Briggs motor missing

[mommicked]

My 07 24hp B&S Intek suddenly lost power like it was running out of gas. I shut it off, and checked-plenty of fuel. I restarted and it idles fine but shudders( goes Bugh,bugh bugh as it throttles up slower than normal and then backfires like every 2 secs. while at full throttle. No noticeable knocking. 121 hrs on engine. changed plugs,fuel filter and oil. Its better but still a miss or quiet backfire at full throttle. Any ideas on what to check? Im afraid it might be a valve issue?

 

[RogersJetboat454]

Re: Briggs motor missing

My 07 24hp B&S Intek suddenly lost power like it was running out of gas. I shut it off, and checked-plenty of fuel. I restarted and it idles fine but shudders( goes Bugh,bugh bugh as it throttles up slower than normal and then backfires like every 2 secs. while at full throttle. No noticeable knocking. 121 hrs on engine. changed plugs,fuel filter and oil. Its better but still a miss or quiet backfire at full throttle. Any ideas on what to check? Im afraid it might be a valve issue?

I assume the air filter was checked too? Owners manual give any indication on how may hours to adjust the valves at? Have you checked compression? Tested spark with a spark tester?

 

[windy5849]

Re: Briggs motor missing

Sounds like you may need a valve adjustment.Normally the clearances are .004-.006 on each valve adjusted cold.
Here is the Briggs adjustment procedure.The OHV section is near the very bottom and pay particular attention to the piston position when adjusting the clearance.Hope this helps.
http://www.briggsandstratton.com/engines/support/frequently-asked-questions/Servicing the valves/

 

[mommicked]

Re: Briggs motor missing

Than you both for your replies. Im gonna check the valves and compression. All the small engine places here are slammed tuning generators for Irene!!

 

[mommicked]

Re: Briggs motor missing

Ok now I feel dumb for asking for advice before doing more investigateing. When disconnecting the right side spark plug the engine continues to run smoothy at idle. the other instantly kills the motor. I have a spark but it doesnt look really hot and changed the new plug, same thing. so I ordered a magneto and plugwire (one unit), I noticed the bad side plugwire was bent back on itself under the shroud and smashed around the edge of a fin on the head. It looks like it might have been arcing there. I cant believe how smooth the motor runs at idle and wot,( except for slight audible miss), on one cylinder

 

[bigdee]

Re: Briggs motor missing

Sounds like MattMo sold you some of his gas!

 

[mommicked]

Re: Briggs motor missing

Update. I replaced the magneto and the motor ran weakly after pulling the good side plugwire. Still stumbleing and backfireing at throttle w both wires hooked up. I pulled off the valve cover on the bad side and found the intake pushrod laying in the head, the rocker pivot bolt had loosened enough to let it pop out, several complete turns!!. Pushrod looked fine so I reinstalled it, applied locktight to the bolt and gapped the clearance. It now runs flawlessly w no apparent damage, smoking,knocking etc. I have newfound respect for B&S engines toughness. But wonder a little about the assembler of my motor. loose rocker and loose exhaust pipe bolt on the same cylinder.

 

[john3931]

Re: Briggs motor missing

Could be a blown head gasket or valve seat popped out on one side. Did you have any grass build up or mouse nest under the blower housing when you took it off? I would do a leak down test on the cylinders.

 

[mommicked]

Re: Briggs motor missing

It now runs quieter and smoother than ever before. I think the rocker was loose from the factory. starting last spring it would not turnover w/o double bumping the starter. I replaced the battery last spring, it tested weak, but the new one had the same problem turning the motor so I assumed my starter was going bad. Now I know it was due to the intake valve not or barely opening so the compression wouldnt let the starter turnover easily. Now it turnsover and cranks instantly and runs smooth. I think Ive put 30+ hrs on it on one cylinder. I guess the 24hp had about 12 hp, enough to run the mower and cut the grass while some idiot tried to blow it up!!!! I dont see any signs of leakage at the head gasket and it had gobs of power cutting the to tall grass yesterday.

 

[RogersJetboat454]

Re: Briggs motor missing

But wonder a little about the assembler of my motor. loose rocker and loose exhaust pipe bolt on the same cylinder.

The new guy? Built over a weekend/holiday? On the job imbibing?

Well in any case sounds like you got it all squared away.

 

[Icyharp]

Re: Briggs motor missing

I had to laugh, lastnight my 18hp briggs started doing the same thing. So now I get to do the same thing, I know it is not fuel related, spent over an hour checking that, after I checked the filters, oil, changed plug......I was searching the same fix and know what I have to do, glad it is going good for you again, hope mine is fairly simple, should be as I have great compression and did not have any blockage in the cooling fins.

 

[mommicked]

Re: Briggs motor missing

I almost took it to a pro when it broke down, I was sure there was internal damage, bent broke valve or seat or something because of the backfireing. Funds and the local shops being too busy w Irene helped me save a couple hundred in repair cost by fixing it myself I'm guessing.I found the other Intake valve lash way too loose also, but both exhaust valves were in spec. after 125 hrs.

 

[j_martin]

Re: Briggs motor missing

Who in the world would steal a Briggs.

 

[guy74]

Re: Briggs motor missing

I have had valve train problems on every OHV briggs on the place, mostly the rocker studs backing out, or the intake pushrod failing. I now remove and locktight the rocker studs back in when they are new, I'll have to see how the 3 that have been bought this year and done that way last. Any of the one's I've had to fix have never repeated the failure.

 

[mommicked]

Re: Briggs motor missing

The rocker bolt that loosened on my motor appeared to have a small 1/8" ring of thread locker just under the pedestal the rocker sits on or barely into the heads threads the rest of the threads were clean. The other rocker bolts were tight as I tried more than a little to break them free and they wouldnt budge. All of the exhaust tube flange bolts were also very tight, except for the one on the loose rocker/bad magneto side. Could a weak spark on that side have caused the bolts to come out? sounds absurd to me. Also the fuel line slipped off my 1st mower because the line wasnot threaded through a hose holder cast into the fuel tank when assembled. That allowed the longish hose to dangle and shake itself loose from the tanks nipple. I returned and exchanged it after 2 mo. because the fuel leaked all over my deck and conc. shed floor, that should be another post) I guess the moral of the story is to go over a new mower looking for loose fasteners. It was a well know brand. and I expected better and let them know at the time of the gas fiasco.

 

[waterinthefuel]

Re: Briggs motor missing

I do a facepalm for people who start throwing parts at an engine before thoroughly investigating everything. From the onset, I could tell you something was amiss with the valves. That should have been the first thing checked. You always pull off as much as you can before replacing anything. If you aren't sure what the problem is, it can get very expensive to start throwing parts at an engine in hopes to find the right one.

I will say your issue is not one I'd ever heard of, but it did sound like something was wrong with the valves, I would have guessed the gap. But that would require you to pull of the valve cover which would have revealed the problem right at the beginning. You wouldn't have spent so much money replacing perfectly usable parts. If you can't return what you bought, just keep the old as a "spare." No reason to throw out perfectly good parts.

Live an learn I guess. I'm glad that everyone reading this can make a mental note "If my engine ever does this, I'll know where to look first." The benefits of a public forum like this can be great.

 

[mommicked]

Re: Briggs motor missing

The magneto must have been bad also because the motor would still run weakly when I pulled the other cylinders pwire after installing the new one. It instantly died when pullin the the good side wire loose w the old magneto. I only changed one magneto. Im still baffled how it could run wo the intake valve opening?.

 

[Icyharp]

Re: Briggs motor missing

Well not so good on my end yet, no money spent either, YET. So far I have adjusted the valves, ran better but not right and still gets hot. Although I will back up a tad, when adjusting the valves I adjusted the exhaust valve first then rotated the engine to do the intake. What I noticed was that I have vey little movement in the exhaust valve, I mean it is too the point that it is hard to see the rocker even move. So at this point I have come to the conclusion that my cam is shot. I called up my friends shop and he has a cam for 20.00 and gaskets for 7.00 bucks. I will be picking these up when I know for sure it is the cam.

What I do know at this point, compression was 150psi, the push rods are not bent, and the studs are still stuck in the head. No blown head gasket and piston and valves look fine. So I will more than likely be replacing the cam and lapping the valves upon reassembly. So far I have invested a little bit of my time and 1 beer.

 

[Tim Frank]

Re: Briggs motor missing

I do a facepalm for people who start throwing parts at an engine before thoroughly investigating everything. From the onset, I could tell you something was amiss with the valves. That should have been the first thing checked. You always pull off as much as you can before replacing anything. If you aren't sure what the problem is, it can get very expensive to start throwing parts at an engine in hopes to find the right one.

I will say your issue is not one I'd ever heard of, but it did sound like something was wrong with the valves, I would have guessed the gap. But that would require you to pull of the valve cover which would have revealed the problem right at the beginning. You wouldn't have spent so much money replacing perfectly usable parts. If you can't return what you bought, just keep the old as a "spare." No reason to throw out perfectly good parts.

Live an learn I guess. I'm glad that everyone reading this can make a mental note "If my engine ever does this, I'll know where to look first." The benefits of a public forum like this can be great.

I do a matching "facepalm" for people who apparently did read a thread but seemingly have ended up with no comprehension of what has been discussed and has transpired.
Even worse are the "I knew what the problem was all along and could have said so" gang. :facepalm:

OP was heading for the valves but while doing a visual inspection (the most important and what should be the FIRST step in any troubleshooting sequence) found a component that in his opinion should be changed out....so he did.
He then quickly got to the next problem, sorted it out, and is back in business.
Sounds pretty reasonable to me.

Criticising this after the fact, says far more about your diagnostic ability than the OP's.

 

[mommicked]

Re: Briggs motor missing

Thank you Timfrank, I think I did exactly what was recommended. The oil and plugs needed changeing anyway. My mower has that stupid safety ignition switch you have to reverse the key to mow backwards or it will cut the spark, usually at wot, and then returns it when you instinctively release reverse w the auto. trans. I would like to disable it because it cannot be good for the motor or the plugs to take the spark and then bring it back in a second or so w unburned/excess gas in the cylinders. I almost always forget to turn the key back. I just chewed up all the leaves and some small branches from Irene that covered the yard. Mower is way easier and faster than raking them. The mower seems to be running very well and Ive noticed the exhaust is not as strong smelling as before.