Snapper M301019BE only runs on choke

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  #1  
Old 10-16-14, 05:15 PM
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Snapper M301019BE only runs on choke

Hello All!

I have a Snapper M301019BE with a 10HP Briggs & Stratton 28b707-1153-E1 engine. It uses a gravity fed Walbro LMT carb, but I'm not sure which model exactly. The Briggs part # is 498027 (but apparently that part number applies to multiple carbs).

Anyway, I recently acquired this mower. It had been stored with fuel in the tank/carb, so the first thing that I did was to remove the carb and rebuild it with kit# 497481. I cleaned the carb in my ultrasonic cleaner, then used compressed carb cleaner, and blew all of the passageways clear with compressed air. As part of the rebuild process, I also removed and replaced the needle valve body and needle. Additionally, I replaced the old fuel line, added a new fuel filter, as well as a fuel shut off valve.

I replaced the newly cleaned and rebuild carb and the engine started easily. However, it will only run choked and at full throttle (if I back the choke off very slowly). When bringing the throttle back to idle, the engine sputters and fine gas droplets shoot out of the carb where the air intake would normally connect.

So, that's where I am, and I'm not exactly sure what process to use in order to troubleshoot the issue further.

Any and all help is appreciated!
 
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  #2  
Old 10-16-14, 08:10 PM
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The carburetor is still clogged, probably in the main jet. Use spray carb cleaner and a wire to poke through the holes up the tube in the center of the carb, and if there is a hole in the side of that tube, make sure it is completely open too.
 
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Old 10-16-14, 09:04 PM
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Thank you for the advice, Cheese. If the main jet is the same thing as the emulsion tube (the brass tube with multiple holes that essentially runs from bowl into the venturi) then I replaced it with the one from the carb kit. It's brand new and definitely not clogged.

The more I look at this, the more I wonder if my issues are the result of an incorrect carb kit. The kit that I used was purchased from a dealer, but it appears to go on the lmt 62, 63, 64, and 65 carbs - however, I *think* my carb is a model 5 which has a different repair kit associated with it here:

http://www.briggsandstratton.com/us/...=MS0153_LO.pdf

I don't see a number stamped on the carb mounting plate where walbro says the model # should be, but there is a 5 stamped on the carb body.
 
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Old 10-16-14, 09:54 PM
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It still should run without full choke. Look at the post where the emulsion tube goes in... is there a jet in the side of it? If so, this may be restricted.
 
  #5  
Old 10-17-14, 09:37 AM
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You might have an air leak, with the engine running spray/dribble some carb/brake parts cleaner along the mating surfaces of the intake, if the engine tempo changes you have a leak. I had one of those with a hair line crack in the intake about drove me nuts. Have a good one. Geo
 
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Old 10-17-14, 06:18 PM
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Ok. I've inspected everything again (including checking for air leaks), and I can't find a thing wrong with the carb - EXCEPT one thing! The carb rebuild kit sold to me by a dealer is 497481, and that kit contained a fuel nozzle (emusion tube). I replaced the one in the carb with the new one.

I did some calling around today and spoke with people from Walbro, and B&S. I found out that the carb on my engine is 697171, and uses a different rebuild kit than what I was provided. I further compared the new fuel nozzle against my old one (even though my old one is unusable now), and they are definitely different. I think the design difference is resulting in an improper rate of fuel flow. I have ordered the correct nozzle, and will have it installed next week.

It is also worth noting that the rebuild kit for my carb (697884) doesn't come with a replacement fuel nozzle / emulsion tube. Perhaps that's to help avoid issues like this one?
 
  #7  
Old 10-18-14, 12:20 PM
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Apparently you had to destroy the old tube in getting it out? The tubes are press fitted and that keeps them in place?

If so, the thing you may want to check is how tight the new tube fits to make sure it would be air tight. That is critical for the draw of fuel up the tube. Any amount of air leak will affect the amount of fuel drawn into carb throat and can result in the problem you have - an overly lean mixture needing the extra choke.

Should you find there is a problem, you can put a little gas tank epoxy on the tube away from the end. It only takes a little smear that will bead up when you press in the tube. Make sure everything is clean and dry. Prepare the surfaces with something like acetone.
 
  #8  
Old 10-18-14, 10:26 PM
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Yes, the soft brass of the fuel nozzle didn't hold up well, even under a perfectly sized screwdriver. When I say the design of these tubes is different, I mean the location and number of fuel ports is different on each one. So, everything else aside, I don't see how this new emulsion tube could have ever worked.

I really appreciate the tip on how to eliminate air leaks around the nozzle though. I'm definitely filing that bit of knowledge away!

I will confirm on my findings once I get the new fuel tube.
 
  #9  
Old 10-19-14, 06:52 AM
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It's a screw in type, then so it should seat itself and although it's something to check it shouldn't be an issue.

Usually the metering of the fuel is done through a main and idle circuit. Each is metered with one jet. The emulsion design is different animal, though.
It works to add air to the fuel past the metering phase. Differences in it other than the metering part would likely affect the performance.

Then there's usually a choke circuit. But over the years a lot of variations have shown up with different chokes, primers, throttle controls, etc. You just about have to go by what you have rather than other models.
 

Last edited by marbobj; 10-19-14 at 09:10 AM.
  #10  
Old 10-19-14, 04:34 PM
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We have joy, folks! Once the proper emulsion tube (fuel nozzle) was installed, the motor is acting like it should. Now I am troubleshooting a different issue. I will start another thread for that topic.

Thank you for the insight and the tips!
 
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