# Need some expert help on a B&S carburator



## justin3 (Apr 10, 2007)

Engine Model 28B702, type 1154-E1, year 2000

I had to replace a carb on a snapper 9hp Rear engine rider, I replaced it with a used identical carb from a local dealer, before installing I rebuilt it and installed the proper main jet for my 9hp engine. When the engine runs at high speed it hunts, unless (here is my confusion  you loosen the little jet on the top of the carb off to the side 1/4 of a turn. Then this baby runs perfect. I noticed that the original carb didn't have this little jet, just a metal ball in place. Unfortunatly I can't leave the jet like that because its designed to be screwed in all the way. 

Anyone have any ideas on why this would be happening?


-Justin:thumbsup:


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## pyro_maniac69 (Aug 12, 2007)

are you talking the jet on the throttle side of the carb, sticking out at an angle towards you? if so, that is actually a high-speed mixture adjustment, if you screw it out a little bit and it runs better, leave it like that, if your afraid that it is going to fall out, see if you can find a small spring like you would on a little 2-cycle carb, and put that on the jet so it will keep tension on it, and prevent it from falling out


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## 30yearTech (Sep 14, 2006)

Do you know the model type and code number off the engine that the carburetor came from?

That may be an air bleed adjustment (its not the high speed adjustment, thats fixed and not adjustable). If its actually an ajdustment screw then it can be left that way. If its just a cover then the air bleed port is restricted and you need to go back in and make sure everything is open.


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## justin3 (Apr 10, 2007)

Unfortunalty I do not know the model, type or code from the engine the carb came from, i just pulled it out of a pile of carbs from various engines .
Heres a picture of what I am talking about, if I unscrew it 1/4 out the motor runs fine, i figure it was just something clogged but with alot of money invested into this mower I wanted to ask first since I only have had experiance rebuilding 3 of these. 








I will let you guys know the results tomorrow after a cleaning, hopefuly the new needle and seat kept my fuel in the carb and not all over my drive way tomorrow :freak:

Oh and heres the reason I replaced the carb, just for kicks :wave:









Thanks


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## geogrubb (Jul 28, 2006)

I just fought what seems to be a similar problem with the same carb on a Snapper 8hp, I cleaned the carb twice and it still surged so I chased it down to an air leak between the carb and intake so I put some silicon on the old gasket and let it cure, when I put the carb on and tightened the bolts the ear on the intake snapped off, it had been cracked right into the air passage, if it hadn't snapped off I would still be chasing it. So check the intake for a crack. Have a good one. Geo


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## justin3 (Apr 10, 2007)

Thanks for the reply Geo, I checked for any cracks and their were none, im using all new gaskets and i also checked for leaks but found none. It still won't run right with the air bleed screw tightened down, if I open it 1/4 a turn, it closes the passageway and the motor runs like its new, i've got the feeling that pilot jet (as briggs calls it) isn't for this motor and thats whats causing my problem, anyone got any idea?


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## pyro_maniac69 (Aug 12, 2007)

ok, my suggestion won't work, that screw needs to stay in all the way all the time

and those carbs aren't exactly the same, I wonder if the newer one isn't the right one for that motor, and it isn't supplying enough fuel for the motor to run coreectly


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## justin3 (Apr 10, 2007)

Yeah Pyro thats what I think the problem is, but i hope not because i don't have another carb for it. Tomorrow however I will be going over my friends house and he has a 10hp engine on his toro that is the same series as my 9hp. I will check his pilot jet and compare it to mine, I have the feeling that is the problem but i dont really know for sure yet.


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## 30yearTech (Sep 14, 2006)

You might want to try a different main jet. This carburetor may have a bigger or smaller bore then the original and may require a different jet. Sometimes manufacturers make 2 or 3 different HP rated engines based on the same engine and just use a different carburetor that has a small, medium, and large bore with a larger corresponding main jet. Perhaps this carburetor came off of a higher or lower hp unit and needs the correct jet in it. 

Just a thought, I know Kawasaki does this. I am not sure about Briggs.


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## justin3 (Apr 10, 2007)

Thanks 30year, and your right Briggs does do this for a fact, though the bore size was the same on the old and replacement carburetor i can assure u that. I ordered and installed the jet specificly for my engine, I do however have the other jets as well and I will try a bigger on out if worst comes to worse.

On the other hand I have a queston, when you install the jet are you suppost to clean the paint off it that briggs uses to identify it? I removed my main jet and found some paint particles in the passageway :0 maybe that was my problem. I am also gunna remove the welch plug and change that. Ill let you know the results


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## 30yearTech (Sep 14, 2006)

You know justin, thats a good question! I have never given it a second thought, I always leave the paint on and just install it. I have never had any problems, but I have noticed that there is never any paint on them when I take a carburetor down.


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## justin3 (Apr 10, 2007)

I think the paint disolves with the gasoline over time, but i cleaned it all out just to be sure. I also took your advice and tried the next jet up which has an extra hole in the top, no difference in engine performance. I got the engine to run smoothly at one point by opening the high speed adjustment all the way, but when i went to idle and back to high speed it started hunting again. Im starting to think this carb came off either a toro or an ariens because thats all the dealer services normaly...It may possibly have been on an 8hp and requires the smaller jet which has holes located in diffrent places, maybe one feed the piot jet. Will try the smaller jet tomorrow.

EDIT: heres the carburetor numbers if that helps LMT 5-4993 Walbro 30


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## justin3 (Apr 10, 2007)

Ok well even though its too late to install the carburator and try it out, I believe I found my problem. I went over to my friends house and he had the old carburator to his toro which constantly leaked gas. I took out his high adjustment screw and noticed a difference between mine and his. If you can see the photo below you will notice the black one from my friends carb has a shorter needle then mine.








With the shorter needle it would need fewer turns to open up the hole, with the longer needle it would take more turns and this explains why my engine would begin to run better when the high speed adjustment was turned out a ways almost falling out. So this carb must be an older one and require the older screw, while the original carb was a 2000 model and had all that EPA crap. Ill try it out tomorrow.


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