Big Bore Kits. Are they worth it???
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Intermediate
Joined: May 2014
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From: Kanuckistan
Big Bore Kits. Are they worth it???
Like the title says are they worth it? I'm thinking of doing that to an 03 but I have an acquaintance trying to tell me don't do it. Telling me to much torque I'll blow up lower end. To that I am calling BS. Any input from builders mechanics would be appreciated.
Outstanding HDF Member
Joined: May 2014
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From: Fort Worth, TX
Well how big are you talking about going? Taking an 88" to 98" will be fine as long as your crank is in good shape. Your off the shelf big bore kit or a kit from a place like Hillside will work great for you, all things considered....
Seasoned HDF Member
Joined: Nov 2010
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From: Oxford, Nc
Mine's big bored from the Factory at 95", produces 30% more power (both TQ and HP,) than an 88" and is at 150,000 miles currently. Upgraded cam, no head work. And while the later bottom ends are nowhere near the strength of the 99 to 02's, your '03 still has a forged crank (though it doesn't have the Timken Lefty bearing.) A big bore with cam is just fine for your application.
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From: Kanuckistan
Yes just going to take it to 97 (S&S) kit. since I'll be that far into it I'm thinking of upgrading cams while its apart. I would like to support a site sponsor but the current Canadian exchange rate would be a killer.
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From: Bedford UK
Is it worth it? What you get with a big bore kit is not just a few extra cubic inches, but more important a significant boost in compression ratio. That is what gives the most improvement. One reason for a 'big bore' is simply to replace the stock bore, which will be part worn (on all but a new engine) hence not suitable for simply putting in new higher CR pistons.
A change of cams is another opportunity for a performance boost if done at the same time, add ported heads and - bingo! Unless your bike has a high mileage the bottom end is likely to be fine. But speak to a trusted tuning shop and they will advise, based on firsthand experience! One has already been suggested above......
A change of cams is another opportunity for a performance boost if done at the same time, add ported heads and - bingo! Unless your bike has a high mileage the bottom end is likely to be fine. But speak to a trusted tuning shop and they will advise, based on firsthand experience! One has already been suggested above......
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From: Poolville
Imho
I really don't think they are but i've been wrong. I like to build motors with what I have and resort to more cubes if I'm not satisfied. With the dissection of camshafts today it easy to get a real good performance motor without going into the bottom end. How ever you have to do your home work and learn how different cams react to different opening and closing times of the valve. It really does determine where your power band is and defines the way you ride. however you need to ask your self what is it I want and what will satisfy me? Be honest. your never really gonna beat the next guy because there is always some one else. What will make you Happy?......
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