Posted: 4/2/2012 8:56:09 AM EDT
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The engine to my garden tractor has been revving up and down when the throttle is less than full. The engine is a 19.5 hp Briggs and Stratton.
This weekend I took apart and cleaned the carburettor, but after reassembling and firing up the tractor it is still doing the same thing. Now, admittedly I have no idea how to clean a carburettor, so I just took it apart and sprayed carb cleaner everywhere. The funny thing is, the engine will not do this when the air filter is removed. When an air filter is on but not covered (the carb is open to air, the air filter is just sitting there uncovered), it will do it…... So this tells me something is wrong within the carburettor related to air flow???? Any help would be great. |
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Clean/put a new air filter on it. Report back. It may end up being a process of elimination. Does it stay running or eventually die? Does it do it underpower or at idle? Does tall grass bog it down and kill it? Stays running. It does not do it at full throttle (like when mowing). |
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Thanks....I'll cruze through that forum and see what I can find. |
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The governor is hunting. Governors work by balancing spring force (opens throttle) against centrifugal force (closes throttle). If you installed the spring(s) incorrectly, this could be the cause. Could also be mixture issue. But most likely it is a spring issue. It never did this before. This all started around the end of summer last year. I had never taken it apart prior to that. Maybe the springs are wearing out? |
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The governor is hunting. Governors work by balancing spring force (opens throttle) against centrifugal force (closes throttle). If you installed the spring(s) incorrectly, this could be the cause. Could also be mixture issue. But most likely it is a spring issue. It never did this before. This all started around the end of summer last year. I had never taken it apart prior to that. Maybe the springs are wearing out? Or the linkage is getting gummy. But... I'd look at the gas supply first. Things to check: the carburator float is sticking the fuel line is partially blocked jet is plugged check that you don't have contaminated gas or gunk in your fuel tank if there's a fuel filter it may be clogged |
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Get you a gallon can of Chem-Dip carburator and parts cleaner. Take the carb completely apart, placing the plastic pieces aside. Put the metal parts in the basket in the cleaner. Let soak for 30 minutes. Take the parts out and take a spray can of carb cleaner with the spray tube attached and spray it in all of the little holes in the carb, wearing eyepro of course. The spray cleaner will go through the passageways and spray out the exit hole. Do that to all parts. Clean all of the parts with carb cleaner to remove chem-dip. put back together, put on engine and adjust. Profit.
Did this to my troy-bilt weedeater and generator over the weekend. Both only ran at half-choke. Now they both run like scalded dogs... 
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The governor is hunting. Governors work by balancing spring force (opens throttle) against centrifugal force (closes throttle). If you installed the spring(s) incorrectly, this could be the cause. Could also be mixture issue. But most likely it is a spring issue. It never did this before. This all started around the end of summer last year. I had never taken it apart prior to that. Maybe the springs are wearing out? Or the linkage is getting gummy. But... I'd look at the gas supply first. Things to check: the carburator float is sticking the fuel line is partially blocked jet is plugged check that you don't have contaminated gas or gunk in your fuel tank if there's a fuel filter it may be clogged Fuel Filter is new....I'll try and check everything else you mention. |
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The governor is hunting. Governors work by balancing spring force (opens throttle) against centrifugal force (closes throttle). If you installed the spring(s) incorrectly, this could be the cause. Could also be mixture issue. But most likely it is a spring issue. It never did this before. This all started around the end of summer last year. I had never taken it apart prior to that. Maybe the springs are wearing out? Or the linkage is getting gummy. But... I'd look at the gas supply first. Things to check: the carburator float is sticking the fuel line is partially blocked jet is plugged check that you don't have contaminated gas or gunk in your fuel tank if there's a fuel filter it may be clogged Fuel Filter is new....I'll try and check everything else you mention. Clean the carb really good and it will probably fix it, since it runs at full power. |
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Briggs and Stratton carbs are pretty easy to work on, especially the single cylinder models. The bowls spin off, exposing the float and valve. The needles are Viton tipped, they are fine with ethanol gasoline. But the seats are brass which corrodes with ethanol. Use copper-dissolving bore cleaner, flushing with carb cleaner. The twin cylinder carbs are more complex due to parts count and linkage complexity. Both usually have a Mikuni fuel pump, check hoses (all three, suction, delivery and crankcase pressure) as any break will cause problems. |
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The governor is hunting. Governors work by balancing spring force (opens throttle) against centrifugal force (closes throttle). If you installed the spring(s) incorrectly, this could be the cause. Could also be mixture issue. But most likely it is a spring issue. It never did this before. This all started around the end of summer last year. I had never taken it apart prior to that. Maybe the springs are wearing out? Or the linkage is getting gummy. But... I'd look at the gas supply first. Things to check: the carburator float is sticking the fuel line is partially blocked jet is plugged check that you don't have contaminated gas or gunk in your fuel tank if there's a fuel filter it may be clogged Fuel Filter is new....I'll try and check everything else you mention. Clean the carb really good and it will probably fix it, since it runs at full power. This is the plan....The weekend after next I will remove the carburetor again and soak it in cleaner. While it's soaking I will troubleshoot the fuel supply lines from the tank. |
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Briggs and Stratton carbs are pretty easy to work on, especially the single cylinder models. The bowls spin off, exposing the float and valve. The needles are Viton tipped, they are fine with ethanol gasoline. But the seats are brass which corrodes with ethanol. Use copper-dissolving bore cleaner, flushing with carb cleaner. The twin cylinder carbs are more complex due to parts count and linkage complexity. Both usually have a Mikuni fuel pump, check hoses (all three, suction, delivery and crankcase pressure) as any break will cause problems. Twin cylinder. I'll check all the hoses...thanks for the tip. |