Briggs and Stratton Surging With new Carburetor - Lawn Mower Forums : Lawnmower Reviews, Repair, Pricing and Discussion Forum
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post #1 of 19 (permalink) Old 04-05-2020, 03:06 PM Thread Starter
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Briggs and Stratton Surging With new Carburetor

Hello,

I have been working on an old 1997 Snapper rear engine rider with a Briggs and Stratton 28N707 0173-01 15.5hp engine.

I had been experience a lot of issues with the carburetor including float, valve, gasket, and other various minor issues. I decided I might as well get a new carburetor and just replace the entire thing. So, I got one and installed it no problems. It cranked right up like it was brand new! I went and did about a quarter acre of mowing as a test to make sure all the other repairs I did on the mower were good. No issues. Ran like a champ until today. I cranked her up and the engine was surging, not terrible but definitely was a problem. It puzzled me a bit as I had put new fuel, new fuel filter, and a new carb on the thing but I thought maybe some debris in the fuel line got caught in one of the fuel jets or something. So, I took the carb off and cleaned it thoroughly with a wire and some carb cleaner. Everything was free and open, I thought that was odd - I expected something to be there. So, I put it back on the engine and made sure all the adjustments were set to default 1 1/2 turns. Cranked it up, oh my gosh - it was worse! Now I am a bit worried. I shut off the engine and thought for a bit, did some research - perhaps it is the governor, maybe it slipped or something.

I adjusted the governor back and forth, I can make it go away - the surging, but it is at a ridiculously high RPM at idle and unsafe speeds if I pushed the throttle. At this point I am a little confused at what could be causing this. I did try adjusting the idle speed and fuel jet to see if they made a difference, they did not. I did notice the governor arm was swinging back and forth, which is one of the reasons I thought maybe the governor wasn't aligned correctly.

Here are all the new parts I installed on the engine: Carburetor, governor spring, air filter, fuel filter, spark plug, magneto coil, and starter. I also did an oil change.

Here is a video showing what it sounds like (notice the governor arm):

Anyone have any ideas? Could it be a leaking gasket somewhere that got worse when I opened up the carburetor?

Thanks for the replies!

Last edited by micahmesser; 04-05-2020 at 03:27 PM.
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post #2 of 19 (permalink) Old 04-05-2020, 03:47 PM
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Water in gas may have settled, did u drain the tank before the new carb? May have to drop the carb bowl to make sure no water buildup


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post #3 of 19 (permalink) Old 04-05-2020, 04:58 PM Thread Starter
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Tried new gas after draining everything, seems to idle better but is still surging some. Increasing speed causes it to get worse. Video: https://youtu.be/nTTozIVgdNI
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post #4 of 19 (permalink) Old 04-07-2020, 02:36 PM
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The governor gear may be toast inside the engine.
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post #5 of 19 (permalink) Old 04-07-2020, 04:33 PM Thread Starter
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Originally Posted by youngmech View Post
The governor gear may be toast inside the engine.
Guess best option would be to take it down and check it out? Just seems odd that it was bad, got worse, then got better when I changed gas but it is still surging some. It use to work perfectly fine and after sitting it started doing this.
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post #6 of 19 (permalink) Old 04-07-2020, 11:07 PM
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sure seems like it's running lean...I had that happen with the real low costs China carbs on Ebay...but, yours did run fine at first...so a tiny piece of debris is in there now, I would assume...If it's not right at he main jet..you'll prolly have to replace the carb..again...or try cleaning again....IMO
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post #7 of 19 (permalink) Old 04-08-2020, 12:34 AM
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My guess would be a plugged idle jet. Think that is what I found on my pressure washer a few years ago when it started running like that at full throttle.
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post #8 of 19 (permalink) Old 04-08-2020, 01:31 AM
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Quote:
Originally Posted by micahmesser View Post
Hello,

I have been working on an old 1997 Snapper rear engine rider with a Briggs and Stratton 28N707 0173-01 15.5hp engine.

I had been experience a lot of issues with the carburetor including float, valve, gasket, and other various minor issues. I decided I might as well get a new carburetor and just replace the entire thing. So, I got one and installed it no problems. It cranked right up like it was brand new! I went and did about a quarter acre of mowing as a test to make sure all the other repairs I did on the mower were good. No issues. Ran like a champ until today. I cranked her up and the engine was surging, not terrible but definitely was a problem. It puzzled me a bit as I had put new fuel, new fuel filter, and a new carb on the thing but I thought maybe some debris in the fuel line got caught in one of the fuel jets or something. So, I took the carb off and cleaned it thoroughly with a wire and some carb cleaner. Everything was free and open, I thought that was odd - I expected something to be there. So, I put it back on the engine and made sure all the adjustments were set to default 1 1/2 turns. Cranked it up, oh my gosh - it was worse! Now I am a bit worried. I shut off the engine and thought for a bit, did some research - perhaps it is the governor, maybe it slipped or something.

I adjusted the governor back and forth, I can make it go away - the surging, but it is at a ridiculously high RPM at idle and unsafe speeds if I pushed the throttle. At this point I am a little confused at what could be causing this. I did try adjusting the idle speed and fuel jet to see if they made a difference, they did not. I did notice the governor arm was swinging back and forth, which is one of the reasons I thought maybe the governor wasn't aligned correctly.

Here are all the new parts I installed on the engine: Carburetor, governor spring, air filter, fuel filter, spark plug, magneto coil, and starter. I also did an oil change.

Here is a video showing what it sounds like (notice the governor arm): https://youtu.be/Ybms1isfwQA

Anyone have any ideas? Could it be a leaking gasket somewhere that got worse when I opened up the carburetor?

Thanks for the replies!
that sounds like you new carb sucked up some trash blocking a fuel passage, the surging is because its running lean with the blockage

did you install a new fuel line and inline filter with the new carb?

dirt or lose rubber coming loose in old fuel lines often happens when you disconnect and reconnect old fuel lines so its always best to do it all new and your only talking about a foot of fuel line

pull the carb and clean it, the blockage is gonna be on those tiny little holes more likely then the main jet so be sure to check for clear flow on all those with carb cleaner.

You can only learn if you ask the question, so there are no dumb questions.
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post #9 of 19 (permalink) Old 04-08-2020, 02:56 PM Thread Starter
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Quote:
Originally Posted by keakar View Post
that sounds like you new carb sucked up some trash blocking a fuel passage, the surging is because its running lean with the blockage

did you install a new fuel line and inline filter with the new carb?

dirt or lose rubber coming loose in old fuel lines often happens when you disconnect and reconnect old fuel lines so its always best to do it all new and your only talking about a foot of fuel line

pull the carb and clean it, the blockage is gonna be on those tiny little holes more likely then the main jet so be sure to check for clear flow on all those with carb cleaner.
I did replace the in-line fuel filter. I did not replace the fuel line, might be a next step for me. Maybe I will try grabbing some tubing and just running the fuel right into the carb to see what that does.

I will take the carb off again and clean it to see what happens.

I did buy some seafoam and added that to the fuel to assist with keeping any type of gunk from building up.

One thing I did note today that after about 2 minutes of running it would run well at idle for about 20-30 seconds then fall back to surging for 10-20 seconds then go back to fine. Could very well be small pieces of rubber getting caught in the jet and getting cleared only to be replaced by another little piece. When any throttle is added, it surges pretty bad which leads me to believe the jets are getting clogged, just frustrating taking the carb on and off again!

I will update after I clean it and try some new tubing.
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post #10 of 19 (permalink) Old 04-08-2020, 03:32 PM Thread Starter
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I took the carburetor off and cleaned it out. I discovered a few little bits of I think rubber in the bowl (Picture attached). I cleaned it again, completely. I used a small little wire and carb cleaner to make sure every little hole was clear. I re-attached it to the engine, hooked up a new fuel line to the tank, and re-attached the air filter. I started up the engine AND....IT WAS WORSE. Almost would die between revs. I tried adding throttle and that didn't help. At this point I am completely at a loss....
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