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Good afternoon,

2nd post of the day to ask about a fuel system issue on a B&S 12hp on a Westwood T1200 ride on mower. The issue being the engine will start on the pull start, run with inconsistent revs for a time and then die. I believe this to be a fuel to air ratio problem, but I could be wrong. I have replaced the air filter, fuel pipe and fuel filter. Having removed the air filter and housing I have seen small amounts of fuel at the base of the filter. I have removed the carburetor and cleaned it, there was some rust at the bottom of the bowl likely due to age.
I have had trouble finding a replacement carburetor as they don't seem to be made in that shape anymore. I have attached an image of the model type and code as best as I could.

There plenty of after market 491031 carbs and even the OEM is available if you don't mind paying over $250.

jaylees150 said:

Good afternoon,

2nd post of the day to ask about a fuel system issue on a B&S 12hp on a Westwood T1200 ride on mower. The issue being the engine will start on the pull start, run with inconsistent revs for a time and then die. I believe this to be a fuel to air ratio problem, but I could be wrong. I have replaced the air filter, fuel pipe and fuel filter. Having removed the air filter and housing I have seen small amounts of fuel at the base of the filter. I have removed the carburetor and cleaned it, there was some rust at the bottom of the bowl likely due to age.
I have had trouble finding a replacement carburetor as they don't seem to be made in that shape anymore. I have attached an image of the model type and code as best as I could.

Click to expand...

Try removing the carburetor one more time and cleaning it again. Does it have a diaphragm that needs to be replaced? Did you remove all jets, etc. ? Did you use carburetor cleaner, a really thin wire, and a compressor blow gun to clean carburetor? Are the gaskets all in good shape and installed correctly? Does it have an air/fuel mixture screw adjustment? Are you running it with air filter on? Is air filter correct and in good shape?

Jonny, you say you are new to help forums so I’ve got a couple of suggestions which will help you out. You’ve made some mistakes (posting two threads about different engines, but not clearly identifying what is going on) so I suggest you start over, and follow these steps in both threads.
1. Do not mix any info between threads, each is a separate problem.
2. Post all engine numbers for the engine in that thread.
3. Post your questions as clear as possible, only for that engine.
4. With this info we should be able to help you out.
5. Make sure that you only ask about 1 engine in each post.
Hopefully you will start over using these suggestions, or it is highly unlikely we can help you out.

You need to adjust the fuel-air ratio with the screw on the bottom of the bowl. Turn it counterclockwise to richen the fuel mixture. Turn it until the engine smooths out and continue turning until it starts to run poorly. Then screw it inward until it begins to surge, then back it off to get it between a rich and lean mixture. Then bring the engine down to idle and adjust the screw on the top of the carb until it idles smoothly That carburetor is discontinued. The cheap Chinese knockoffs on Amazon rarely, if ever, run well no matter the reviews. One more thing to check is the throttle shaft bushing. See if you can move the throttle shaft fore and aft and side to side to see if it moves around. Be sure to hook up the little spring on the throttle linkage rod to the throttle itself.

Strip the OEM carb down. Separate metal from rubber and plastic parts. Boil the metal parts for 45 minutes. Cheap hot plate and pan. Blow out with carb cleaner and compressed air. Safety glasses should be worn. Carb cleaner burns the eyes, ask how I know. Might take several cleanings. Fuel tank needs to be in new condition. No rust or chunks of anything . Seal the tank like the motorcycle guys do if needed.

Last resort, Chinese carbs on Ebay for cheap. https://www.ebay.com/sch/i.html?_nkw=491031&_sacat=0&_from=R40&_trksid=p4432023.m570.l1313