riding mower

My MTD riding mower with a 17.5 Briggs and Stratton has been having a hard time rolling over when I go to start it. When I turn the key the starter will not roll over at first, it seems to struggle at first but the it turns over. It's almost as if there is to much compression to over come. The last two times I mowed my lawn after about 5 minutes there is a noticeable loss of power and then the motor starts to sputter and now has quit. I am thinking that it could be sticking valves or perhaps crankcase ventilation. Any comments/input would be appreciated. Thanks, CJ

On 6/10/2013 9:28 PM, cj wrote:
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Pull the spark plugs and see how it cranks.

On 6/10/2013 5:36 PM, Big Al wrote:
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I did and it cranks fine
cj

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I wish I had done that test with a neighbor's riding mower. He had the same problem, starter would not turn it over, even with a new battery and connecting the battery directly to the starter with jumper cables to bypass the solenoid and everything else. It would engage and try to turn it, but just could not. I was convinced it had to be a bad starter. He bought a new one and same thing.
He finally had Sears come out to fix it and they told him it was the valve adjustment. Sounded bizarre to me, especially since he as a small lawn, the mower wasn't that old, maybe 5 -7 years and otherwise worked fine. But apparently they rely on some sort of compression release system to reduce the torque required. When the valves get out of adjustment, apparently that must affect the compression release system.
The fact that it spins with the plugs out suggests you have a similar problem.

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*No expert here, but have you checked the battery lately? Is it getting charged? Do you have a spark at the plugs?

On 6/10/2013 5:36 PM, John Grabowski wrote:
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Battery if good and a year old starter
cj

cj wrote:
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Dirty gas filter or blockage of gas line? If you already checked that, please tell us everything you did check so we don't have to guess.

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try putting jumper cables from a vehicle to the mowers battery.
if it still cranks poorly that will elminate a battery or charging issue....
charging voltage with mower running should be around 13.8 at the battery, any lower and the generator isnt charging properly

On 6/10/2013 6:37 PM, bob haller wrote:
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I would expect to see a voltage of at least 14 volts but not as high as 15 volts. The best way to check it is with an ammeter. Even cheap multimeters will handle 10 amps DC. I doubt a riding mower charging system is going to put out more than 10 amps DC. ^_^
TDD

On 6/10/2013 5:28 PM, cj wrote:
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Could be a timing issue

CJ,
Overhead valves? Check and adjust your valves. They may be too loose.
Dave M.

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ose.
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+1 Here's a video for the OP:
http://www.youtube.com/watch?v
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On 6/10/2013 7:10 PM, Denis G. wrote:
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When I was servicing a lot of residential generators, I would have to adjust the valves on the engines after the things had been in for about a year or after a prolonged power outage from a storm where the gensets had been running for days. It wasn't all that difficult on the Generac generators that had the B&S Vanguard V-twin. The last one I installed had the Generac developed and manufactured big honkin' V-twin engine that seems to be bulletproof. ^_^
TDD

On Jun 10, 9:09 pm, The Daring Dufas <the-daring-du...@stinky- finger.net> wrote:
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too loose.
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I replaced the head on my neighbors riding mower last summer after it swallowed the exhaust valve when the valve guide came loose (supposedly common problem for that vintage - mid to late 90s). It was a 14.5 BS OHV and I went through the exercise for adjusting the valve clearance. He was ready to junk it, but I said that I could fix it cheaply for him and I got the parts from Sears. Out of curiosity I split the case and examined the part on the exhaust cam that does the compression release at low RPM. My neighbor replaced the battery this year, but it's still going strong.

On 6/10/2013 9:34 PM, Denis G. wrote:
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If it's the B&S Vanguard, it's actually a pretty good engine if you keep it serviced, especially changing the oil. I thought it was funny that the Vanguard used the same oil filter as my old 2.2L Dodge K-car. ^_^
TDD

On Jun 10, 10:09 pm, The Daring Dufas <the-daring-du...@stinky- finger.net> wrote:
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be too loose.
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The one that I worked on was a 28N707- single OHV 14.5 hp.

On 6/10/2013 11:51 PM, Denis G. wrote:
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Well heck, it's a horizontal engine like the Vanguard in the older 8kw Generac residential generators because the generator was belt driven and sitting vertically next to the engine. The valves should be just as easy to adjust. I think I have a piece of shim stock somewhere I cut to make it simpler to set the valve clearance of which I don't remember the value. Must be in some of those dead brain cells I lost along the way. Now when I write horizontal, I'm referring to the plane the flywheel and piston are in, the shaft is vertical. ^_^
TDD

On Jun 11, 12:59 am, The Daring Dufas <the-daring-du...@stinky- finger.net> wrote:
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may be too loose.
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^_^
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I’ve only seen the conventional horizontal/vertical engine naming to refer to the crankshaft orientation:
http://www.briggsandstratton.com/us/en/~/media/Files/FAQs/BriggsAndStratton /PDFs/numerical_designation_system.pdf
I found my valve clearances here: http://www4.briggsandstratton.com/miscpdfs/RNT/Engine%20Specifications%20Ch art_ms3992.pdf
I used 0.006” for intake and 0.010” for exhaust (+/- .001”) for the engine I worked on.

On 6/11/2013 9:41 AM, Denis G. wrote:
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http://www.briggsandstratton.com/us/en/~/media/Files/FAQs/BriggsAndStratton/PDFs/numerical_designation_system.pdf
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http://www4.briggsandstratton.com/miscpdfs/RNT/Engine%20Specifications%20Chart_ms3992.pdf
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The overhead valves are a heck of a lot easier to adjust than the old valve in block designs. I've actually used a propane torch to heat up the older valve in block engines to get them to run. ^_^
TDD

Had an oil change recently, and good quality brand name oil? . Christopher A. Young Learn more about Jesus www.lds.org . .
My MTD riding mower with a 17.5 Briggs and Stratton has been having a hard time rolling over when I go to start it. When I turn the key the starter will not roll over at first, it seems to struggle at first but the it turns over. It's almost as if there is to much compression to over come. The last two times I mowed my lawn after about 5 minutes there is a noticeable loss of power and then the motor starts to sputter
and now has quit. I am thinking that it could be sticking valves or perhaps crankcase ventilation. Any comments/input would be appreciated. Thanks, CJ