Educate me on Big Bore Kits
Thread Starter
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Tourer
Joined: Apr 2007
Posts: 438
Likes: 57
Educate me on Big Bore Kits
I have a mostly stock 2008 Street Bob - the only mod is a SE exhaust. Down the road I want to put in a 2 into 1 exhaust along w/ a cam and tune. Want to really increase low to mid torque and not go for max Hp. Seems like going to a 103 SE kit would only add $500 or so. Would it make sense to do so? I would do the labor, so I am guessing that the the 103 kit, exhaust & tuner would be $2500 or so.
Is 103 as large as you can go with a simple cylinder & piston swap? Are there kits other than SE that I should consider? What about tuners (I don't know much about them) - which one should I consider?
Not planning on doing this just yet (need to spend $$$ on brake & suspension first), but do want to get my ducks in a row for when I get around to the engine work..
Is 103 as large as you can go with a simple cylinder & piston swap? Are there kits other than SE that I should consider? What about tuners (I don't know much about them) - which one should I consider?
Not planning on doing this just yet (need to spend $$$ on brake & suspension first), but do want to get my ducks in a row for when I get around to the engine work..
Seasoned HDF Member
Joined: Mar 2012
Posts: 100,455
Likes: 19,811
From: Centennial, CO
107 is about as big as you can go.
Scott at Hillside is the man to talk to about a kit that willl be put togther as a system. Better than anything HD can provide.
Power Vision from Fuel Moto for a tuner and a dyno tune from your local Indy.
Scott at Hillside is the man to talk to about a kit that willl be put togther as a system. Better than anything HD can provide.
Power Vision from Fuel Moto for a tuner and a dyno tune from your local Indy.
Banned
Joined: May 2018
Posts: 4,576
Likes: 978
From: Viet Vet, crossroads
You have to think of cams exhaust and fuel as a symphony that works well together.
With big bore kits, some require stroker kits to achieve said displacement.
Then there is the argument over Sq / under Sq etc . Personally rather than relying on the novice armchair mechanics here-
I would contact a few places that really know what works with what so you are not reinventing the wheel,
Talk to Ron at Axtell, Talk to Dan at Baisley and other very reputable places that have a pedigree in this .
They know what compliments what.
Your local HD shop I am sure will sell you a SE big bore kit, but there might be better options.
With big bore kits, some require stroker kits to achieve said displacement.
Then there is the argument over Sq / under Sq etc . Personally rather than relying on the novice armchair mechanics here-
I would contact a few places that really know what works with what so you are not reinventing the wheel,
Talk to Ron at Axtell, Talk to Dan at Baisley and other very reputable places that have a pedigree in this .
They know what compliments what.
Your local HD shop I am sure will sell you a SE big bore kit, but there might be better options.
If you're going to all the work of switching cylinders, go with a 107" or 110" kit. A little more money, but a more noticeable power increase. It's not just the extra cubes, but the aftermarket (S&S, Fuel Moto, etc.) kits have more compression than the Harley stuff. Pair with the right set of cams you can make some nice power.
Elite HDF Member
Joined: Sep 2008
Posts: 4,440
Likes: 148
From: Northwest
Personally, I think there is a lot power potential left on the table with the 96. Up the compression with some nice headwork, cams that match where you ride 90% of the time, a good 2-1 exhaust, a good tune, balance and weld that bottom end... you'll make some good, reliable power. ... my opinion. 'course I am considering a 103 kit for my future build 
... lol
... lol
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Stellar HDF Member
Joined: Feb 2016
Posts: 2,066
Likes: 259
From: Northstreet, michigan
I would suggest going with a fm 107 or a 110. Me personally, I’d go for the 110. If you’re doing the Labor you’ll need to consider the cam bearing removal/install tools (cost me about 250 when I installed my 117 kit) and a crank/cam locking tool for when you get into the cam chest. I think that was about 35 bucks but don’t remember for sure. Search “my se 117 install” It’s a thread I posted of how to install a big bore. It’s on my 17 lrs and it’s a screamin eagle 117 kit, but it’ll give you a good idea of what you’re in for since it’s pretty similar to what you’ll be doing.
For a tuner, I’d highly suggest power vision. If you go with power vision, you most definitely want to buy it from fuel moto as they will send you a free tune for your specific upgrades. Then just run a few autotune sessions and you’ll be good to go.
Youll also want a good free free flowing air cleaner and a 2-1 exhaust like you mentioned previously. For exhaust, the best choices would be either the road rage or fat cat. Everytime someone posts dyno results with either of those they seem to make 5-10 tq more than those running other exhausts. I have a fat cat on mine and I couldn’t be happier. It’s a little on the louder side which is my preference but not everyone wants to be heard from 4 miles out.
For a tuner, I’d highly suggest power vision. If you go with power vision, you most definitely want to buy it from fuel moto as they will send you a free tune for your specific upgrades. Then just run a few autotune sessions and you’ll be good to go.
Youll also want a good free free flowing air cleaner and a 2-1 exhaust like you mentioned previously. For exhaust, the best choices would be either the road rage or fat cat. Everytime someone posts dyno results with either of those they seem to make 5-10 tq more than those running other exhausts. I have a fat cat on mine and I couldn’t be happier. It’s a little on the louder side which is my preference but not everyone wants to be heard from 4 miles out.
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Thread Starter
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Tourer
Joined: Apr 2007
Posts: 438
Likes: 57
Personally, I think there is a lot power potential left on the table with the 96. Up the compression with some nice headwork, cams that match where you ride 90% of the time, a good 2-1 exhaust, a good tune, balance and weld that bottom end... you'll make some good, reliable power. ... my opinion. 'course I am considering a 103 kit for my future build ... lol
... lolWhat do you mean on "weld that bottom end"? Is the bottom end not strong enough if allot of power is added?
