Briggs & Stratton Series 650 needs constant priming to stay running

azsportpilot

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  • / Briggs & Stratton Series 650 needs constant priming to stay running
Hello all, new member here…
I just bought a used Swisher Trim-n-Mow (22") Walk-Behind String Trimmer
with a B&S series 650 motor

Or more specifically it’s a model 124T02-0129-E1

With a date code of 06121559 so I guess it’s about 12 years old

It was a non-running purchase but the price was right.

I started with a 5140B Tune up kit…. oil, spark plug, air filter (which was missing)

And of course a fresh tank of gas, but it would just sputter but not start, …. and it would only sputter after 4-5 shots of prime

Well I had a second person pull the cord while I continuously and briskly pumped the red primer plunger after it sputtered and I was able to keep it running for several minutes but as soon as I stopped priming, the engine would stall immediately.

So what do you think? I’m thinking a carburetor problem but what specifically?

I pulled the bowl and it was surprisingly clean, fuel flowed when the float dangled and stopped when lifted
 
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  • / Briggs & Stratton Series 650 needs constant priming to stay running
Ok I know that carb very well and can rebuild them blind folded....... When you took the bowl BOLT out that is your main jet.......

Take it out again and there is a hole on the top that meets the 2 holes on the sides of the bolt near the head of it pass a stripped bread tie in all three of those holes then spray with carb clean.....

Make sure those holes are clean and you see thru them... Put it back on and fire that puppy up ............

Let us know Mon Ami ~!~!
 
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  • / Briggs & Stratton Series 650 needs constant priming to stay running
A lot of people call that a bowl NUT we know it as that also ..........
 

azsportpilot

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  • / Briggs & Stratton Series 650 needs constant priming to stay running
I blew through it while i had it out, air passed through but i did not clean it well, just blew through it and figured since it was not blocked it must be ok

will try that tomorrow
 
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  • / Briggs & Stratton Series 650 needs constant priming to stay running
Like I said there is a hole on top of it..... If that is clogged no gas can be sucked up from the side holes up into the tube.....

Was there gas in the bowl when you took the bolt out ????
 

azsportpilot

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  • / Briggs & Stratton Series 650 needs constant priming to stay running
Like I said there is a hole on top of it..... If that is clogged no gas can be sucked up from the side holes up into the tube.....

Was there gas in the bowl when you took the bolt out ????

yes the bowl had fuel in it, when i starting loosening the bolt fuel started pouring out

once the bowl was removed i blew in the hole in the bolt and air came out 1 or 2 of the side holes
 
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  • / Briggs & Stratton Series 650 needs constant priming to stay running
Check that bowl nut again and clean it well..... If that don't do it then you need a carb kit and a complete tear down and a soaking in a carb bath........

Let us know Mon Ami ~!~!
 

One1

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  • / Briggs & Stratton Series 650 needs constant priming to stay running
Having the same issue. Will this engine run without the backpressure of the crank case vent? The air filter housing is in the way of everything I'm doing and I'd like to just get it running before putting everything back on. I know that vent feeds into the carb bowl and pressurizes it, but thought it may suck enough air in to run with the cover off (so vent hose, filter, and filter box casing removed from carb). Once it runs longer than 1 second I'll button it up.
 
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  • / Briggs & Stratton Series 650 needs constant priming to stay running
Having the same issue. Will this engine run without the backpressure of the crank case vent? The air filter housing is in the way of everything I'm doing and I'd like to just get it running before putting everything back on. I know that vent feeds into the carb bowl and pressurizes it, but thought it may suck enough air in to run with the cover off (so vent hose, filter, and filter box casing removed from carb). Once it runs longer than 1 second I'll button it up.

Yes it will run without the tube connected I do that all the time when I work on them...... You just might have a loose or broken intake tube..... The intake tube comes from the carb under the coil and 2 bolts hold it to the block..... Your O ring behind the carb may be an issue also ..........

If you have the air box still attatched that means you didn't take the carb off and clean it well.. Right ??
 

One1

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  • / Briggs & Stratton Series 650 needs constant priming to stay running
I was having idle issues running WITHOUT the airbox, but a second cleaning of the top hole in the main jet seems to have fixed it. Curiously however I didn't get the upper rpms i was looking for tuning until I force fed the carb bowl to simulate the vaccume it would get with the airbox on.

https://s31.postimg.cc/wl1l24dqz/20180426_180718.jpg

So thats how I solved that. No starvation of gas in the throat of the carb that way.
 
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