Fat Boy 4 Complete Exhaust System-Yamaha Warrior

INSTALLATION DUNCAN RACING
INSTRUCTIONS INTERNATIONAL, INC.
FAT BOY 4 COMPLETE EXHAUST SYSTEM

MODEL: Yamaha Warrior


1.Remove stock exhaust system; Retain stock head nuts.

2.Before starting your Fat Boy 4 installation. You must make sure that the cylinder head exhaust gasket is intact and in good condition (usually they stay in the cylinder head). Under normal conditions it is OK to reuse them. If they are missing or in need of replacement they may be purchased from your Yamaha Dealer Part # 3VD-14613-01-00. DO NOT RUN MACHINE WITHOUT EXHAUST GASKETS. It also a good idea to make sure that the exhaust studs mounted in cylinder head are in good shape. If there is any doubt of their condition. Replace.

3.Install Fat Boy 4 header pipe using stock oem head nuts. Do not tighten header at this time. Leave nuts a few turns loose.

4.You are now ready to install the Fat Boy 4 muffler/tail section. The tail section is secured to the Fat Boy 4 muffler at the factory before shipping. If these (4) 6mm stainless button head allen screws are ever loosened or removed they must be reinstalled with some form of medium strength thread lock (recommended Loctite 242 Blue).
Before sliding tail section onto header it is recommended to apply a thin coat of hi-temp silicone to the inside of the tail section (female side) approximately covering about ½” of the initial part of the tail pipe. This will keep exhaust from leaking at the slip-fit joint and make removing pipe in future easier.

5.Install the muffler mount bolt going into sub-frame and tighten securely.

6.Tighten header pipe. Make sure to tighten header nuts evenly in a criss-cross pattern.

7.AIR INDUCTION: For maximum performance DRI recommends installing a Pro Flow Air Cleaner kit (billet flange, K&N Filter, Outerwear) with air box lid removed.

8.Carburetor jetting must be changed, see below for additional recommendations

9.Additional Performance and Jetting Recommendations;

For the best performance using your NEW Fat Boy 4 it is recommended to use a Pro Flow Air Cleaner Flange system with either a K&N or Uni air filter. The kits are made by Pro Design and are sold through Duncan Racing. The K&N filter makes the best power and it is recommended to run air box with the lid removed.

Jetting Recommendations:
The following guidelines are for Warrior’s with the following type set-ups.

Sea Level Temperature between 60° and 90°

Fat Boy 4 Complete Exhaust System

Stock Engine Pro Flow Kit with K&N Air Filter Air Box Lid Removed.

Pilot stock
Needle stock
Main Jet: #152.5 to #155

*DRI has included at no charge the necessary jets for the above jetting changes with an extra main jet each way.

The above specs should be an excellent starting point for most installations.
Jetting should be checked after install.

Be careful not to run machine too lean-engine damage may result. Too rich power will be lost.

Jetting Notes:

Colder temperature requires richer settings.
Higher elevations cause engine to be low on compression and generally require leaner settings.
Air box lid on requires leaner settings than with lid off.



For more information contact:

Duncan Racing International, Inc.
10734 Kenney Street Suite A
Santee, CA 92071
USA
(619) 258-6306

Check our Website for additional Warrior Performance items.

www.duncanracing.com