Briggs 28N707 15HP Died and Won't Start - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 27 Old 08-03-2019, 02:49 PM Thread Starter
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Briggs 28N707 15HP Died and Won't Start

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!
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post #2 of 27 Old 08-03-2019, 02:50 PM Thread Starter
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Re: Briggs 28N707 15HP Died and Won't Start

Should also mention this is an OHV. Exact model is 28N707 0160-01, so it's fairly old.
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post #3 of 27 Old 08-03-2019, 05:06 PM
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Re: Briggs 28N707 15HP Died and Won't Start

I would check the compression. If you have fuel and spark you need compression of course to run you must have spark at the right time.
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post #4 of 27 Old 08-03-2019, 05:48 PM
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Re: Briggs 28N707 15HP Died and Won't Start

I would take the flywheel off and directly check the key. It may look intact, but the only thing that 'happened' was the extra load of the grass.

Otoh, if the governor tried to open the throttle, and tried a bit too hard, it could have messed up the linkage or the internal governor parts.

Does the throttle open all the way when you move the hand control to the fast setting? It should, and the governor link should let it. You should be able to move the governor arm back and forth, and feel a slight resistance as the bobbin moved up and down on its shaft. If the governor arm just flops, I suggest dis-assembly and inspection...
tom

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post #5 of 27 Old 08-03-2019, 05:56 PM
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Re: Briggs 28N707 15HP Died and Won't Start

I assume head gasket was new when you did the rod?
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post #6 of 27 Old 08-03-2019, 06:30 PM Thread Starter
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Re: Briggs 28N707 15HP Died and Won't Start

Thanks, I'll rent a gauge from autozone and check it out. Seems odd that it would lose compression while mowing unless something catastrophic happened?
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post #7 of 27 Old 08-03-2019, 09:35 PM
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Re: Briggs 28N707 15HP Died and Won't Start

I was cutting with a tecumseh vtwin when I lost enough power that I couldn't turn blades. Then a no start. Blew head gasket on one side and I think other side has renewed carb issue. Twin carbs on it.
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post #8 of 27 Old 08-03-2019, 10:18 PM
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Re: Briggs 28N707 15HP Died and Won't Start

If it blows you finger off the plug hole it has enough compression to run.
What to look/feel for is the blow blow blow on your finger and never a sucking of your finger back into the plug hole.
This happens all the time when the rocker studs come loose and bend pushrods or a valve guide slips and bends push rod or rods.

If it blows blows blows and no sucking back in and no double blow (if a valve in not opening) and the timing is right and it has strong spark it will run on starting fluid or by pouring gas into intake.
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post #9 of 27 Old 08-04-2019, 08:48 AM Thread Starter
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Re: Briggs 28N707 15HP Died and Won't Start

Tom- throttle does go the fast setting. I'll check out the gov this morning, and go ahead and pull the flywheel to inspect the key. But it does look to be aligned with the keyway so wouldn't it be in time regardless?

38racing- Brand new headgasket was done with the rod. It wasn't showing any signs of failure before it quit as far as I could tell.

Toby- I'll give that a try and see how many blows I get haha.

much appreciated guys
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post #10 of 27 Old 08-04-2019, 10:27 AM Thread Starter
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Re: Briggs 28N707 15HP Died and Won't Start

Alrighty... pulled the flywheel and the key is fine. Kind of wish it wasn't because that's cheap and easy...

Compression reads just over 70 psi.

thoughts?
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post #11 of 27 Old 08-04-2019, 03:10 PM Thread Starter
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Started reducing the valve lash until the tractor wanted to start. Now it will turn over, but just barely, and it won’t stay running long. Reducing the throttle seems to help but it still dies....

Here’s a video of it if anyone has ideas

https://youtu.be/H6q7xMSBsEI
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post #12 of 27 Old 08-04-2019, 05:48 PM
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Re: Briggs 28N707 15HP Died and Won't Start

It certainly looks like a timing or valve issue. How does the governor arm feel? Is it floppy or does it have limits?

Those engines have auto decompression so you wont get an accurate reading unless you pull the exhaust rocker off the valve and pushrod to disable it. A leak down tester would tell you more than a compression gauge in this situation. I would think it would still be over 80 psi even with a decompression valve so 70 seems kinda low. Put a little oil in the cylinder and see what it does. If it goes up a lot you have bad rings. If it goes up a little or none you have a bad valve.
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post #13 of 27 Old 08-04-2019, 06:47 PM
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Re: Briggs 28N707 15HP Died and Won't Start

Quote:
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?

Those engines have auto decompression so you wont get an accurate reading unless you pull the exhaust rocker off the valve and pushrod to disable it. A leak down tester would tell you more than a compression gauge in this situation. I would think it would still be over 80 psi even with a decompression valve so 70 seems kinda low. Put a little oil in the cylinder and see what it does. If it goes up a lot you have bad rings. If it goes up a little or none you have a bad valve.
Decompression is on the intake. You hould see the bump at tdc. Might be ground into the cam on that model.
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post #14 of 27 Old 08-05-2019, 05:37 AM
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Can you confirm that the anti-backfire solenoid on the carb bowl is working? It makes an audible click when turning the key to the run position. You may be able to feel it if you put your hand on it also.
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post #15 of 27 Old 08-05-2019, 10:46 AM
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Re: Briggs 28N707 15HP Died and Won't Start

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Originally Posted by B440 View Post
Can you confirm that the anti-backfire solenoid on the carb bowl is working? It makes an audible click when turning the key to the run position. You may be able to feel it if you put your hand on it also.
Forgot about that. OP should do simple test of spraying carb cleaner into air intake and see if it fires. I had one shutoff off because keyswitch went bad and power to the AntiBackfireSolenoid failed.
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