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Exhaust Systems Yamaha® Grizzly 660

HMF Racing Yamaha / Grizzly 660 / Slip-On / Performance Series

For Models: Grizzly 660 (2002-2008)


!!! WARNING !!! Before working on your machine, make sure it is parked on a level surface with the transmission in park and/or the parking brake engaged. 

Do not work on any machine with a hot engine or exhaust.  Allow time for all parts to cool in order to reduce the risk of burns.

Blackout Exhausts: Take care not to get grease or oils on the exhaust.  Cleaning our Blackout exhaust with harsh solvents, abrasives, or pressure washers will remove the coating and is not covered under warranty

1. Loosen the clamp that holds the silencer and head pipe together.

2. Loosen the silencer mounting bolts.

3. Brace the back of the silencer with one hand and take the bolts the rest of the way out.

4. Pull back and twist until the silencer is removed.

5. Remove the gasket off of the head pipe it is not needed with the HMF exhaust. 


1. Slide the provided No. 58 T-Bolt Clamp over the slotted end of the provided S-Bend pipe.

2. Slide the slotted end of the S-Bend pipe over the stock head pipe.  Do not tighten the clamp.

3. Slide the HMF silencer over the previously installed S-Bend pipe.

4. Secure the silencer to the vehilce's frame using the provided (1) M8-1.25x20 Hex Bolt and (1) 3/8" Flat Washer.  

5. Check for proper alignment and clearance then tighten bolt securing the silencer to the frame then tighten the previouly installed clamp.

6. Install the provided (1) Long Spring between the S-Bend pipe and silencer.  (See Figure #1)

Yamaha / Grizzly 660 / Slip-On / Performance Series - Figure 1

Wipe off any fingerprints or markings using a soft cloth and mild detergent such as soap and water or glass cleaner without ammonia.  Once the exhaust heat cycles any oils left on the exhaust may permanently imprint.

If you received a stainless steel exhaust without the Blackout coating it is normal for the pipes to change color as they heat cycle.  

The HMF Blackout exhaust will smoke and put out an odor for the first full heat cycle as the coating goes through its final curing process.  It is recommended to allow this process to happen in a well ventilated area.

All systems will produce a smoke out the end cap after a short initial heat cycle, this is the packing material bedding in and is completely normal.


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