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Briggs 21.5hp not idling


martin1b's Avatar
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03-19-07, 10:17 AM   #1  
Briggs 21.5hp not idling

I have a 21.5 hp briggs in a craftsman mower. It's not idling correctly. It sounds like it's about out of gas. I can give it some choke and it will even out for the most part but it sounds like it's running a tad rich. I pulled the carb and everything looks nice and clean. I had someone who knows a little more about carbs pull then off and look at them. We cleaned them with carb cleaner and reassembled. It still runs uneven. We even went so far as to put a little silicone on the outside of the joints in case there was a leak. Runs the same.

Any ideas?

Bill

 
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puey61's Avatar
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03-19-07, 12:06 PM   #2  
We'll need more information first. In your particular case, we need engine ID numbers (model, type and code) and we would also like (but not necessarily need) your chassis ID numbers (model and serial). This tells us what you have specifically and helps us help you. Initially, I'd say you have a idle jet that is restricted, since you say that it idles poorly. How does the engine run at anything above idle speed? And since you can smooth out the performance with some choke, this tells me that you have a lean condition, not a rich condition. Again, if I had the engine ID numbers I could walk you through the correct procedure, so post back in this thread with that information.

 
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03-22-07, 06:49 PM   #3  
Briggs 21.5hp not idling

Found the information-

The engine info is as follows:
Model : 445777
Type : 0154e1
Code : 0104308H

Chassis is as follows:
Model : 917.272462
SN : 042202d002800

Just so I clarify, the choke doesn't totally clear it up. However, it is the closest to a clean run at full throttle. Also, not sure if I mentioned it before but this is a twin.

Also, are the engines normally pretty loud on these? I'm used to my dad's cub cadet with a kohler on it and it was pretty quiet compared to this. I bought a new muffler thinking that something was wrong but it's still pretty loud.

Any ideas?

TIA!!

Bill

 
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03-23-07, 06:24 PM   #4  
I'm not sure what carb you have but in similar situations, I sometimes remove the idle jet and blow the bore out with WD-40 pressed tightly into the carb. Sometimes the pressure of the WD-40 is enough to clean it out so you can put the idle jet back in snug, then back it out 1 1/2 turns or so as required to get good idle.

Sometimes this works and sometimes it doesn't but it can be a real timesaver when it does work.

 
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03-24-07, 06:23 AM   #5  
Azis
I dont think your carb has an idle mixture adjustment. Also since you claim the problem is not only at idle, I would suspect this is not the problem. Make sure you have sufficient fuel flow to the carb. Check the fuel filter and fuel lines.
Make sure the fuel nozzle in the carb is clean as well. Remove the screw that holds the bowl on, then look up in the tube that screw threads into. You should see another screw with a slot or allen perhaps. Remove this and clean.
You do NOT want or need to use silicone on the carb. If this does not show improvement then the carb body may need to be soaked in some good carb cleaner.
One other thing since you mention this is a twin. Make sure that both cylinders are firing. Using an insulated pair of pliers or the like, and keeping your free hand behind your back, start and run the engine and remove one plug wire at a time and note any difference in rpm or sound or....

 
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03-24-07, 09:16 AM   #6  
Now that you mention it, a few more details come to mind. I have replaced the fuel filter and the line that goes from the fuel filter to the carb. (It had the problem before I did this). I also took the carb apart and dipped it overnight in some carb dip. Same thing. You are on the money. There are hardly any adjustments to this carb. Both cylinders are firing.

My guess is that it's not a fuel delivery problem since it runs a fair amount better (put definitely not perfect) at full throttle when I give it some choke. But, that's just a guess. Is a leak totally out of the question? Is there a way to test for a leak?


Side question: Since it has the gas tank in the back, does the fuel pump work off of vacuum from the crankcase?

 
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03-24-07, 10:52 AM   #7  
Azis
At some point it almost has to be a fuel restriction/delivery. When you use the choke you are reducing the amount of air the carb intakes therefore richening the fuel/air mixture.
If you had a problem with one part of the fuel line, it would only stand to reason that the rest of the line is in no better shape.
Since you have had the carb apart, perhaps installing a rebuild kit would be in order. You can get the diaphragms for the fuel pump as well.

If there was a leak causing this most likely it would not be on the carb, but perhaps at the intake where the carb mounts.
Check the vent line from the fuel pump to the engine as well. Make sure its in good shape and both fittings are snug.

 
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