Another 801 fuel line thread

[Russ from Dustville]

Hi folks,

I'm slowly working to get an 841 started that hasn't run in 10 years. I replaced the (original?) plunger type fuel shutoff valve under the tank with an aftermarket screw type (drilled the rivet, replaced the o-ring). The original shutoff accepted a 5/16 flare fitting for the fuel line. The new one accepts a 1/4" flare.

The tractor came with an inline fuel filter in a 5/16 hose, without a sediment bowl. (I don't know if it actually ran that way or not.) I decided to replace the filter with a sediment bowl, since the consensus seems to be that inline filters restrict the flow too much on gravity fed systems. I ordered one to accept a 5/16" flare fitting, but the one that came takes 1/4. So now I have 1/4" flare sockets at the tank shutoff and at the sediment bowl housing.

First question -- is there a problem with running 1/4" fuel line all the way from tank to sediment bowl instead of 5/16? Is vapor lock more likely?

The banjo bolt on the new sediment filter is also way too big to fit into the carb fuel inlet. The inlet in the carb body is straight 3/8 x 24 thread. It came with a brass adapter that goes from F 1/4" flare down to M 3/8 x 24 machine thread. Screwed into the 1/4 flare fitting was a 1/4 tube that's flared out on the other end to fit in a 5/16 hose -- it looks old enough to be original.

So I'm thinking of tapping the carb body to accept the banjo bolt that I have. It's a 7/16 x 20 thread. There's plenty of meat there, and plenty of depth as well -- should be easy to get the threads deep enough for the bolt without hitting the jet down in the hole.

My 2nd question is -- does anybody see a reason why I shouldn't drill and tap?

The 3/8 x 24 fuel inlet is tiny. It doesn't look like this carb (M-S TSX-769) was set up for a sediment bowl to bolt directly on. Were some carbs meant to be used with an inline filter or a sediment bowl mounted somewhere else?

Thanks, Russ

 

[MarkB_MI]

I don't think you have the original carburetor on your tractor, hence the missing sediment bowl and cobbled-up flare/hose fitting. I don't think you have anything to lose by drilling and tapping the carb, since the alternative is to replace it. Assuming you can find the correct tap.

If you're not working your tractor hard, the 1/4 inch fuel line should be fine. FWIW, my shutoff valve is 1/4 inch (couldn't find the correct 5/16), so the first few inches of fuel line are 1/4 before going to 5/16.

 

[Hobo,NC]

Hi folks,

I'm slowly working to get an 841 started that hasn't run in 10 years. I replaced the (original?) plunger type fuel shutoff valve under the tank with an aftermarket screw type (drilled the rivet, replaced the o-ring). The original shutoff accepted a 5/16 flare fitting for the fuel line. The new one accepts a 1/4" flare.

The tractor came with an inline fuel filter in a 5/16 hose, without a sediment bowl. (I don't know if it actually ran that way or not.) I decided to replace the filter with a sediment bowl, since the consensus seems to be that inline filters restrict the flow too much on gravity fed systems. I ordered one to accept a 5/16" flare fitting, but the one that came takes 1/4. So now I have 1/4" flare sockets at the tank shutoff and at the sediment bowl housing.

First question -- is there a problem with running 1/4" fuel line all the way from tank to sediment bowl instead of 5/16? Is vapor lock more likely?

The banjo bolt on the new sediment filter is also way too big to fit into the carb fuel inlet. The inlet in the carb body is straight 3/8 x 24 thread. It came with a brass adapter that goes from F 1/4" flare down to M 3/8 x 24 machine thread. Screwed into the 1/4 flare fitting was a 1/4 tube that's flared out on the other end to fit in a 5/16 hose -- it looks old enough to be original.

So I'm thinking of tapping the carb body to accept the banjo bolt that I have. It's a 7/16 x 20 thread. There's plenty of meat there, and plenty of depth as well -- should be easy to get the threads deep enough for the bolt without hitting the jet down in the hole.

My 2nd question is -- does anybody see a reason why I shouldn't drill and tap?

The 3/8 x 24 fuel inlet is tiny. It doesn't look like this carb (M-S TSX-769) was set up for a sediment bowl to bolt directly on. Were some carbs meant to be used with an inline filter or a sediment bowl mounted somewhere else?

Thanks, Russ

I thought oem carb was 3/8 X 24.

Normal Operation: Even a clean fuel filter creates a slight, engineered resistance as gasoline passes through its internal pleated media to trap microscopic debris.

Clogged or Dirty Filter: Over time, trapped rust, dirt, and sediment reduce the open surface area. As the blockage worsens, the filter chokes off the volume of gas passing through to the engine.

The consensus is not always correct. A fuel filter does just that filters the fuel once it gets contaminated with what it filtered out of the fuel it gets restricted. It did its job replace it and correct the contamination issue life will be good.

 

[showcrop]

First, vapor lock is nearly entirely an internet myth. It describes a condition that takes place with engine block mounted mechanical fuel pumps, not gravity flow systems. Yes, the 1/4 tubing is not original. 801s used 5/16, though it is highly unlikely that you would ever over draw the 1/4 tubing. The OEM tube used a 5 inch long rubber portion to protect from vibration. If you can't get past fear of "vapor lock", simply slit a five inch long piece of rubber fuel line and slip it over your steel line where it passes through the manifold as insulation.