Briggs Hard to Turn Over - Air coming out of valve - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 25 Old 09-07-2019, 10:47 AM Thread Starter
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Briggs Hard to Turn Over - Air coming out of valve

Hi all, been a while.

I have a briggs that is very hard to start, technically, it won't. It will struggle to trying to turn over.

It seems like the culprit might be a bad compression release, but i'm not sure if this motor even has one. It's a 311777. For what it's worth, I turned the motor to see if the one valve will dip just a bit (compression release), but it does not do that.

I'm wondering though if something like a bad gap on the valve could be to blame. I set them a while ago but when i tested it today, they were very close (i couldn't get a .003 feeler gauge through when it calls for 003-005.

The only clue i have is that, when i turn the engine by hand, i can hear a hiss of air trying to come out of a valve, i'm not sure which one. Can anyone give me a reason as to why this would be? Is it normal? I would think not.

Anyway, thanks for any advice. I have a video where you can hear it. It's a struggle to even turn the engine by hand with a 14" wrench. https://imgur.com/a/OfJNegM
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post #2 of 25 Old 09-07-2019, 12:32 PM Thread Starter
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Re: Briggs Hard to Turn Over - Air coming out of valve

just an update. i went and reassembled the valves just to make sure everything was seated right and adjusted the gaps more closely to spec. i removed the springs and pushed in the top rod beneath the spring in some, the motor could turn by hand much more freely. so i put everything back together thinking maybe it was a valve adjustment, still hard to turn. if i push in the valve by hand while im turning, it frees up the flywheel and makes it easier to turn. here's a link to a video showing what i mean - https://imgur.com/a/Bb8233a
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post #3 of 25 Old 09-07-2019, 05:16 PM
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Re: Briggs Hard to Turn Over - Air coming out of valve

Have you removed the sparkplug yo see if it turns freely? I have to assume though that you did because it's pretty much the only way to find 1/4 inch past TDC to do valve adjustment. The compression release works on the intake valve. The other reason to crank with plug out is in case you have flooded gas and oil into cylinder and it's hydrolocked.
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post #4 of 25 Old 09-07-2019, 10:41 PM
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Re: Briggs Hard to Turn Over - Air coming out of valve

The bottom one is the intake on a 31 series (and most briggs) and should be the one the compression release (ACR) "bumps" open right after it closes.
The gap for the intake is .003-.005 and the exhaust is .005-.007. Valve on this one are set at piston 1/4 inch down past TDC compression stroke.

After you adjust valves if you have no ACR bump you cna get it to start by turning it past the compression stroke or backwards away from it and then remove air filter cover and hold your hand over the intake to block all air. Then crank it. It should be enough to get past the hump and start up.
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post #5 of 25 Old 09-09-2019, 08:27 AM Thread Starter
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Re: Briggs Hard to Turn Over - Air coming out of valve

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Originally Posted by 38racing View Post
Have you removed the sparkplug yo see if it turns freely? I have to assume though that you did because it's pretty much the only way to find 1/4 inch past TDC to do valve adjustment. The compression release works on the intake valve. The other reason to crank with plug out is in case you have flooded gas and oil into cylinder and it's hydrolocked.
Hi 38. Yes, I removed the spark plug and it was able to turn over freely by hand and via starter. I started turning the engine with by energizing the post on the starter and it spun with no issue. I watched the spark plug hole to make sure there was no liquid spitting out, there wasn't any. I also watched the valves (i kept the cover off), and they seemed to be functioning normally. once i replaced the spark plug, the starter couldn't get it 1 rotation.


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Originally Posted by TobyU View Post
After you adjust valves if you have no ACR bump you cna get it to start by turning it past the compression stroke or backwards away from it and then remove air filter cover and hold your hand over the intake to block all air. Then crank it. It should be enough to get past the hump and start up.
Hi Toby, i did see this trick somewhere but couldn't get it to turn, though you have given me more info (turning it past compression stroke / backwards), so i will give that a shot. thanks.
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post #6 of 25 Old 09-09-2019, 09:10 AM
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Re: Briggs Hard to Turn Over - Air coming out of valve

You have to block off all the air flow going into the intake for this to work. It's amazing what a difference it makes.
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post #7 of 25 Old 09-09-2019, 09:33 AM Thread Starter
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Re: Briggs Hard to Turn Over - Air coming out of valve

just curious, can the motor run, at least for a short time, with with the valve cover off? Would like to readjust valves if i can get it started but would like to skip the step of putting it back on / taking it off.

thanks.
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post #8 of 25 Old 09-09-2019, 09:49 AM
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Re: Briggs Hard to Turn Over - Air coming out of valve

It can and will ,but you do not adjust the valves with it running on a small engine--some oil will likely spray out of the push rod area if you run it with no valve cover..


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post #9 of 25 Old 09-09-2019, 01:11 PM
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What size battery are you using? How many amps? Have you had the battery tested? Unless you weren't at tdc when you did the valves everything you've described sounds normal. Make sure you've got a good, full charged battery. Go to Menards and get the big one and give her hell!
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post #10 of 25 Old 09-09-2019, 01:34 PM Thread Starter
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Re: Briggs Hard to Turn Over - Air coming out of valve

lol i won't be trying to adjust valves while it's running, i'd love to see someone try.

as for power, i've tried jumping it from another rider, jumping it from a car battery and one of those little power pack jumpers (which i managed to destroy in the process)... there's just a lot of compression, its tough to spin it using a wrench by hand. when i remove the spark plug or push in one of the valves, it turns like it should.
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post #11 of 25 Old 09-09-2019, 01:42 PM
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Do you have a compression tester? I'd be curious that the actual pressure readings are
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post #12 of 25 Old 09-09-2019, 02:14 PM Thread Starter
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Re: Briggs Hard to Turn Over - Air coming out of valve

unfortunately i do not. when i try to spin the engine with a wrench, i can hear the air trying to escape out of what i believe to be the valves. it's almost like it's hydrolocked, but with air since there's nothing in there. nothing can escape (well it does, slowly hissing out of a valve, it's possible it could be another close area).
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post #13 of 25 Old 09-09-2019, 02:56 PM
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Re: Briggs Hard to Turn Over - Air coming out of valve

It's not that anyone would try to adjust them with it running, is that you do not adjust them once they're warm. All valve adjustment on Briggs & stratton's are done on a cold Engine with the Piston 1/4 inch down past top dead center. You don't need to get them warm every checked them because you're reading this would be wrong.
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post #14 of 25 Old 09-09-2019, 03:13 PM
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What you're hearing is probably air escaping slowly around rings into the crankcase.

Explain how you found TDC when you adjusted the valves. Your cam (if I remember right) is solid and has no moving pieces for compression release. It's a special cam lobe and if you adjust valves at tdc instead of 1/4" past TDC, you effectively just eliminated your compression release feature.

To adjust, take out the spark plugs and rotate the engine until you see the intake valve open and then close. Once it closes, put a screwdriver down until it touches the piston. Rotate until the piston is at TDC (piston stops moving). Turn for another 1/4" so the piston begins to retract on the compression stroke. Both rockers should now be loose, and this is proper location for valve adjustment.
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post #15 of 25 Old 09-09-2019, 03:43 PM Thread Starter
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Re: Briggs Hard to Turn Over - Air coming out of valve

thanks for that info toby, i did not know that the engine should be cold to test the gaps.

hi bacon, yes, that is how I adjusted the valves. you're saying that this motor does not have the compression release feature?
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