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One of the first things many people want to do when they get a Harley is make it sound like a Harley and also run better. The cure is to install what is called a stage one kit.

For over thirty five years, Zipper’s Performance Products has been the premier performance resource for professional technicians, performance enthusiasts and racers of the Harley-Davidson motorcycles. Zipper’s Performance set the pace for the rest of the industry by being the first to develop reliable, pre-engineered Performance Kits for Harley engines and that is why I chose their parts for this project.

The installation of the Zippers Stage 1 Kit is something that can be done at home by anyone with average mechanical skills and some basic tools. There are also a couple of special tools that will make one or two of the steps go easier and I will mention them later.

While this install is on a trike it is basically the same for a two wheeler. On a trike the bolts holding the mufflers to the frame brackets are harder to get at.
Similar parts are available for other engines and years.

Having a shop manual for your specific motorcycle is recommended as well as following all safety procedures.

Start off by removing the right front floor board. Remove heat shields (it's good to spray the clamp fasteners with WD-40 and let them set overnight). Remove the bolts holding the mufflers to the brackets with a 1/2 inch box wrench or socket.

Loosen the clamp that holds the muffler to the pipe and move the muffler up and down and side to side until it is loose enough to pull off the pipe.

Remove the two bolts holding the crossover pipe to the oil pan and then the clamp holding it to the header, move up and down until it loosens and then remove.

I spray a little penetrating oil on the nuts holding the header pipe to the engine and use a 1/2-inch socket with a 1/4-inch drive, extension and ratchet to remove the nuts. I use a 1/4-drive and plenty of penetrating fluid so as to not damage or break a stud while removing the exhaust nuts.


Remove the header pipe from the engine and un-hook the O2 sensor wire from the harness under the right side cover and continue to remove header pipe.

Remove the retaining rings from the exhaust pipe and the exhaust flanges from the header pipe.

Remove and discard the exhaust port gaskets from the heads and install the new ones supplied with the kit. Using JIMS Tool number 788 makes this part of the job go easy.

With this kit the header pipe support bracket mounted under the transmission side cover is replaced. Using the bolts removed install the new bracket, add a couple drops of blue thread locker and torque to 13-18 Foot Pounds.

Install plugs for the 12 mm narrow band sensors into the header pipe. Install flanges and retaining rings on to header pipe, seat the front pipe into the port, pull back on the header and install the rear port. Using the nuts removed apply a little anti-seize to the threads and install. Snug - Do Not Fully Tighten. Install the carriage bolt in the clamp and start nut.

Torque the flange bolts holding the exhaust pipe to the head evenly until they are 100-120 Inch pounds and then P-Clamp nut to 25-28 Foot Pounds.

Install the crossover pipe and tighten the mounting screws to the oil pan to 84-132 inch Pounds and then the pinch bolt to 76 inch pounds.

On Trike models install pipe extensions.

Install mufflers and tighten all hardware.

Install Heat Shields being careful not to get fingerprints on shields. Clean with soap and water if you do.

Re-Install right front floorboard.

Time To Install The Thunder Max Tuner

ThunderMax Benefits Include:
•Easy to Install & Simple to Use

•Increased Engine Performance & Motorcycle Rideability
•Cooler, Smoother Running Engine
•Adjustable Idle Speed & Rev Limit Control
•No Dyno Required - Automatically Tunes for Riding Style & Riding Conditions
•Never Outgrow It - Easily Accomodates Bike Changes (Pipes, Cams, and More)
•100% Engineered & Made in the USA
•3-Year Factory Limited Warranty

Remove the left side cover and remove the main 50 amp fuse.

Install the new Thunder Max 18mm wide-band sensors into the header pipe. Bottom out and slightly tighten. Do not over tighten, because if you ever have to take them out there may be an issue. The washer on the sensor provides a good seal. There is a special tool to install sensors.

If you do not have a sensor socket you can use a 7/8 Crows Foot 3/8 drive.

Route the front sensor lead along the cross brace on the frame in front of the engine and down the lower frame rail on the right side of the motorcycle.

Route the rear sensor lead between the transmission top cover and the starter towards the ABS caddy located under the right side cover.

Remove the factory ECM located under the seat by spreading the clips holding it and lift up. Being careful pull back on the connector locks making sure they fully release and remove the three connectors.

Route the Auto Tune harness through the opening on the right side of the frame and towards the caddy.
Apply dielectric grease to the harness plug and noting the slot and tab install the cable into the Thunder Max seat fully and tighten screws.

Apply dielectric grease to the three stock connectors. Notice the connectors are different colors and the Thunder Max specifies where they are to be connected. Because of this guide, the harness is it is fool proof. Take Care to Install Plugs Fully and push in the Red Locking Tabs.

Once all three harness plugs are connected, place the Thunder Max into the ECM caddy.

Connect the oxygen sensor harnesses to the Auto Tune Harness making sure they are clear of moving parts and excessive heat. Re-install the 50A Fuse.

The Thunder Max comes with excellent instructions and a CD you can downloaded into a computer and use to set it up for your motorcycle and to also make changes if you decide later to do other modifications. Because I ordered the Thunder Max from Zipper's Performance it came pre-programed for this motorcycle.

Install the warning label about removing the main fuse before disconnecting battery cables and re-install the seat. This warning is to inform anyone who may work on the motorcycle in the future that a Thunder Max has been installed.


Remove the existing air cleaner cover using a 5/16 Allen, using a number 27 Torx remove the three screws holding the backing plate to the throttle body and then with a 7/16 socket remove the breather bolts.

Do Not Remove The Head To Head Throttle Body Support Bracket.

Clean the threads of the breather bolts, add blue thread locker and install them through the breather spacer and torque to 22-24 Foot Pounds

Apply blue thread locker to the three supplied stanchions and position the new backing plate to the throttle body using the new supplied gasket. Torque three stanchions to 85-90 Inch Pounds.

Re-install original breather hose to bolt nipples. Put the new air cleaner in place and install the original cover mounting plate with the new screws supplied after you have put a drop of blue thread locker on them. Tighten screws to 40-60 inch pounds.

Re-install the original factory cover with original screw with blue thread locker on the threads and torque to 36-60 inch pounds.

Turn the key on and wait a few seconds until the Thunder Max has booted. Start the engine and let run to normal operating temperature. The tuner has already started to make adjustments to your engine and will continue to do so for the next 50 miles or so. It will also Auto Tune as you ride around the country.

Test ride the motorcycle and feel the new power and sound as the tuner continues makes adjustments. Sweet.

Contact Zippers Performance for these and other fine products for your motorcycle.




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