SW's Backpacking stoves

A comparison between stove pumps from Optimus/Primus and MSR

One of the most important parts of a (pressurized) stove is the pump. American manufacturer MSR has received much flak for its plastic pumps which, according to numerous user reports, are prone to break. Swedish manufacturers Optimus and Primus both use the same (except for the connector) all metal pump. The pictures below show the pump that came with my MSR Whisperlite Internationale 600 and the pump used by both the Optimus NOVA, the Optimus No 11 Explorer and (though with a different connector) the Primus Himalaya Multi Fuel Stove as well as the Primus Himalaya Vari Fuel Stove.

The Optimus/Primus all metal (turned aluminum) pump to the left and the MSR plastic pump. The MSR plastic pump weighs 50 gram (just under 2 oz), the Optimus all metal pump weighs 110 gram (just under 4 oz). But even with the metal pump the Optimus NOVA weighs less than the MSR Dragonfly.

Close up of the threads and the gasket/O-ring used by the pumps. The metal pump has heavy-duty turned threads and a wide rubber gasket, the plastic pump has short and low threads and a thin O-ring. In my experience the O-ring used by MSR cracks more often than the wider gasket used by Primus/Optimus, causing dangerous leaks.

A close-up of the top of the MSR pump. It is held together by a bayonet mount using small lugs that are prone to break.

The Optimus/Primus pump is screwed together. In this picture you can see the knurled screw-on cap that holds the aluminum plunger in place. If you need to oil the leather pump washer you unscrew the cap to pull the entire plunger/washer assembly far enough out to enable it to be easily oiled. 

The quick connector used by Optimus is a commercially available connector rated at 1200A. It's fast to connect and disconnect, lightweight and extremely strong. A good example of using the best parts available instead of trying to invent the wheel twice. Primus use screw-on connectors, both for the Himalaya Multi Fuel and the Himalaya Vari Fuel (though two different designs since the Himalaya MFS is able to use butane/propane canisters too). 

The "slide in, hook on and hope it doesn't leak" design used by MSR is IMHO an inferior design. The brass end of the fuel line is slid into the fuel tube (the opening in the plastic pump) and is then held in place by the steel wire.

The bottom of the pumps. The all-metal pump is screwed together, the plastic pump is once again using a cheaper bayonet mount and small plastic lugs.

The top of the Optimus fuel bottle (the one used by Primus is similar apart from the color). A wide lip fits against the wide rubber gasket shown in the second picture from the top. The metal is thicker than that used in the MSR bottle below.

The top of the MSR (20 oz) fuel bottle. A thinner lip than that used by Optimus and Primus. The threads in the bottle are longer but the threads on the pump are far shorter (and lower) than those on the Optimus or Primus pump. The threads on the MSR pump are only half as long as the threads in the bottle. The threads in the Optimus fuel bottle are the same length as the ones on their metal pump.

NOTE! MSR fuel bottles now have a redesigned lip with a machined edge that is much narrower (sharper) than on the old bottles. The new bottles work fine with the O-ring used on MSR pumps, with a better seal than with the old bottles, but should not be used with Primus or Optimus pumps since the sharp lip on the new MSR bottles will cut through the gasket used by Optimus and Primus. So use MSR bottles with your MSR stove but Optimus or Primus fuel bottles with your Optimus or Primus stove!

The MSR pump. The newer pumps are grey with red parts, older pumps are grey with black parts. The difference between the two is, according to the MSR web site, only the addition of a stop nut under the control valve, presumably to keep the valve from falling out.

The Optimus pump.

© Svante Wendel 2000-2003