimes helps the low to mid range drivability a bit.  The car will weigh in around 1250# dry and will be running a Miata 5 speed with either a 3.9 or 4.3 rear differential with 19" wheels with 28" tall tires (4.00x19").  I'm hoping the gearing will net me around 65 mph @ 3200 rpms.  So developing hp are lower rpms will be beneficial to my use, not 1/4 mile time slips...

Originally I was looking at an '02 88" "B" motor with the left side Timken bearing, but this '05 103" popped up at a GREAT price and it was already larger than I could upgrade an 88" to at a reasonable price point.  I don't know if I need or want more displacement, but would like to know what options are out there if I want a bit more oomph… 

Simple question, will 110" cylinders fit onto the 103" case without boring the cases?  If so, what if any head mods would need to be done?  Is the stroke the same as a 110", but just a smaller bore?  Again torque is my goal in the 2500 to 4000 rpm range.  I guess that's really not different than most people want on their bikes, but hp is usually the driving force for bike upgrades, not torque per se. 

You see where I'm going with my thinking.  Or maybe I'm not thinking... 

Thanks in advance and have a great day!

[Twolanerider]

Without splitting the cases?  With just top end work you're about done.  1/16" bigger and go to 107"

[Dan_Lockwood]

Without splitting the cases?  With just top end work you're about done.  1/16" bigger and go to 107"

Thanks Don.

So the spigots on the 110" are larger than the case is bored for the 103" I take it.

Still would like to see what all the bore/strokes are of the different Twin-Cam motors.

Are there different versions of the 103" motor?  Are the early 103" CVO motors the same bore/stroke as the later non CVO motors?

[hd-dude]

There are 110" drop-on barrels from S&S and the MOCO available. If you are trying to keep a tight budget then boring your barrels to 107" is a better choice.

[Dan_Lockwood]

If I go the full tear down route to get a good paint / powder coat job on the motor, I know I'll at least re-ring it and have a valve job done just for safety sake.  "IF" it's had a gear drive installed like the guy I purchased from said it has, don't know what I'll do; new lifters, new chain drive cams etc?

Even without the complete tear down to get repainted etc, I will be taking the cam chest cover back off, doing an inspection and re-gasket the cover at a minimum.

Thanks!

[Dan_Lockwood]

I found this on the V-Twin forum.



I'm assuming some are stock Harley and some are over bore and over stroke options.

So my 103" is 3.875"/4.375", correct?  Are ALL Harley factory 103" motors the same bore/stroke?

A .0625" over bore (3.938") will net me the 107" that has been mentioned above.  The S&S special 110" cylinder/piston set have different liners I take it that can be bored to 4.0" and still have the spigot strength needed without having to bore the cases larger for the Harley 110" cylinders.

Although if this is the case with the 110" Harley cylinders just needing the cases bored, "IF" I do tear down the motor for a recolor, it may be cheaper to just pick up a used set of 110" cylinders, new rings and then just have the cases bored prior to the new color job.  I've seen 110" cylinder sets on our for sale page very cheap after popping up to the 117" kits.

Just a thought.

Thanks again all... 

[Twolanerider]

Dan, just saw this again.  The early and late 103s are not the same engine.  The latter engine is just a larger bore of the 96" engine. 

The earlier 103" was the fat grandchild of the 88".  88" got a larger bore to go 95".  The 95" displacement is stroked to get to 103".

88" 3.75 x 4.00
95" is more bore to 3.875" x 4.00 stroke
103 keeps the 3.875 but lengthens stroke to 4.75.

The aftermarket 107" options add a 1/16 to the bore to end up 3.9375.

The 110" kit that Dude mentioned (that I'd forgotten all about) is still all bore.


So all the Twin Cams that are derivative of the original 96" geometry don't play on your version of the 103".  The only thing you can do without splitting cases is the pretty common 107" or the 110" option that is, so far as I know, only done by S&S.

[98fxstc]

110 drop ins are done by S&S and HD

Check with Don (HD Performance) about this process
He seasons his cylinders and hones for 0.010"os for true cylinders with pistons appropriate to compression required

[prodrag1320]

I found this on the V-Twin forum.



I'm assuming some are stock Harley and some are over bore and over stroke options.

So my 103" is 3.875"/4.375", correct?  Are ALL Harley factory 103" motors the same bore/stroke?

A .0625" over bore (3.938") will net me the 107" that has been mentioned above.  The S&S special 110" cylinder/piston set have different liners I take it that can be bored to 4.0" and still have the spigot strength needed without having to bore the cases larger for the Harley 110" cylinders.

Although if this is the case with the 110" Harley cylinders just needing the cases bored, "IF" I do tear down the motor for a recolor, it may be cheaper to just pick up a used set of 110" cylinders, new rings and then just have the cases bored prior to the new color job.  I've seen 110" cylinder sets on our for sale page very cheap after popping up to the 117" kits.

Just a thought.

Thanks again all... 

most common used 124 build is 4.625 x 4.125

[Dan_Lockwood]

One last, I hope, question...

If I had a set of CVO 110" cylinders/pistons, they would be usable in my 103" "B" motor with the cases bored out to fit the larger spigots, correct?

Okay, two questions.

When the cases are bored out for the larger cylinders, is there any harm of the cylinder studs not having enough grip in the cases to retain the motor together?

Thanks and keep that damn virus at bay!

[johnsachs]

One last, I hope, question...

If I had a set of CVO 110" cylinders/pistons, they would be usable in my 103" "B" motor with the cases bored out to fit the larger spigots, correct?

Okay, two questions.

When the cases are bored out for the larger cylinders, is there any harm of the cylinder studs not having enough grip in the cases to retain the motor together?

Thanks and keep that damn virus at bay!

Question #1 - correct
Question # 2 -No issues no harm
John

[Dan_Lockwood]

Question #1 - correct
Question # 2 -No issues no harm
John

John, thanks!

[DCFIREMANN]

I took my 2004 103 SEEG to 113. All I did was get a set of pistons and had the cylinders bored. It has 30K on it and still runs like a champ.

Be Safe

THE DAWG

[johnsachs]

John, thanks!

Originally a 2000 Softail. This was a 110" (bore the "B" case ) conversion I did a few months ago. I found 2 NIB 110" SE kits #(29912-07) at Daytona Harley swap meet, for a good price. Had to buy them. 
John

[Dan_Lockwood]

John,

Nice looking motor.

Do you repaint motors like the black one when you do a rebuild like this?  If so, what wrinkle black paint do you use?

Thanks!