Saturday, October 25, 2014

Noma Gran Prix Snow Blower -- Fuel Supply Tubing Replacement

The fuel delivery tubing on my son's snow blower looks a little decrepit, so I aim to replace it with new tubing.

It might appear to a cursory glance that replacing the fuel supply tubing ought to be a breeze. It's not. The fuel supply tube is clamped in place at a point underneath the flywheel. The flywheel has to come off to enable tubing replacement.

One is reminded here of the old saying, "If it ain't broke, don't fix it." If I do any harm to the machine's flywheel, I'm going to powerfully wish that I'd left it alone.

On the other hand, if the tubing ruptures while my son is clearing his driveway this winter, I'm going to powerfully wish that I'd replaced the tubing.

On balance, I may as well proceed cautiously with replacing the tubing; it's not threatening to snow yet, so I should have time to deal with whatever may arise.

Replacement Tubing

This is the stuff that's needed.

It's 1/4" (0.250") inside diameter by approximately 7/16" outside diameter reinforced tubing. I get it by the foot from the local small engines repair place.

Tubing Access

Attend to the following:

  • Output Chute Rotation Shaft -- Disconnect its lower end and swing it out of the way to enable heater box removal.
  • Heater Box -- Remove it.
  • Primer Tube -- Disconnect it from the carburetor.
  • Throttle Control Plate Assembly -- Remove it. Note/mark which hole the governor link connects to.
  • Electric Starter Drive Entry Cover -- If there's no electric starter, there'll be a small cover where an electric starter's drive would enter the cooling shroud. Remove it.
  • Locomotion Ratio/Direction Control Rod -- Disconnect its bottom end and let it dangle. (1/2" hex nut; 7/16" ball-stud hex.)
  • Cooling Shroud -- Remove it. (7/16" and 1/2" socket wrenches.)
  • Starter Clutch Cup -- Remove it. (15/16" socket wrench.) Put the nut back on the shaft part way, so the flywheel can't tumble when you break it loose.)
  • Flywheel -- You have clearance to get a 6", three-jaw puller in place, like so.

Hook the puller's jaws under the outboard rim of the flywheel, not under the starter ring gear.

Try to position the puller's jaws so they're directly opposite cooling fins, as is the jaw in the above photo. You want the puller to be acting on the strongest possible points on the flywheel's rim.

Tighten the puller, and whack the puller's screw head with a club hammer. If the flywheel doesn't break loose right away, keep tightening and whacking until it does.

With the flywheel off, you have easy access to the retaining plate that clamps the fuel delivery tube in place.

Two 3/8" hex head screws hold the plate in place. Remove those and the plate, and nothing is in the way of  replacing the tubing run.

The short, vertical length of tubing from the tank to the shut-off valve is 1 1/2" long. The long, horizontal length of tubing is 14" long.

The tubing is a snug fit at all the nipples, but it's especially snug on the fuel tank's outlet nipple. A little WD-40 on the nipples makes the tubing easier to install.

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