Wednesday, August 6, 2014

Noma Gran Prix Snow Blower -- Carburetor Service

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[To get to removal of the carburetor from the engine, see this post.]

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[For a detailed carburetor overhaul narrative, see this post.]

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Here's the carburetor off the engine.

Carburetor service is an art and a science that I'm by no means a master of. This post is only intended to give a few tips and hints that may be helpful for dealing with the subject carburetor.

Note the following:

  • If you're familiar with the carburetor from Tecumseh's TVS lawnmower engines, this carburetor is similar. The big differences are the presence of adjustable idle and high speed needle valves, and the absence of a primer bulb.
  • Before removing either needle valve, observe and record the number of turns required to gently close it. That will give you an initial adjustment point to get you going after re-installing the carburetor. Tecumseh's default setting is 1 1/2 turns for the high speed needle; 1 turn for the idle needle.
  • The float bowl's fastener is 7/16" hex.
  • I never disturb a welch plug, or a throttle or choke butterfly, unless there's a pressing reason to.
  • Blowing compressed air into the fuel inlet fitting will dislodge the float valve's resilient seat. That's helpful when you mean to replace the seat; it can be disastrous if you don't have a spare seat on hand, and the seat takes off for parts unknown.
  • The fuel filtering at the fuel tank's outlet nipple is fairly effective, and there shouldn't be any big particles inside the carburetor that could plug an orifice. A good flush and rinse with solvent in a parts washer, and a blow-off with compressed air, are all that a carburetor usually needs in the way of cleaning.
  • Float level is easily gauged by eye. If the float is level/parallel with the upper casting's lower flange when the float valve is closed, that's close enough.
  • Lubricate all threads at reassembly with WD-40.
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