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Discussion Starter #1
Hey guys! Man, if y'all can help me, I'll be happier than a dog up a bone tree...My mower won't start. It tries to turn the engine over, but seems like the engine is too hard to turn. I've replaced the starter, solenoid, battery (then charged the battery), cleaned all the tetminals, and tested and confirmed with a multimeter that 12V is getting to the starter when I turn the key. The starter engages, but now won't produce enough power to spin the engine...and if I hold the key in the start position, the starter starts smoking...To make it more complicated, when I first replaced the starter, it worked for a few weeks or so, then started failing to start my mower, so I replaced the battery, and that again fixed the problem, but only for about 2 months, and now it's doing the same thing again. So now I can't tell if it's even an electric problem or maybe something in the engine, making it hard to turn and wearing out the starters...
 

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Discussion Starter #2
So some new info...when we took the spark plug out, but left it connected to test it, the engine spun freely, but when I put it back in, it went back to struggling to turn it over...
 

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Discussion Starter #3
...Seems like a compression issue, since it'll spin with the spark plug out...I also tried jumping it from my truck directly to the starter (with the spark plug in), but still not enough power to spin the engine more than once.
 

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Could be valves or bad connection. Not only battery terminal connections, but also frame ground or more unlikely starter ground. 12v can travel through an almost nonexistent connection, but amperage can’t. Don’t cost anything to check those out. Valves might be the better starting point, though.
 

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Discussion Starter #6
Thank y'all! It's a Briggs 17.5hp engine, model # 31R977. I'll see if I can figure out how to adjust the valves and test amps. How can testing amps be done for free? Thanks again!
 

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Don’t have to test amperage at this time. But if you did, clamp meter. I guess they aren’t free, but maybe $20. Great diagnostic tool to have for many occasions. Bad connection (frame ground, a possible culprit in many bad connection cases) won’t allow the amperage required to spin the starter to pass through.
If valves are out of adjustment or automatic compression release mechanism (if engine is so equipped, as I’m not hugely familiar with that model) is out of whack, it’s definitely pulling more amps than it should be anyways.
 

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Discussion Starter #9
I adjusted the intake to .004 and the exhaust to .006, which didn't work, so I went by another source and adjusted them both to .005, but there's still a compression issue, making it hard to turn, so I don't think there's an amperage problem. And it's a 2018 engine, so seems a little soon to be having a major problem like this...But any ideas on where to go next? Thanks!
 

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Did you look at how those valves are to be adjusted? Some B&S engines you adjust at TDC, while others might be adjusted 4* BTDC and I think some are 5* ATDC, according to what engine you have. You need to adjust at what the engine manual says to adjust at, or you wind up with what you now have, hard starts of compression lockup.

I have heard of some B&S engines having plastic compression release valves and the arm breaking, which no matter of valve adjustments worked until the part was replaced, and this requires a teardown. Hope this is not your case, but money counters are always trying to save a couple cents, at the cost of the consumer.

Plugs out and cranking easily says, improper valve adjustment or compression release valve not working correctly.

OK, it took me some time to find your model of engine, but I see that this B&S is the INTEK model.

You adjust the valves by bringing the cylinder up to TDC on compression stroke(both valves closed and plug ready to fire), then moving the piston just past TDC by 1/4" to adjust valves.

Intake: .003-.005"
Exhaust: .005-.007"

Del
 

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Discussion Starter #11
Thank you! I used this video (and manual specs) as a guide, and didn't measure where the piston was...think I should do that again and measure where the piston is with a long screwdriver or something before looking at the camshaft?

https://youtu.be/sztd7YP4IZY
 

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Discussion Starter #12
Looks like probably the compression release mechanism on the camshaft, so I'm about to crack open the engine and see. Ugh.
 

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Discussion Starter #13
So I just replaced the camshaft. The compression release mechanism (arm) was broken off, so I assumed that was the issue, but after spending all day on that and putting everything back together, it's still doing the same thing...barely spins the engine once, maybe, and that's it. The battery does need a charge at this point, but the engine still seems to have a compression issue, since it's still hard to turn manually. So I'm thinking maybe I didn't adjust the valves right...but if that's not it, I'm lost...
 

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I was having a similar issue on a 20 hp B&S. I followed a YouTube video to adjust the valves and the problem was gone. Sorry yours is a little more complicated. If the starter was smoking, there’s no problem with connections, but you may have damaged the starter windings.

All else fails, go to a local repair shop that you trust. That’s how I found my problem, over the counter advice at $0. Then I bought the valve cover gaskets and the breather tube that I broke, since it was super brittle. If you can’t fix it, it’s useless until it is and an expert might get you there quicker. I know, we always want to fix it ourselves, but sometimes we just have to bight the bullet and take it in. This time of year might be a little slower for them and it won’t take too long/cost too much.

Good luck
 

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make sure the stud bolt on the rocker has not backed out also while turning by hand should see the little bump for the compression release if it is working properly
 

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Discussion Starter #18
Thanks! So...fixed my compression problem! The pin for the intake valve didn't go back in right when I replaced the camshaft, so I put it back in, adjusted the valves (right this time), and actually got it to start! Unfortunately, now it's acting like it can't get fuel for some reason...ugh. Any ideas?
 

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Discussion Starter #19
Basically, it was firing good, but I had to adjust the throttle cable a bit...one of the times I was trying to start it, it just kinda stopped firing. It's still turning over and spinning the engine, but doesn't seem to be getting gas now...
 
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