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Sportster 90c.i. big bore

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Kirtap4

New Member
Hi guys. I'm considering installing a 90c.i. big bore kit on my 2003 Sportster XLH. I've done engine work on my previous Dyna but new Sportsters. I could use some help on figuring out which cams, stock carb or upgrade, ignition and any other shop tricks out there. Can I use the stock heads with mods or go with new performance ones? I've read the threads in the past and you guys are great. I just joined and looking forward to being a part of HDTALKING. Any help would be great. Thanks Kirtap4
 
Welcome to the forum. By increasing to 90 cu. in. you are making a bigger hole to drop money into.:D There is the old saying "As long as I'm in here .....". Figure out what you want out of the bike, and the type of riding you will be doing, then put together a package that all of the parts work together. Having no idea what you want out of the bike, I won't try and recommend parts.
 
I am thinking that trading the Sporty along with the money you will spend for the BB kit and all the peripherals for a later model dyna or softail with a 96" motor and six speed tranny would be the smarter move.:D But that's JMHO.
 
Yeah, maybe I'm thinking too crazy. What I have is the 883 Xl and I'm looking to make a hot street bike. While the 883 surprised me with the power it had, I know it's a good platform to build on. Ok, say I go with a 883 to 1200 kit and stock heads, I'm trying to get a handle on what else it needs to make it really pop. I'm a disabled Vet and I don't go on the long rides anymore. I enjoy wrenching on my bikes and don't mind spending a few bucks to get it right and when I ride I want to go fast when safe. Thanks for the kick and the welcome. I have some ideas but want to hear what works.
Thanks, Kirtap4
 
As the gearing is a wee bit different in the 883 when a 1200 kit is fitted the upgraded bike will accelerate quicker than a stock 1200 but will not achieve the same top speed and will be at higher revs at a steady speed

Brian
 
3 13/16" stroke(stock)combined with a 3 13/16" bore will yeild 88".
With a set of Andrews #6 cams and headwork, easy to see 100/100 with a good pipe and good induction system.
Cases need to bored, and crank re-balanced for the heavier piston gram weights.
On the flip side of that, a 1200cc XL is in fact no slouch either, set up correctly.:)
 
I've seen a few folks upgrade with a 1250 kit that will wake things up a little more than HD's 1200 conversion.
 
Have to remember that if the tranny goes up in smoke, the whole engine has to come out; not like a TC where a tranny problem can be addressed separately. So, with that in mind, avoiding over powering the gear box as well as the brakes and suspension would be a good idea.

The MoCo upgrade from 883 to 1200 with a good velocity port job, say from BigBoyz, would probably satisfy the OP's requirements. IMHO, the cost/benefit relationship, i.e., $$/HP diminshes once you increase displacement beyond 1200cc. Cost increases exponentially but not the TQ/HP. JMHO
 
Adding to my previous to clarify. I was referring to the top end conversion in my previous post; 883 to 1200. A set of Andrews N2 cams and a velocity or "stree" port job from BigBoyz or the porter of choice to complete the package.

Also forgot to mention fuel management if the bike is EFI. Talk to local tuner(s) to find out their system of choice and go with it. Of course, if carbed a rejet is required. Might also want to consider an programmable ignition like the DTT unit.

Not a Sportster guy but exhaust is important; do some research, look at dyno sheets to try and find out what works best.
 
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