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post #16 of 27 Old 08-05-2019, 12:34 PM Thread Starter
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Re: Briggs 28N707 15HP Died and Won't Start

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Originally Posted by hazyadaze View Post
It certainly looks like a timing or valve issue. How does the governor arm feel? Is it floppy or does it have limits?
The governor arm feels alright, but my only frame of reference is this tractor, so I'm not sure if it's good. When I rebuilt the engine the governor was in one piece, and I know it was reinstalled correctly as it ran fine for several weeks. Of course it could have easily exploded since then hah... could you enlighten me on how the governor would be affecting it? I have a vague understanding of how it works but not enough to trouble shoot it. What should I be looking for?

b440- This carb has no solenoid, it's just a screw. It's a copy of the old Walbros

38racing- I can get it to fire as is, after adjusting the valves to .03 intake and .05 exhaust, but it will chug and die immediately. The manual calls for .05 intake and .09 exhaust, but the briggs chart online gives a wider range so I went with that.

Should I try adjusting the intake valve down tighter? Any harm in getting either or both of them super tight? Im clearly shooting in the dark here so I dont want to make things worse

The cam was OK when I rebuilt the engine, and I recall it having the little spring loaded decompression release. Seemed OK. I imagine that's hard to kill but I could be wrong.
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post #17 of 27 Old 08-05-2019, 01:02 PM
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Re: Briggs 28N707 15HP Died and Won't Start

I don't know that the governor could or would affect it like that. Just trying to think of easy stuff first.
Disconnect the arm from the carb and make sure it swings a little bit. You can tell if it exploded because it will have big wide floppy swings as compared to the short tight swings it has when it's good.

Have you done the wet test or a leak down test?
Have you checked your pushrods for straightness?
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post #18 of 27 Old 08-05-2019, 06:40 PM
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Re: Briggs 28N707 15HP Died and Won't Start

When listening to the video appears you need to take a closer look at your valve train and re-look at post #8 by TobyU.

You got a promise by setting the valve lash to less than minimum specs and got a almost run. this is a hint.



Make sure both rocker studs are tight. (They can come loose)

Adjust the valves per the service manual.
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post #19 of 27 Old 08-05-2019, 10:13 PM
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Re: Briggs 28N707 15HP Died and Won't Start

Pull the valve cover. Sound like a rocker arm stud is loose or a bent pushrod.

The intake (bottom one) is .003-.005 and exhaust (top one) is .005-.007.
Have to set at 1/2 inch past TDC of compression stroke.
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post #20 of 27 Old 08-05-2019, 11:47 PM
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Re: Briggs 28N707 15HP Died and Won't Start

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Originally Posted by TobyU View Post
Pull the valve cover. Sound like a rocker arm stud is loose or a bent pushrod.

The intake (bottom one) is .003-.005 and exhaust (top one) is .005-.007.
Have to set at 1/2 inch past TDC of compression stroke.
Wondering what manual OP was quoting in post 16 that said valves were 5 an 9. That would be more like those of a L head.
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post #21 of 27 Old 08-05-2019, 11:53 PM
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Re: Briggs 28N707 15HP Died and Won't Start

If the governor failed I would expect the engine would run at very high rpm assuming governor (throttle spring) is still attach. Throttle lever would pull throttle plate wide open. Now if governor spring were off and governor is working then it should run at idle, assuming idle screw is not set for too slow a speed.
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post #22 of 27 Old 08-06-2019, 12:02 AM
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Re: Briggs 28N707 15HP Died and Won't Start

I've seen those pushrods wear at the point they rub on guide. I reverse them when changing head gasket. One lady's blew head gasket and bent rod. Not sure which happened first. Nor sure if that 28 series had the valve guide moving issue or its just the 31s. Haven't actually had one of those yet.
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post #23 of 27 Old 08-06-2019, 12:46 AM
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Re: Briggs 28N707 15HP Died and Won't Start

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Originally Posted by 38racing View Post
I've seen those pushrods wear at the point they rub on guide. I reverse them when changing head gasket. One lady's blew head gasket and bent rod. Not sure which happened first. Nor sure if that 28 series had the valve guide moving issue or its just the 31s. Haven't actually had one of those yet.
Yep. Always flip at least the aluminum pushrod which is on the intake on the 31 and 33 series but some are different.
I have seen 3 pushrods wear completely in two pieces from rubbing on the guide. I don't know how plastic can wear through aluminum but seen it 3 times.

Head gaskets won't cause a bent pushrod but I guess a backfire could or hydro-locked situation could too.
Usually, a rocker arm stud (usually exhaust) loosens up and then when it is trying to expel the exhaust and can't and the pressure is still high in the cylinder and the intake is trying to open for when the piston goes down in second....the pressure is keeping the valve shut harder than it should and the aluminum rod bends.
In the case of slipped valve guides, the mechanical contact and lack of enough room to move causes the bend or rips the rocker in half like one last week did on the steel exhaust pushrod.
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post #24 of 27 Old 08-07-2019, 11:02 AM
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Re: Briggs 28N707 15HP Died and Won't Start

Change the spark plug, Pull the flywheel and check the key, Pull the head, as you stated a seat had come loose, could be a bad head gasket, or valve adjustment . A compression test would help, and a leak down tester would be of better help .

You don't have a plugged fuel line do you ???? Or no fuel ???

My 2 cents , Jim
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post #25 of 27 Old 08-07-2019, 11:06 AM
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Re: Briggs 28N707 15HP Died and Won't Start

Does this engine have the nylon cam shaft ?
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post #26 of 27 Old 08-07-2019, 11:23 AM
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Re: Briggs 28N707 15HP Died and Won't Start

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Hey all,

Learned quite a bit on here over the years but finally ran into an issue other threads couldn't solve. Here's what I've got going on, any ideas or help would be appreciated!

Craftsman LT4000 with a Briggs I/C Gold 15HP motor. Got it off of craiglist for $75 (it ran great last year! hah...) and found out it had thrown a rod and a valve seat had come loose. Fixed 'er up and for $150 all in I had a decent riding mower, which is way cheaper than a running ones go for in my area - $400 or more.

Now to the issues...The other day I was mowing when I happened to go over a big 'tuft' of grass- not a stump or root, just a big tuft of fescue. The mower bogged down, threw a small puff of smoke, and quit running. It still refuses to run after a week of troubleshooting.

I have good spark for sure. I also have fuel, because the plug is wet when taken out and smells of gas. I've cleaned the carb multiple times to make sure that isn't an issue as well.
I'm also positive the valves are within spec, as I've checked them three times. Valves aren't stuck as best I can tell and seem to move freely. There is compression but how much I dont know as I don't have a gauge... but it feels good to my novice hands.
Lastly, the flywheel key looks good and isn't sheared. I didn't take the whole flywheel off but I took the cover/bolt off and looked directly at the keyway- everything is lined up and intact.

Any ideas what else I could check out? I'm kind of stumped and the grass is only getting longer hah!
Sounds like you STILL have rod-valve issue. When you have any descent compression, gas, and spark it will still try to run but rod-valve problem you started with has returned.
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post #27 of 27 Old 08-08-2019, 05:04 PM
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Re: Briggs 28N707 15HP Died and Won't Start

Fuel, fire , air under pressure. Aint it great. Its that simple,sometimes. Piston/valves create pressure. Spark creates fire. Air in from intake. Take a compression and leakdown. These are two different test. This should tell you excactly whats goin on.
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