20 hp B/S opposed twin surging

   / 20 hp B/S opposed twin surging #11  
As all above have said are things to look at. Also look at if it has a windvane type governer. Get a can of carb cleaner and spray all of the linkages. First blow or brush off any debris from the linkage. If you are spraying carb cleaner while it is running and you get it to start acting up look for gasket leaks between the carb and intake port.
 
   / 20 hp B/S opposed twin surging #12  
I have a 20HP B+S engine. Started surging and idling poorly. The problem with these carbs is they are low emission models and only the idle speed is adjustable,


, there ae no idle jets presa. The idle system is emulsion tubes, which you can Google, it is a system used on many modern small motors. You can clean and rebuild the carb, kits maybe expensive and the process is time consuming. A new B+S carb will list for $200.00 or more. This series of carbs are all Chinese produced, you can get a new one off eBay for about $32.00, identical to the B+S as it is is built in China. I don't believe in supporting the commies, but US manufacturers leave us no choice.

RN
 
   / 20 hp B/S opposed twin surging #13  
99% chance it is the carb. as I trouble shot mine from the ignition, compression , valves etc. This is a emission type engine which uses emulsion tubes for low speed idle and running. The idle speed is the only adjustment on the carb.
, you can get a rebuild kit, but the process takes over an hour. Look at the B+S engine model # as apparently there are 4 versions of the carb and each engine model. The carbs were all of Chinese manufacture. With the carb and engine model go to E bay and check out the models. You can get a new one for $31.00 to $34.00, select a USA distributor with product held and shipped free in the USA. Google emulsion tube as it is an interesting subject and theory. Both the B+S 20 and 24HP use the same carb for many years. My engine model is a 44R677 using a 796227 carb, manual choke.

Subby
 
   / 20 hp B/S opposed twin surging #14  
Unless you are buying marine fuel expect to have issues with carburetor suffered same issue on BS 20 HP twin on a woods mower- found ethanol in the fuel white rusted my carb bowl plugging jets. Short story rebuilt carb after soaking carb cleaner. Never buy any fuel unless it痴 marine fuel, no ethanol in it. Frustrating manufacturing does not coat parts to handle the ethanol better.
 
   / 20 hp B/S opposed twin surging #15  
Ethanol can be a ,some marine diesel filters will remove it along with the water. We had a 42 ft. research boat with a huge 6 cyl. Cat diesel and it had a filter with an element which could be drained, which spun the fuel through the filter, it be to large for use on a 20HP. I put an automotive filter on my tractor which can taken apart and cleaned, I also use a cleaning additive in the gas. I have yet to see a fuel injected small engine. Imagine potential repair cost? The B+S replacement carb (Chinese) lists for $200.00 to $249.00.!!

Subbie
 
   / 20 hp B/S opposed twin surging #16  
Small engine Fuel injection ? I think it's been going on for longer than people think. I have one on my Simplicity as a 24hp version. Says right on it... Fuel Injection...

Anyway, here's a link to a Kawasaki version of Fuel injection on a series of engines they are making.
EFI | Kawasaki - Lawn Mower Engines - Small Engines

Steve
 
   / 20 hp B/S opposed twin surging #17  
Changed the carb out with a new one. Eliminated surging

Subbie problem and it is running smooth. It took about 2hours off and on, as the top and side plastic engine shroud had to come off and the carb air intake. You will need a 4mm socket to dismount the carb from it's mount. The intake manifold bolts have to removed as the carb comes off as a unit.
 
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