B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot

sp80

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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot

My snapper with B&S 725ex, 190cc, L Head engine, made 03/2013 starts easily then runs rough until hot. After engine is warm it begins to smooth out gradually. Same symptoms since 1st start in 2013. Multiple spark plugs set at .020 made not appreciable difference. B&S 591868, champion RJ19LMC, 5861, and NGK BR2-LM no help. Snapper manual says .030, but B&S says .020 for that engine.
 

Rivets

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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

I’ll put my money on one of two things, but involving removing the carb. Either the float level is set too low or the jet is partially plugged. I would probably figure the float level is set too low, creating a lean mixture. Replacing the float needle and seat and setting the float level correctly should do the trick. Going a little further, as long as you have the carb off, giving a good cleaning, making sure the Jets are open wouldn’t take too much extra time. Here is a procedure I use for both.

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.

 
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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

Sp 80 do you have a Primer bulb on that engine or a Easy start with auto choke ?? I am familiar with those Briggs engines on Snappers... I'm betting on the auto choke with no bulb.....

Let us know Mon Ami ~!~!
 

sp80

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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

My snapper with B&S 725ex, 190cc, L Head engine, made 03/2013 starts easily then runs rough until hot. After engine is warm it begins to smooth out gradually. Same symptoms since 1st start in 2013. Multiple spark plugs set at .020 made not appreciable difference. B&S 591868, champion RJ19LMC, 5861, and NGK BR2-LM no help. Snapper manual says .030, but B&S says .020 for that engine.[/QUO
 

sp80

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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

Thanks

My engine has an auto choke. I also think the choke may be issue. My engine is an easy start model. B&S recommends BS 591868 with .020 gap but lists several spark plugs with .030 gap for all L Heads. I'd like to know why the discrepancy.
 

sp80

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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

Thanks for your response.
 

sp80

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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

Thanks

My engine has an auto choke. I also think the choke may be issue. My engine is an easy start model. B&S recommends BS 591868 with .020 gap but lists several spark plugs with .030 gap for all L Heads. I'd like to know why the discrepancy.
 
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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

Champion RJ 19 LM is the most common and comes on new L Head briggs and Gap at .30
 

ILENGINE

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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

Thanks

My engine has an auto choke. I also think the choke may be issue. My engine is an easy start model. B&S recommends BS 591868 with .020 gap but lists several spark plugs with .030 gap for all L Heads. I'd like to know why the discrepancy.

Briggs has a few engines both flat head and OHV that require the .020 gap or you risk misfires and hard starting at .030. The problem is the .020 gap plugs like to foul out without any rhyme or reason.
 

sp80

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  • / B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until hot
Re: B&S 725ex 190 cc made 3/2013. Engines starts 1st crank, misfires and surges until

Champion RJ 19 LM is the most common and comes on new L Head briggs and Gap at .30[/QUT

Thanks Mr.Boudreaux in Eunice. We are almost neighbors. I am experimenting with a NGK BR2-LM, but have not pushed the gap to .030. So far .020 seems to run oK after it's warmed up. I exchanged the original Snapper for this one. Both had identical problem. I think the auto-choke releases too fast causing a lean condition. It runs smoothly for about 2 minutes after starting, then surges and misfires until hot. After it warms up it runs smoothly.



the originial
 
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