FORGOTTEN MOTOCROSS TECH: INSIDE SECRETS OF THE ICE CREAM CONE MUFFLER

On Jun 3, 2025 Last updated Jun 3, 2025

The 2008 and 2009 Yamaha YZ450 Fs were the only motocross bikes to ever come with a mechanical mufflers.

Motocross history is filled with examples of creative ideas that were heralded as ground-breaking, but, because of the rapid rate of change in development, sank into the swamp of forgotten technology. Although some are best left abandoned, others were truly innovative—if not ultimately successful. MXA reveals motocross’ tech trivia. Do you remember this ideas? Yamaha’s Ice Cream Cone muffler.

As a rule, motocross bikes, with the exception of the infamous 2008-09 Yamaha YZ450F ice cream cone muffler, do not use baffling, multiple venture chambers or other obstructions—although mechanical mufflers do appear on street bikes. Once the introductory thrill of ogling the downsized muffler on the 2008-2009 Yamaha YZ450F was over, most YZ450F racers wanted more power, improved throttle response and a less corked-up feel. From a sound standpoint, the stock 2008-09 YZ450F had a very innovative muffler. It used ice cream cone-shaped diffusers inside the muffler canister to reduce the energy of the engine’s pulses. The result was a quieter muffler than the year before (about one decibel), a lighter exhaust system (nine ounces) and a major loss of horsepower (over five horsepower at 6000 rpm).

The muffler has been cut-away to give you a clearer view of the ice cream cone diffusers. In function, the perf core does not have any openings (nor is the secondary cone painted yellow). The yellow part is the secondary cone. It is only perforated on the pointy end, the rest of this core is made of unperforated tubing.

The 2008 Yamaha YZ450F muffler was six inches shorter, 0.6 pounds lighter and packed with a special heat-resistant glass wool when compared to the 2007 muffler. To compensate for the shorty muffler, Yamaha increased the size of the 2008 YZ450F’s head pipe from 41.3mm to 45.0mm. Unlike a conventional muffler, which has a straight-thru “perf core,” the 2008 YZ450F muffler uses a normal, if slightly over-size, perf core, with two piggyback cones (made from perforated metal) inside the over-size perf core. Although the cones shapes are perforated, the second cone is attached to a section of unperforated tubing that runs over the last one-third of the muffler’s overall length.

Exhaust enters from the mid-pipe to the over-size perf core, where it is met by the first of the cone shapes. Some of the exhaust gases can bypass the first cone (around the outside diameter), but the majority must flow through the perforated cone, where it encounters the second cone (and repeats the process again). The muffler is packed with long strands of glass wool (there is no pillow-style packing). Yamaha did offer rebuild kits of the glass packs for $75. There also is no stainless steel mesh wrapped around the over-size perf core (as on the 2007 muffler).

On MXA’s priority list, a muffler has four tasks:

(1) Make the bike quieter. The ice cream cone muffler did just that bringing the YZ450F in at 97.5 dB (one decibel quieter than the 2007 muffler).

(2) Produce more power. The stock 2008-09 YZ450F muffler costs the big YZ-F both torque and ponies over the 2007 model. How much horsepower? Five horses

(3) Be as light as possible. Although it looks like it would be heavier, given all the metal parts inside it, the ice cream cone muffler was nine ounces lighter than the stock 2007 pipe

(4) The ice cream cone design achieved some of the goals that Yamaha set out for it, but the downsides were much greater. MXA’s test riders felt that the stock 2008-09 YZ450F YZ450F exhaust system was a massive marketing and performance mistake.

In 2016-2020 some of the Austrian KTM’s and Husqvarna’s came with ice cream cones inside their perf cores to knock off a decibel. It was not popular with racers.