Briggs & Stratton Series 650 needs constant priming to stay running

Rivets

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  • / Briggs & Stratton Series 650 needs constant priming to stay running
I’m willing to bet that your float level is too low, caused by a float seat which is swelled during storage with old fuel in the system. I see this problem almost every day. My solution is to clean and rebuild the carb, with Briggs part number 398188. Here is the procedure I use.

Needle and seat replacement.


Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.


I would either give the carb a good 24 hour soaking or have it ultrasonically cleaned at this time.


With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. Next check to make sure that the float does not have any liquid in it. If it does, replace. If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.


PS: On the side of some Tecumseh carbs you will find a plastic cover. Under this cover will be an idle jet. Remove it and check to see that the jet is open both horizontally and vertically. You should be able to push the old float needle wire through the vertical opening.

 

azsportpilot

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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 ~!~!

Original Poster here....

sorry it took a while, well this morning i went out and fired it up, still had to continuously pump the red primer bulb to keep it running

next i pulled the carb and and cleaned with carb cleaner paying special attention to the 3 holes in the bowl bolt (main jet) i used the wire from a bread tie to clear the holes and sprayed em again

reassembled and it started on the first pull and stayed running without prime, but....

the RPM's sound a bit low, sounds like it is about mid throttle for a Briggs, furthermore it was surging a bit

i could see the black plastic thing on the top of carb (choke control?) moving back and forth with the surges

when i put my finger on the black plastic thing preventing it from moving the surging stopped

any idea how to stop that and to ensure full power is available?

thanks
 
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  • / Briggs & Stratton Series 650 needs constant priming to stay running
No choke on that one... You have primer that takes the place of a choke.... Your carb is still dirty or you have unmetered air getting in somewhere. Intake tube leaking at block... Or the o ring behind the carb is bad or missing....

Did you take the carb off ??
 

bertsmobile1

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  • / Briggs & Stratton Series 650 needs constant priming to stay running
Original Poster here....

sorry it took a while, well this morning i went out and fired it up, still had to continuously pump the red primer bulb to keep it running

next i pulled the carb and and cleaned with carb cleaner paying special attention to the 3 holes in the bowl bolt (main jet) i used the wire from a bread tie to clear the holes and sprayed em again

reassembled and it started on the first pull and stayed running without prime, but....

the RPM's sound a bit low, sounds like it is about mid throttle for a Briggs, furthermore it was surging a bit

i could see the black plastic thing on the top of carb (choke control?) moving back and forth with the surges

when i put my finger on the black plastic thing preventing it from moving the surging stopped

any idea how to stop that and to ensure full power is available?

thanks

Yes,
Clean the carb as in the previous post by Rivets and replace the needle & seat.
 

azsportpilot

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  • / Briggs & Stratton Series 650 needs constant priming to stay running
No choke on that one... You have primer that takes the place of a choke.... Your carb is still dirty or you have unmetered air getting in somewhere. Intake tube leaking at block... Or the o ring behind the carb is bad or missing....

Did you take the carb off ??

Yes I had the card off when i cleaned it at the workbench, I re-cleaned the main jet bolt and made the mounting bolts snugger and it seems to run ok now, ran a full tank of gas through it

thanks to everyone for all the help
 
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