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Evo Big Twins
Evolution Big Twin 1984 -1999

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  #1  
Old 26-09-2007, 10:53 PM
evo12c
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Evo performance upgrade

Hi considering big bore kit for my 1994 evo fatboy, done the usual work, air, exhaust, ignition, cam, but still need more, probably head work and pistons, any advice appreciated, was a guy on here a while ago posted a step by step of his engine build, it was a springer, I remember edlebrock heads, anyone remember or give me a clue.
anyone had there heads reworked, a good shop recomendation would be appreciated, BOZ Engineering has been mentioned.
thanks
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  #2  
Old 27-09-2007, 07:36 AM
Kiwi
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Re: Evo performance upgrade

what year is your evo? some year evo's had particulary weak cases

possibly be cheaper and easier to sell your motor and buy a 96" - 113" s&s motor

there is no replacement for displacement

a good big motor will always beat a good small motor
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  #3  
Old 27-09-2007, 08:39 AM
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Helmetbolt Helmetbolt is offline
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Re: Evo performance upgrade

Try here,

http://www.harley-davidson-hangout.c...uild-pics.html

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  #4  
Old 27-09-2007, 12:08 PM
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kiwidave kiwidave is offline
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Re: Evo performance upgrade

www.nightrider.com is the definitive one-stop resource for tried and tested upgrades there....

There is some truth in the S&S route.

Remember.....it is *relatively* inexpensive to free up an extra 20bhp in your stock Evo. It costs a helluva lot more wedge to add the next 20bhp...or even 10bhp.

If you are these desperate for power, why not buy somebody's hotrodded Twin Cam? One with mods that cut out the troublesome issues.
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  #5  
Old 25-10-2007, 10:39 PM
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Simon Simon is offline
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Re: Evo performance upgrade

If you do go the S&S route I can recommend Matt down in Wales. He can probably help out with other options too.
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  #6  
Old 26-10-2007, 05:09 PM
grbrown grbrown is offline
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Re: Evo performance upgrade

Quote:
Originally Posted by kiwidave View Post
There is some truth in the S&S route.

Remember.....it is *relatively* inexpensive to free up an extra 20bhp in your stock Evo. It costs a helluva lot more wedge to add the next 20bhp...or even 10bhp.
I can vouch for that - my 1990 Glide now has a JIMS stroker kit, flowed heads and much more besides!
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  #7  
Old 26-10-2007, 06:19 PM
Kiwi
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Re: Evo performance upgrade

Quote:
Originally Posted by kiwidave View Post
Remember.....it is *relatively* inexpensive to free up an extra 20bhp in your stock Evo. It costs a helluva lot more wedge to add the next 20bhp...or even 10bhp.

.
words of wisdom there, it is very easy & cheap to extract 70 ponies at the back wheel out of an 80" evo, after that it is a question of how fast do you want to spend
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  #8  
Old 26-10-2007, 07:30 PM
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Strawhead Strawhead is offline
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Re: Evo performance upgrade

I havea 97 Fatty,

i went down all the usual routes of performance upgrades, cam, carb, mild head work, increase compression etc etc

two years ago i bought a set of S&S 3 5/8 barrels and had the heads completely reworked with new larger valves, bought 10:1 wiseco pistons. the engine was then completely stripped, balanced and put together as it should have been from the factory.

cost in the region of 2,000, it goes very well now but sometimes i wonder if it was worth the money. personally if i could do it again for a slightly larger outlay i could have either have bought a 4 1/2 or 4 5/8 stoker fly wheel and combined it with the bigger bore

or just gone down an either S&S or Ultima route for more or less the same sort of money and then sold a perfectly good evo motor to get some money back

so much to chose from, but get advice on what is a good package from some one like Matts

best of luck
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  #9  
Old 09-09-2009, 06:18 PM
Ade67
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Re: Evo performance upgrade

Quote:
Originally Posted by Kiwi View Post
words of wisdom there, it is very easy & cheap to extract 70 ponies at the back wheel out of an 80" evo, after that it is a question of how fast do you want to spend

How easy, what would i need to do?
Ade
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  #10  
Old 09-09-2009, 06:42 PM
grbrown grbrown is offline
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Cool Re: Evo performance upgrade

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Originally Posted by Ade67 View Post
How easy, what would i need to do?
Ade
Ade,

We really need to know your model and current state of tune. I should point out that since I posted above my engine has transmogrified into a S&S 107! So beware, you could be starting down a slippery slope with this tuning lark.

The simple things are a freeflow (does not have to be loud) exhaust system (or mufflers), ditto air filter such as Screamin Eagle, replacement cam, plus carb jet kit. The cam will substantially improve engine breathing, aided by the filter and exhaust, while the jet kit will improve air/fuel ratio. I would also add a new ignition module, to give improved timing curves over stock.
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