Introducing the Thunderheader Black 2-into-1 High Performance Exhaust System - 1039B! Backed by a new design for 2020, this exhaust system takes your bike's performance to the next level, all while offering an expanded fitment range.

The new 1039 manufacturer's number replaces the old 1031 and 1035, ensuring you have the latest and most advanced technology at your disposal. With Thunderheader, you can expect maximum horsepower gains without sacrificing low-end torque. It's the best of both worlds.

The 2-into-1 design of this exhaust system is complemented by a patented collector design. By directing spent exhaust gases in a spiral motion through four acoustical dampening chambers, Thunderheader maximizes efficiency. As the exhaust gases travel through these chambers at high velocity, they scavenge spent exhaust gases from the combustion chamber, creating space for a fresh charge of the air/fuel mixture.

What sets the Thunderheader apart is its anti-reversion design. This innovative feature prevents reverse flow through the system, which can contaminate the incoming fuel/air mixture, leading to reduced performance and throttle response. As reverse flow enters the collector, the diffuser deflects it through vents, while the pyramidal trap and apertures impede the reverse flow, allowing ample time for the exhaust valve to close.

The flow director of this exhaust system is designed for optimal performance. With equal area at each end, it ensures that exhaust gases travel at a constant velocity over the entire length. This results in improved exhaust scavenging, allowing your bike to perform at its peak.

Upgrade your ride with the Thunderheader Black 2-into-1 High Performance Exhaust System - 1039B. Unleash the true power of your bike while enjoying enhanced throttle response and a performance-driven riding experience. Trust Thunderheader to deliver the performance you desire.

Don't settle for less when it comes to performance. Choose the Thunderheader 2-into-1 High Performance Exhaust System and feel the power unleashed. Order now and experience the Thunderheader advantage for yourself!

Shop now and elevate your bike's performance to new heights!

• For heat shields, order the following:
  14 in. Top Front: 25-1725
  23 in. Top Rear: 25-1724
  13-1/2 in. Collector - 25-1723

For the best performance, A free-flowing air cleaner and adjustable fuel management system is recommended with this pipe.

Included items:(1) Exhaust header
(2) 18mm to 12mm Port reducers
(1) 5/16-18 x 1-1/4 in. Hex bolt
(4) 5/16 in. Plain washers
(3) 5/16 in. Lock washers
(3) 5/16-18 Nuts
(1) 3/4 in. Clamp
(2) 5/16-18 x 3/4 in. Hex bolts
(1) Mounting bracket

Not all products are legal for sale or use on pollution controlled vehicles. Check your local laws and the manufacturers information

There is no warranty on exhaust pipes and mufflers with regard to any discoloration. Discoloration (bluing) is the result of tuning characteristics, cam timing, carburetor jetting, overheating, etc., and is not caused by defective manufacturing. See the CHEMS/LUBES section for products that will help prevent or remove bluing.

Installation of a new exhaust system may change your motorcycles fuel-air mixture requirements. Please consult the exhaust manufacturer directly with questions regarding any modifications that may need to be made during, or after, installing their product. If a jet kit or fuel processor is recommended, see the FUEL/INTAKE sectionin. lock washers
(3) 5/16 in.-18 nuts
(1) Black steel mounting clamp
(2) 5/16 in.-18 x 3/4 in. hex head bolts
Instructions

The Air Resources Board (ARB) does not permit the use of aftermarket emission-related parts that alter the air/fuel ratio of an emission-controlled vehicle. Due to these legal restrictions this part cannot be shipped to California.