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Rebuilding A B&s Carb

carberator briggs & stratton

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#1 slufoot733 OFFLINE  


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Posted May 12, 2013 - 12:35 PM

I have resurrected a 1983 Montgomery Wards (MTD) lawn tractor and have it running, kinda. It has a 10hp B&S model 220707 engine with a #491026 carberator. It's been stored for 6 years and after a good cleaning it fired right up. But, the carb has a few issues. I can (and will) get a rebuild kit this week. But, the throttle plate shaft is very loose and bounces around too much. I know it's allowing excess air into the mix. A new carb costs $184.96 which is more than the tractor is worth. I recall seeing something about replacing the brass throttle shaft on B&S carbs with an oversize shaft but I cannot find any info on how to do this or where to get the proper parts. I know the shaft is slightly larger than the OEM. You have to ream out the bearing holes, then insert the shaft which fits just right. Anyone have any info on this? Any help would be greatly appreciated.



Edited by slufoot733, May 12, 2013 - 12:37 PM.

#2 glgrumpy OFFLINE  


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Posted May 12, 2013 - 02:24 PM

Haven't seen the shaft avail before. You're right, carbs are high on epay at least.  Make sure you remove the main jet tube after you remove the needle valve adjuster BEFORE separating carb halves. Important, so as not to bend it, and won't come apart easy Unless you DO that. Kits are pretty good and cheap. Biggest issue I have is they seem to be a leaky carb, even after cleaning. Just leak once in awhile, when it has a wish too I guess??  Won't leak constant, usually after stopping and parking.


  Bushing kits available on epay for Kohler carbs, some come with many inserts. Not sure you can make any of those work, but might check them out. Getting exact size drill bits may be biggest issue. Not sure if Briggs would have a lip to push them into or not. Might wanna fall in if not and not work. My .02 worth and just as valuable! :smilewink:

#3 boyscout862 OFFLINE  

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Posted May 12, 2013 - 02:47 PM

Have you looked at the manuals in the "MANUAL" section for your engine. B&S did a great job on their manuals. I would look for a carb off of another old engine.  Good Luck, Rick

#4 achomesteader OFFLINE  


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Posted May 12, 2013 - 03:08 PM

It's probably just the brass throttle shaft that is worn. Try a new one and see how it fits. If you should have to install new bushings, after pressing them in, check new throttle shaft for free movement. If shaft doesn't move freely, ream bushings out with 7/32" drill.

#5 LilysDad ONLINE  


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Posted May 12, 2013 - 06:06 PM

I would bet someone on here could make a new shaft for not too much trouble. Or a couple of bushings.....

#6 superaben OFFLINE  


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Posted May 12, 2013 - 06:28 PM

A couple points.  First, leaks are optional on the big Flo-Jets.  You can put a small o ring on the end of the jet where it seals at the inside of the carburetor passage.  I mean small, not a big fat one.  There's also a sealing washer you can use, too, but I prefer the o ring.  You will need to back out the adjustment needle to compensate, but it will seal.  I have done many that way without a problem. 


Second, a worn throttle shaft is not that big of a deal in all honesty on these carburetors.  I had one that I could see daylight through.  It did not idle well cold, but once it was warm (~5-10 minutes) it would idle as slow as I could get the mixture right.  All you will have to do is richen the mixture a little more than the manual will say to compensate for the extra air flow. 


You can still find a NOS throttle shaft, but it isn't cheap.  You can also sometimes find just the upper half.  However, my advice is don't fret about the throttle shaft.  If you soak the carburetor in a good cleaner, replace all the parts with a quality kit, and give it ethanol free clean fuel you will probably find that it isn't going to be a problem. 


Third, the biggest problem these carbs have is warping at the bowl sealing surfaces.  Check that with a straightedge. 


Fourth, be very careful of the threads at the jet.  They strip very easily.  I haven't done it, but I have a perfectly good FloJet carburetor with stripped threads that is waiting its turn to be repaired.  It takes a strange tap (5/16-32) to repair it.


Ben W.

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#7 Amigatec OFFLINE  


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Posted May 12, 2013 - 06:33 PM

I did have a throttle shaft break on a B&S carb once. It was kinda strange, it went to full throttle and there no way to slow it back down.

#8 slufoot733 OFFLINE  


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Posted May 14, 2013 - 09:17 AM

Thanks everyone for the info. Based on what I've read here, and elsewhere, I have ordered an overhaul kit for the carb. I also found a new throttle shaft online and ordered that. I will overhaul the carb with new needle valves, seals, gaskets, etc. As Greg mentioned, the brass shaft would wear before the other metal of the carb body so that's whay I got the new shaft. It should clean up most of the slop.

I was stunned that after six years of storgae (in a shed) this old critter fired right up. I did clean the carb with a good carb cleaner solvent and put fresh gas in the tank. All I needed was a battery. It runs fairly well but I expect much improvement after the overhaul.

Thanks again guys,


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