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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.

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.

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 ~!~!

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

sp80 said:

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

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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.

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

Thanks for your response.

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.

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

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

sp80 said:

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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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.

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

Boudreaux In Eunice La. said:

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

Where you at Sp 80 within 50 miles ??

IL engine is right on the 20 gap for the plugs.... When I get one IF I think about I do .25..........

Is your spring intact ??? Is your choke opening all the way about 30 seconds after starting ?? Is the plastic vane obstructed by a dirt dauber nest ???

I see that all the time under the air shrouds at my shop ~!~!

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

Boudreaux In Eunice La. said:

Where you at Sp 80 within 50 miles ??

IL engine is right on the 20 gap for the plugs.... When I get one IF I think about I do .25..........

Is your spring intact ??? Is your choke opening all the way about 30 seconds after starting ?? Is the plastic vane obstructed by a dirt dauber nest ???

I see that all the time under the air shrouds at my shop ~!~!

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The spring appears to be good. The vane is not obstructed and I haven't observed the choke after starting, however the engine starts easily and runs smoothly for about 30 seconds or a little more then runs roughly until warmed up. After warm up it smooths out. If I stop and restart it follows the same pattern.

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

Boudreaux In Eunice La. said:

Where you at Sp 80 within 50 miles ??

IL engine is right on the 20 gap for the plugs.... When I get one IF I think about I do .25..........

Is your spring intact ??? Is your choke opening all the way about 30 seconds after starting ?? Is the plastic vane obstructed by a dirt dauber nest ???

I see that all the time under the air shrouds at my shop ~!~!

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I am in Lafayette

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

sp80 said:

I am in Lafayette

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I think this may be a common problem with this model. I exchanged the first one for this one. Both had the same issue out of the box. Fortunately the engine does start and runs OK after it warms up. I am somewhat anal about a smooth running engine. Thanks for your responses.

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

ILENGINE said:

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.

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I tried .030 with the original plug and it didn't help. In fact I did get more misfires and surging. That was a Champion RJ19LMC /BS 591868 plug. The same model manufactured before 11/2011 used the .030 gap. I wonder what was changed in the engine.

Thanks.

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

sp80 said:

I tried .030 with the original plug and it didn't help. In fact I did get more misfires and surging. That was a Champion RJ19LMC /BS 591868 plug. The same model manufactured before 11/2011 used the .030 gap. I wonder what was changed in the engine.

Thanks.

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If I remember correctly it was due to a change in the ignition module to meet tier 3 emissions standards.

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

ILENGINE said:

If I remember correctly it was due to a change in the ignition module to meet tier 3 emissions standards.

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Thanks for that response.

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

Ok now that you got into detail about it , i'll bet you have the shiny carb on there. The later models of those engines do run rough then smooth out... Briggs found a new place to make their carbs ?? Not the good carbs like on the older ones.

I have changed a few of those already.... Thinking they were chinese carbs...... Those mowers have to be perfect to run smooth...

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

I don't know if they're still made, but Champion used to make spark plugs for two-cycle engines to deal with plug fouling. The ground electrode (if that's what it's called) only extended halfway across the center electrode. Maybe one of those plugs, with a split-the-difference gap of .025 would do the trick.

With that said, I don't think it's a spark plug problem. Sounds like a choke not opening fast enough.

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

cpurvis said:

I don't know if they're still made, but Champion used to make spark plugs for two-cycle engines to deal with plug fouling. The ground electrode (if that's what it's called) only extended halfway across the center electrode. Maybe one of those plugs, with a split-the-difference gap of .025 would do the trick.

With that said, I don't think it's a spark plug problem. Sounds like a choke not opening fast enough.

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I agree on a choke issue Purvis... I thought it was a auto choke system from the first post he put up... Hence the questions about spring and such..

Sp 80 take the cover off the air box and remove the filter.. .......... Then look at your choke... Note where it's at...

Then start the engine and keep a eye on the choke butterfly until a few minutes have passed.... It should be warmed up good in 3 minutes.....

Then report back to us what you see ...........

Plus Tard Mon Ami .......Oh I got a video on how that works.. I'll post it later ~!~!

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

Here's the video It's only 1 minute 27 sec but it shows the main things to look for, enjoy ~!~!

https://youtu.be/qOm-D93Y9-k

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

Boudreaux In Eunice La. said:

Ok now that you got into detail about it , i'll bet you have the shiny carb on there. The later models of those engines do run rough then smooth out... Briggs found a new place to make their carbs ?? Not the good carbs like on the older ones.

I have changed a few of those already.... Thinking they were chinese carbs...... Those mowers have to be perfect to run smooth...

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Speaking of chinese! i just purchased a B&S 591868 spark plug from Amazon, which is marked 591868 ON THE Package, but is stamped 992300C on the plug. It was pre-gaped at less than .020 and Package is marked made in china. I checked at home depot and the 591868 package contains the 992300c plug made in china also. I will report after trying that plug, however I am still working with the BR2-LM NKG.

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

Boudreaux In Eunice La. said:

I agree on a choke issue Purvis... I thought it was a auto choke system from the first post he put up... Hence the questions about spring and such..

Sp 80 take the cover off the air box and remove the filter.. .......... Then look at your choke... Note where it's at...

Then start the engine and keep a eye on the choke butterfly until a few minutes have passed.... It should be warmed up good in 3 minutes.....

Then report back to us what you see ...........

Plus Tard Mon Ami .......Oh I got a video on how that works.. I'll post it later ~!~!

Click to expand...

OK guys. I will run the engine and check the choke butterfly, then report back.

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

Boudreaux In Eunice La. said:

Here's the video It's only 1 minute 27 sec but it shows the main things to look for, enjoy ~!~!

https://youtu.be/qOm-D93Y9-k

Click to expand...

Watched it thanks.

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

sp80 said:

OK guys. I will run the engine and check the choke butterfly, then report back.

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I decided to try the low tech approach. I sprayed the choke, throttle springs and carb. with carb cleaner while running, through the hole in the air cleaner base plate. I added 1 once of Berryman- B12 chemtool fuel injector/carb cleaner to one gallon of gas and filled the lawn mower gas tank. I ran the lawn mower engine for 35 minutes. It ran rough for about 5 minutes then smoothed out. I shut down the engine. Today I checked the spark plug. It was normal(not Fouled.) I regapped NGK BR2-LM Plug to .025 from .020. Engine started first crank ran a little rough for about 5 minutes, then began to smooth out. It ran smoothly for 35 minutes on my driveway. Throttle handle was secured with a rope. I shut engine down and restarted. On restart it ran smoothly without the normal initial roughness and continued to run smoothly. This was the first time in 4 yrs. that it did not run roughly after restarting the engine once it had been shut down. I decided not to take the air cleaner plate off to check the choke, because I had not obtained a new gasket and I was afraid I might damage the gasket when I removed it. Since the plug was not fouled, and because it smoothed out after it warmed up I reasoned that the choke opened after warm up.

My thanks to Mr. Boudreaux and the other gentlemen who took the time to respond to my inquiry and offered helpful, detailed suggestions. You helped resolve my Snapper mystery. My machine runs better than it ever has.

Thanks to the Forum or providing this service.

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

Hey SP 80 don't go thanking me yet or anyone on this forum.... You FORGOT about Rivets in post # 2 when he shot you that info on the MAIN JET or as it's called a BOWL nut...........

I forgot about that being a issue..... It still can be an issue if it is not cleaned from the top hole down into the side holes...

That bowl nut or bolt as we call them is the main jet in the carb you have on that engine.... All 3 holes have to be cleaned well with a wire or tip cleaner and sprayed with carb cleaner well......

Also the air box has a filter that has to be put in place...... I also forgot about the O ring that the carb slips onto the intake tube....... Did you change that too ??

Ok Mon Ami Let us us know ~!~!

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

Thanks for the detailed information Rivets.

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

cpurvis said:

I don't know if they're still made, but Champion used to make spark plugs for two-cycle engines to deal with plug fouling. The ground electrode (if that's what it's called) only extended halfway across the center electrode. Maybe one of those plugs, with a split-the-difference gap of .025 would do the trick.

With that said, I don't think it's a spark plug problem. Sounds like a choke not opening fast enough.

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cpurvis : If you check a 2 cycle plug you'll see it only goes 1/2 way across the electrode, also some speed shop engine builders "cut" the plugs like that, thought was, it gave a broader spark in the cylinder.....

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

Boobala said:

cpurvis : If you check a 2 cycle plug you'll see it only goes 1/2 way across the electrode, also some speed shop engine builders "cut" the plugs like that, thought was, it gave a broader spark in the cylinder.....

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Thanks. I have several two cycle machines. I'll have to look closer at the plugs; I hadn't noticed. My memory of those plugs came from go-kart days many years ago.

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

Used to race McCulloch powered karts myself .... back in the 60s .. :thumbsup:
her's something you MIGHT enjoy .....

https://www.youtube.com/watch?v=apd1KBjLV8k

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

sp80 said:

Thanks for the detailed information Rivets.

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Did you check the bowl nut and that O ring I was talking about ???

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

I thoroughly enjoyed it! Far cry from my old Mac-6 and Mac-100 powered direct drive Karts. Most, if not all, of the Formula 1 drivers started on Karts.

The only time I ever drove on the street, I hit the high school principal's dog and rolled it right up into my lap. The dog wasn't hurt but the principal's wife saw it happen. He cut me ZERO slack while I was in high school. Can't say as I blame him.

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

Boudreaux In Eunice La. said:

Did you check the bowl nut and that O ring I was talking about ???

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I am going to run it like it is this week. If it starts to run badly, I'll get a carb kit and do a thorough clean out and gasket change. I cleaned the carb at the end of last season, but did not change gaskets and seals.

.

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

IF you decide to re-build your carb ..... here's a link that may be helpful !

http://outdoorpowerinfo.com/repairs/#id_briggs