Description
Thunderheader Black 2-into-1 High Performance Exhaust System – 1039B
New design for 2020 accommodates both 12mm and 18mm O2 sensors with the included 18-12mm reducers for expanded fitments
New 1039 manufacturer’s number replaces old 1031 and 1035
Designed to give maximum horsepower without sacrificing low-end torque
2-into-1 systems with patented collector design that directs spent exhaust gases in a spiral motion through four acoustical dampening chambers
Exhaust travels through these chambers at high velocity to scavenge spent exhaust gases from the combustion chamber and bring in a fresh charge of air/fuel mixture
Anti-reversion design works to impede reverse flow through the system — reverse flow can contaminate the incoming fuel/air mixture, which reduces performance and throttle response
As reverse flow enters the collector, the diffuser deflects it through vents; the pyramidal trap and apertures impede the reverse flow, allowing time for the exhaust valve to close
Flow director has equal area at each end, allowing exhaust gases to travel at a constant velocity over the entire length to improve exhaust scavenging
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.
Specifications
Color Black
Mfg #: 1039B
Part #: 4407264
Style Tapered Tip
Type 2-Into-1 System
Units Each
Weight 22.40 lbs
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