SINISTER powersports | Technical

Check out the official sound of the off road

HMF has been developing after market exhaust systems for nearly two decades.

Whether your machine is built for the dirt or pavement, their exhaust systems substantially increase the horse power and torque on your machine while adding an incredibly aggressive sound.

SINISTER powersports are GASSED to be able to say we are the SOLE distributors of HMF and IQ Racing products here in the UK.

How can I make my exhaust look like new again?

Turns out, most of the luster of your exhaust lies in a small green pad with a rough surface;

Scotch Brite ®.

This little green monster can be used to take off a ton of dirt and grime from your exhaust system, and leaves it a nice revived shine.

Of course, this only works on the brushed aluminium and stainless steel cans.

Don't go takin' this Scotch Brite ® to work on your beautifully powder coated exhaust shells, or the Blackout head pipe.

That's just plain stupid.

Enjoy, Brraap.

My exhaust has changed colour, what does this mean?

Often times, users can experience exhaust discoloration due to improper tuning, engine malfunction or after-market additions.

It's important to keep in mind that steel exhibits different oxidation and incandescent colours depending its temperature.

Below 800°F it will have oxidation coloration.

Above 800°F and it will display incandescent (glowing) coloration.

Below is a chart that can be used as a general guide for determining how hot your engine or exhaust system is running. This is not an accurate way to determine header pipe or exhaust gas temperature. Use this as an indicator to check the temperature by a more accurate method.

If your pipe is blue or bluish grey when it is cold (the hottest oxidation colours), it may actually be much hotter when running. After the pipe cools from glowing hot, the oxidation colour will remain.

A good exhaust gas temperature at the exhaust port is 1250°F (blood to cherry red). In general, glowing is acceptable for the first 6-8 inches after the exhaust port. When cool, the head pipe shouldn't be blue more than 10 inches from the exhaust port.

No part of a slip on exhaust should ever be blue.

If your exhaust is displaying of the above conditions, your engine is running extremely lean. You most likely need to richen your jetting/fuel map. If this does not fix your problem, you should look for an air leak after the carburetor/throttle body.

If you need help with any of the information in this article, please contact our one of our support team 0151 356 3021.

How do I repack my exhaust?

We get this question a lot here.

Typically, the average rider will need to repack their exhaust after about 40-50 hours of riding. This can vary however depending on the type of riding.

More aggressive race machines are going to need to repack more often than the average trail rider.

Repacking your exhaust requires an air rivet gun or an automotive style riveter. A small hand riveter will not work for this.

If you would like us to repack your exhaust system, see our Repair Services for details.

Download the HMF Repack instructions here

Installation Instructions:

Step 1: Using a marker, draw a line representing the clock position of the inlet and exhaust.

Step 2: On the inlet side only, tap all the rivets until the stem drops.

Step 3: On the inlet side only, drill out each rivet.

Step 4: Using a rubber mallet, tap the exhaust shell to remove the inlet.

Step 5: Using a 4mm alan key, loosen the alan screws on the end cap.

Step 6: With the exhaust shell removed, discard of the old packing and wrap the new packing around the core.

Step 7: When wrapping the packing around the core, make sure to make it as snug as possible.

Step 8: Tuck the packing underneath the inlet.

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