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Stage 3 EVO

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Old Sep 15, 2005 | 12:01 AM
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Default Stage 3 EVO

Stage 3 Modifications
Building a 82 horsepower 1340 Evolution engine

Performance and Technical information on Stage 3 modifications to a Harley-Davidson 1340 Evolution motorcycle engine.
Building the ultimate street bike engine
or
How to get 82HP from your 1340 Evolution engine.


The camshaft in your bike has been upgraded. If you have made these Stage 2 changes to your bike and are still looking for more power, you may be ready for a Stage 3 engine where modifications can begin to get a little more complicated. Better flowing heads and increased compression ratios are the way that this is usually done.

There are many companies out there that are competing for the dollars that Harley-Davidson owners are willing to spend on their bikes. As an owner, you will be bombarded with a vast array of promises, claims and inaccuracies in an effort to separate you from your money. Reading between the lines on many of the performance claims can be bewildering.

Does the Harley-Davidson world need another bolt together engine modification article? We decided it does, since the results obtained by the engine upgrades listed here provided significantly better results than those documented by the popular magazines aimed at the V-Twin crowd. The Motorcycle Performance Guide staff continues to obtain better results than the "experts" in the press.

How to build your own Stage Three engine

This Stage Three engine did not involve any internal changes to the engine other than replacing the OEM heads with the Screamin Eagle 1340 EVO heads. All modifications are made by bolt-on changes. Some special tools and training is required to perform these modifications. Unless you are a very good mechanic, it is recommended you find a competent shop to install the heads. For those of you that want to install the heads yourself, Motorcycle Performance Guide recommends you obtain the proper service manual for your bike.

Over the past several years we have installed and tested many manufacturers components. The list of parts used in building the ultimate 'bolt-on parts' engine is the end result of this testing. The best and least expensive of the individual components was selected an tested as a single package. The fact that virtually all the parts used for the project are from Harley-Davidson is a coincidence. There was no plan or idea to use mostly Screamin' Eagle parts for this project.

All the parts used are readily available through your Harley-Davidson Dealer. The components were installed and tested on a 1997 FXD Dyna Super Glide. No special tuning was performed to achieve the results listed. All components were installed according to the manufacturer instructions supplied.

Building your Stage 3 engine
Stage 1 improvements must be in place
Stage 2 improvements must be in place
Replace the OEM heads with the new Screamin Eagle Evolution heads
Change Oil and Filter
Install new spark plugs
Road test the bike
Dyno Tune the bike

The results of the Dyno testing are excellent as this bike's performance continues to improve. The test results showed the engine producing 81.7 horsepower @ 5700 RPM and 87.1 ft. lbs. of torque @ 3900 RPM. The long, flat power curve on this engine is ideal for street riding. There was an 18 horsepower increase over the Stage 1 results and an 8 horsepower increase over the Stage 2 engine. The engine is producing 28 horsepower more than a stock bike. Not bad for the relatively investment in time and money required to get these results.

Just how fast is fast enough is a matter of opinion. This 97 FXD was taken to the local drag strip in order to establish what sort of 1/4 mile times could be turned with this bike. The bike proved to be a potent Harley drag race bike by turning times in the 12:40 range with 105 MPH speeds. Considering the rider for this test is relatively inexperienced, it is expected that in the hands of an experienced racer, times in th
 
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Old Aug 23, 2008 | 10:16 PM
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I acquired a 1999 Heritage Softail from the dealer and it has Screamin Eagle Heads and was customized first rate, it seems. Would I be safe in assuming it had a factory or professionally done upgrade? The dealer is certain it was. Is the displacement still 1340? How do I get an effective tech manual for maintenance purposes?
 
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