# B&S 3.5 HP Throttleless Engine Problem



## billy3p (Jun 12, 2009)

I am sure this is redundant but I need to determine how to remove the carburetor on this engine to make sure there is no obstruction or varnish build-up that could be causing the engine to run very rough. I have replaced the plug but no help there. The mower was running perfectly last time in use but began lugging down like there was no gas left in the tank but when I checked there was. Should someone who has removed,cleaned and reinstalled a carb on this engine not mind speaking by phone please send me a contact number and I will gladly call. I am located in Dallas, Texas on Central Standard Time. Really need to get this running because the grass is going gangbusters with the recent rain.

Thanks,

Billy3p


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## 30yearTech (Sep 14, 2006)

Model number would be a big help, but since you stated it's a 3.5 hp Briggs, most likely has a diaphragm type carburetor mounted directly to the fuel tank.

These carburetors have a tendency for the diaphragm to distort and leak, a new diaphragm is most likely in order to make the engine run correctly.

Post your model and type number and Geo will likely post detailed instructions that will help with your issue.

Best of Luck.... :thumbsup:


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## geogrubb (Jul 28, 2006)

Briggs Carb
You need to install a new diaphram kit, it is Briggs part # 795083 or old # 495770 also Lowe's has a kit #5083 which has the same parts.

Here we go;
Remove air cleaner, there are 2 bolts that hold things together, one on the front of the tank 3/8" and one into the block 1/2", remove these bolts, now "slowly" slide the carb/tank off the intake tube and breather tube, now tilt the tank in to release the throttle linkage and waalaa the carb/tank is removed. Check the intake tube to see if the “O” ring seal and plastic retainer are still on the intake tube, if so remove them and re-install them into the carb. Remove the 5 screws from the carb/tank remove carb(don't loose the spring) now spray all holes, cracks and crevases in both the carb and tank surface with brake parts cleaner, remove the main screen(looks like a thimble) with a small screwdriver pry out the main jet(carefully) and clean it, reinstall the jet, it can be difficult some times to get it to snap back in place(I use the rounded end of a screwdriver handle). Remove and clean the fuel pickup stem. Clean any junk/rust from the tank. Install the diaphram on the tank then the gasket(no goo or sealer) now carefully replace the carb(the spring will try to misalign the diaphram), tighten all screws a little at a time so as not to crimp the diaphram until they are all tight. Install the carb/tank in reverse order and you are done. If I missed something one of the real mechanics will correct me. Have a good one. Geo


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## billy3p (Jun 12, 2009)

*B&S 3.5 HP throttle free engine*

Thanks for the reply guys. I had read geogrub's post about this to someone with a MTD mower but it sounded like his had a throttle control whereas mine is controlled strictly by a governor. can I ask to be sure that the instructions posted by geogrub will apply to the throttle free engine I have?

thanks,

billy3p


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## billy3p (Jun 12, 2009)

One other important thing,
Sorry for mispelling goegrubb's name.

billy3p


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## jack13man (Apr 28, 2008)

Yes this will still apply to your carb. Hope you get it going!


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## billy3p (Jun 12, 2009)

*3.5 hp B&S Throttle-Free Carb*

If anyone is online, I am in the middle of working on my carb and am trying to get the main screen off so I can remove and clean the jet. Geogrubb recommends using a small screwdriver to get the screen off. I am asking if the screen slides down off of the shaft or do you open the folds of the bottom of the screen to access the main jet? Also, does the screen on the bottom of the fuel pick-up tube come off(perhaps pry out using a knife blade tip?) and should I be able to remove the pick-up tube itself from where the tube goes into the bottom of the carb by pulling down on it or is it formed permanently to the base of the carb?
I really do not mind calling someone directly to discuss this while I have the carb in my hand if they are comfortable allowing me to call or if someone has free phone minutes and will call me that is fine too. I am at 214-774-2533 and am on CST in Dallas.

Thanks,
billy3p 
Billy


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## geogrubb (Jul 28, 2006)

The screwdriver is to remove the jet, screen just slides off, it really isn't necessary to remove the pickup tube if the tank wasn't really junky, just blow it out with carb or brake parts cleaner. Refer to the pics below for what it should look like. Have a good one. Geo


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## billy3p (Jun 12, 2009)

Thanks for taking the time to teach a neophyte Geo. I had talked with 30yeartech and he described exactly what you said and have shown. I wanted to make sure the screen did slide off as the picture shows. I think I will try to redo this from start to finish taking pictures along the way so I can hopefully help someone else should they need it. Visual always helps me tremendously. Hope you fared well in the rains that came through recently.

billy


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## 30yearTech (Sep 14, 2006)

billy3p said:


> Thanks for taking the time to teach a neophyte Geo. I had talked with 30yeartech and he described exactly what you said and have shown. I wanted to make sure the screen did slide off as the picture shows. I think I will try to redo this from start to finish taking pictures along the way so I can hopefully help someone else should they need it. Visual always helps me tremendously. Hope you fared well in the rains that came through recently.
> 
> billy


enjoyed talking with you today, was cleaning up after a job when you called, it was about 97 degrees and the humidity was off the chart. Post your questions about your weed trimmer and I am sure we can all help you with that as well.

:thumbsup::thumbsup::thumbsup:


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## geogrubb (Jul 28, 2006)

We are here to help, sometimes, as with my post for your problem, punctuation can change the meaning of something, which means I need to improve my wording of a solution to a common problem. However, did it fix it? Have a good one. Geo


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## billy3p (Jun 12, 2009)

*billy3p*

A big thanks to geogrubb,30yeartech and others in helping me get this mower back in service. down for a few days with a stomach bug but mowed today. Now if I can get the weedeater featherlite plus gas trimmer to run again I will be a happy camper. I have yet to find a model number anywhere. Can only find the engine serial number and class which I have posted in the 2 cycle engine forum with my problem.

Thanks again,

billy3p


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