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Exhaust Systems Honda® TRX 250EX

HMF Racing Full System Exhaust Instructions

For Models: TRX 250EX (2001-2010), TRX 250X (2011-2021)


!!! 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 between the factory head pipe and silencer.(See Figure #1)

Full System Exhaust Instructions - Figure 1

2. Support the silencer while removing the (2) mounting bolts.  Once the mounting bolts have been removed, carefully twist and pull the silencer back and off the headpipe and off the machine.  

3. Remove the (2) nuts securing the headpipe to the cylinder head.  Save these nuts they will be used later.  (See Figure #2)

Full System Exhaust Instructions - Figure 2

4. Remove the headpipe.  Inspect the round gasket that seals the headpipe to the cylinder head, it may stay in the cylinder head.  If worn or damaged replace with a new OEM gasket.


1. Loosely install the HMF headpipe using the original (2) nuts.  Do not tighten.(See Figure #3)

Full System Exhaust Instructions - Figure 3

2. Slide the provided #56 T-bolt Clamp over the inlet of the HMF silencer

3. Carefully install the silencer by sliding it over the HMF headpipe and lining up the hole in the mounting bracket of the HMF silencer with the rear silencer mounting location on the frame.

4. Loosely mount the silencer to the frame using the provided (1) M8-1.25x20 Hex Bolts, (1) 5/16" Fender Washer, and (1) 1/4" Flat Washer.  The larger Fender Washer should be placed between the HMF silencer bracket and frame of the vehicle.  Do not tighten.(See Figure #4)

Full System Exhaust Instructions - Figure 4

5. Check for proper alignment and clearance between the HMF exhaust and all other components, adjust as needed.

6. Tighten all hardware in the following order:

  • (2) Headpipe to cylinder nuts
  • Silencer mounting bolt
  • Headpipe to silencer clamp.

Final Notes:

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.

Updated 6/27/19


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