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 Help! B&S 15 hp OHV troubleshooting

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Timrsnakess
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PostSubject: Help! B&S 15 hp OHV troubleshooting   Help! B&S 15 hp OHV troubleshooting Icon_minitimeFri Jan 01, 2016 9:47 pm

I have this briggs 15hp ohv 28ci (correct me if im wrong) that i had trouble getting to crank. it was turning over really slow even after i adjusted the valves to spec. then i rebuilt my current starter thinking it was that, still nothing i then ordered a new one, nothing, still cranking hard, it wouldnt even turn over completely w/o hand turning it. so I think something internally is binding.  when i first got it the other guy had the same problem but the gas was mixed w/ oil so im suspecting that he ran it like that until it got to the point where it wouldnt crank
I pulled the head off today and it didnt look all that bad here are some pics:

Help! B&S 15 hp OHV troubleshooting Img_2410

Help! B&S 15 hp OHV troubleshooting Img_2411

Help! B&S 15 hp OHV troubleshooting Img_2412

Im thinking it's bottom end any input would be appreciated Very Happy
sorry the images are so small, just click on em
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prancstaman
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PostSubject: Re: Help! B&S 15 hp OHV troubleshooting   Help! B&S 15 hp OHV troubleshooting Icon_minitimeSat Jan 02, 2016 3:40 am

Cylinder looks in good shape. If there was a problem with the piston to cylinder wall issue, you would see gouges in the cylinder wall. Try cranking it with the head off, should free spin really fast, if there is a problem with the bottom end (crank,piston,piston rod) it would show up cranking it with the head off. If it is still giving a problem cranking with the head off, then turn it by hand, this would verify that there is a problem with the bottom end of the motor if it is hard to turn but make sure your clutch is fully disengaged from the belt too. The belt might be grabbing the pulley just enough to keep from starting. If everything checks OK, you would know if it wasn't, then the next step would be electrical. You said that you put a new starter on it, OK. I'm thinking maybe a bad electrical connection somewhere else. Could be on battery, solenoid, or where the wire connects to starter. Look for frayed wires on connectors too. Plus make sure you have a good ground path going to the frame, then to the battery. Also look for frayed wires there too. Check battery voltage. Should be 12v or higher, 11v or 11.5v would be on the edge of battery not having enough voltage to crank the motor while motor is together. Maybe hook up jumper cables to battery from a car to see if the battery is not strong enough. 10v in the battery would be a bad cell in battery.

Hope it helps.
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Timrsnakess
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PostSubject: Re: Help! B&S 15 hp OHV troubleshooting   Help! B&S 15 hp OHV troubleshooting Icon_minitimeSat Jan 09, 2016 10:25 pm

Ive got a lot more torn apart in the last week or so after school and any free tome trying to figure out what is wrong with this motor. i pulled the sump cover off and governor and cam and all of that good stuff and a few things concern me: first after looking inside for a fe minutes I started seeing some score marks around the cutouts enabling the connecting rod to move w/o hitting the block
Help! B&S 15 hp OHV troubleshooting Img_2414
Help! B&S 15 hp OHV troubleshooting Img_2415
I also noticed that the rod cap bolts had some evidence of someone being in there to tighten them
Help! B&S 15 hp OHV troubleshooting Img_2417
let me know what you guys think thanks!
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MasonMcK
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PostSubject: Re: Help! B&S 15 hp OHV troubleshooting   Help! B&S 15 hp OHV troubleshooting Icon_minitimeSat Jan 09, 2016 11:13 pm

Those marks on the clearanced areas of the block are nothing to worry about. They are from when the cast engine block was machined at the factory. If the rod was contacting the block, there would be a big chunk of metal broken out of it since cast materials crack easily. I think that you will not find anything inside the bottom end that is the issue; other than possibly a seized main bearing... But even that is doubtful. I think that it is definitely electrical related probably a bad ground or a fried battery.
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prancstaman
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PostSubject: Re: Help! B&S 15 hp OHV troubleshooting   Help! B&S 15 hp OHV troubleshooting Icon_minitimeSat Jan 09, 2016 11:43 pm

Looks like crank and rod was not hitting. No contact marks. Tool marks on the bolts is nothing, they got to put the motor together at the factory. To make sure, grab the piston rod to see if it's worn by pushing and pulling on it to check for play. Side to side play between crank weights is OK, up and down from cylinder is bad. Means the circle is worn but I got a feeling it will be OK. Since you got the motor apart, does the cam shaft have an easy start mechanism on it? Could be worn to where it's not dumping pressure on start up. If the cam shaft is one piece then it doesn't have an easy start mechanism on it.
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Timrsnakess
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PostSubject: Re: Help! B&S 15 hp OHV troubleshooting   Help! B&S 15 hp OHV troubleshooting Icon_minitimeSat Jan 09, 2016 11:53 pm

Oh i forgot thats another thing, the decompression doohickey on the cam, I meant to mention this. when I first got it out it didnt seem to be springing back, the spring got caught in between the cam and the actual arm of the decompression thing. it seems to look fine and work fine now that i got the spring unstuck, it doent look worn or anything sooo... could this possibly maybe be my problem? I really dont know thanks
Help! B&S 15 hp OHV troubleshooting Img_2510
Help! B&S 15 hp OHV troubleshooting Img_2512
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prancstaman
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PostSubject: Re: Help! B&S 15 hp OHV troubleshooting   Help! B&S 15 hp OHV troubleshooting Icon_minitimeSun Jan 10, 2016 12:53 am

I'd say Yes, that's your problem with starting. How it works is when starting the engine, the compression is to much for the starter to turn it over on the compression stroke so engine designers figured to dump the compression by opening one of the valves to dump pressure, usually the exhaust valve, to make it easier to spin on start up. Now when the engine starts running, the mechanism is made to move out of the way, usually by centrifugal force, for normal running. Sounds like it was stuck in the running position to where it was not dumping compression on start up. Good job, should be fixed.

When you put it back together, take note on cam position so when you adjust the valve, the valve lifter is not on the mechanism when gaping the rockers. Maybe before putting the bottom cover to the motor back on, mark the flywheel in a certain spot to the engine block so you know for sure that the valve is closed all the way and not on the easy start mechanism.

If you adjust the rockers while the mechanism is pushing the valve open, you would be adjusting the purpose of the mechanism out of the mix of things to where it wouldn't be working right, to where it won't be dumping pressure on start up. Hope this helps.
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PostSubject: Re: Help! B&S 15 hp OHV troubleshooting   Help! B&S 15 hp OHV troubleshooting Icon_minitime

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