Petromax Connection Body Rapid Preheater HK350/HK500

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The Petromax connection body is the pre-assembled three-part brass subassembly on the Rapid preheater of the HK350 and HK500. It connects the tank-side Rapid area with the other preheater parts and is already delivered fully assembled here. Nozzle, nozzle nut, toggle lever, flame guard tube, and the complete Rapid preheater are separate components from it.

pre-assembled three-part connection body assembly
made of brass, total weight 24 g
for Petromax HK350 and HK500
part of the pressure-loaded Rapid preheater
not a complete Rapid preheater



What role does the connection body play in the Rapid system?
The Rapid preheater uses the pressure built up in the tank to feed kerosene to the Rapid nozzle. There, the fuel is atomized, mixed with air in the flame guard tube, and directed as a preheating flame toward the carburetor. The connection body forms the tank-side base on which other Rapid components are arranged.
Therefore, it is neither a visible cover nor a universal brass adapter. Its geometry and connections belong to the Rapid assembly of the large Petromax models HK350 and HK500. A mechanically similar component for HK150 or HK250 is not automatically interchangeable.

Product classification: Class: complete pre-assembled subassembly within a modular preheating system. Usable directly: only together with the other matching Rapid components and a compatible lamp. System chain: Tank → connection body → Rapid nozzle → flame guard tube → preheating flame. Compatibility: Petromax HK350 and HK500.
Three-part assembly instead of three loose parts
Petromax describes the connection body as a unit of three individual parts, which are already fully assembled in this article. This reduces uncertainty compared to a repair from several loose small parts and makes the assembly a sensible choice if the complete connection body is to be replaced.
Which three internal parts Petromax exactly assigns to this count on the current product page is not named there. Therefore, no individual parts are implied in the scope of delivery here. Anyone who only wants to replace a specific internal part should first clearly determine its designation and position based on the Petromax spare parts drawing.
Do not confuse with the complete Rapid preheater
The connection body is only the base within the Rapid preheater. The functional system includes other parts, including nozzle, nozzle nut, toggle lever, and flame guard tube. Depending on the version and assembly, suitable sealing points are also added.
If only the connection body is damaged and the other components are clearly intact, this subassembly avoids the unnecessary replacement of the entire Rapid. If, on the other hand, lever, nozzle, tube, and connection are damaged together or several parts are missing, the fully assembled Rapid preheater for HK350/HK500 is the clearer comparison option.
When is the connection body actually the source of the problem?
Problems with preheating can have many causes. A leaking
Connection area, damaged threads, or an incomplete connection body assembly indicate this spare part. A poor spray pattern initially points to the nozzle, screen, tank pressure, or downstream Rapid components. A weak preheating flame therefore does not automatically prove a defective connection body.
Also, in case of pressure loss, the sealing point must be assessed separately from the brass body. A new assembly does not fix a leak caused by a wrong, damaged, or improperly installed seal. Likewise, it does not eliminate a malfunction at the pump valve, pressure gauge, or any other pressure-bearing part of the lamp.
Compatibility: HK350/HK500, not all HK models
Petromax explicitly specifies this version for HK350 and HK500. Individual neighboring parts such as Rapid nozzle, screen, or flame guard tube may be approved for several HK sizes. This broader approval must not be transferred to the connection body.
For HK150 and HK250, different connection bodies or assemblies exist. Therefore, the lamp’s model size is always decisive, not just the visual similarity of the Rapid preheater.
Material and scope of delivery
1 × fully preassembled Petromax connection body for HK350/HK500
Confirmed: three-part, already assembled brass assembly with a total weight of 24 g.
Not included as part of this item: Rapid nozzle, nozzle nut, toggle lever, flame guard tube, or complete Rapid preheater.
Petromax does not publish dimensions on the current product page. Tightening torques are also not specified and must not be derived from general tables.
Safety when working on the pressurized system
Before any disassembly, the lamp must be completely cold and the tank pressure fully released. Fuel work must be done away from ignition sources. The Petromax manual recommends disassembling adjacent lamp and Rapid parts for replacement; if you cannot confidently identify the assembly, have the repair done by a professional.
After assembly, check fit and tightness according to the manufacturer’s instructions before the Rapid is ignited regularly. An unknown torque, sealant, or improvised threaded part is not a suitable shortcut on this pressure-bearing assembly.
Practical tips for a clear repair

Document the Rapid sequence before disassembly Photograph connection body, lever, nozzle, nut, and flame guard tube on the cold lamp. This keeps visible which neighboring parts were present and how they were arranged.

Don’t mix spray pattern and connection problem If the problem is a clogged nozzle opening, the nozzle is the relevant part. The connection body only becomes a repair decision if its assembly or connection is affected.

Evaluate sealing surfaces separately from the brass body A leak can occur at the seal even if the connection body is mechanically intact. Check both positions individually instead of automatically replacing the larger assembly.

Record model size before comparing parts Note HK350 or HK500 before ordering. The multi-model approval of nozzle and flame guard tube does not make the connection body compatible with HK150/HK250.

Choose the complete assembly if several Rapid parts are missing If toggle lever, nozzle, or flame guard tube are also missing, a complete Rapid preheater reduces the risk of an incomplete combination of individual components.

Black-Raptor short summary: Buy if: the complete three-part connection body on the Rapid preheater of an HK350 or HK500 needs to be replaced. Don’t buy if: you have an HK150/HK250, only need a nozzle or seal, or the entire Rapid preheater is incomplete.

Suitable Rapid components and complete alternative:
Petromax Rapid preheater HK350/HK500 complete
Petromax nozzle for the Rapid preheater
Petromax Flam
Muzzle protector for the Rapid preheater
Petromax lead seal for carburetor and Rapid preheater
Petromax Viton seal for carburetor and Rapid preheater

Technical data

Manufacturer: Petromax

Product type: pre-assembled connection body

System: Rapid preheater

Compatibility: HK350 and HK500

Construction: three already assembled individual parts

Material: brass

Weight: 24 g

Scope of delivery: one complete connection body assembly

FAQ
Is the connection body already assembled? Yes. Petromax delivers the three-part subassembly fully assembled.
Is the complete Rapid preheater included? No. Nozzle, nozzle nut, rocker lever, and muzzle protector are not automatically included with this item.
Does the assembly fit the HK250? No. This version is exclusively specified for HK350 and HK500.
Are the three internal individual parts available separately? Petromax confirms separate replaceability. However, the current product page does not name their three designations; they must be identified via the spare parts diagram.
Does replacing it fix every Rapid problem? No. Nozzle, screen, seal, tank pressure, rocker lever, and muzzle protector can cause faults independently.