Briggs and Stratton 12 HP Motor replacement


Hi,
I have a 5 year old Murrary 12HP. 38 (or 40)" riding mower .. and I want to keep it simply because last year I moved and I bought a rear bagger that works really well and if I got rid of it's another $1800 or so to replace the whole setup.
My main problem is it tends to lose power after awhile .. 15 or 20 minutes. I've replaced the spark plug and fuel filter .. but I haven't had it looked at by real small engine repair place simply because it takes *weeks* to get these things looked at ! I's a headache getting it to a shop because it needs trailered.
I use to have a Sear 15HP it that thing hauled ass .. until I bent the crank shaft and ruined the engine.
This Murray is slow .. and even in 6th gear ... It's slow .. Then it gets slower after 15 minutes !
Whats the possibility of replacing the engine with a new one , and maybe even larger size ?
PS: The muffler kept falling off and in my 2 attempts at repairing THAT issue the mounting holes are ruined and I run without a muffler too. It was running slow before that happen however. Now I have a SLOW and LOUD mower !
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Pretty good. Check Northern Tools, they supply small engines such as this. You may be surprised how expensive motors are.
If you'd like, we can offer some ideas what the low power problem might be. I've got a few ideas right off the top of my head.
No ideas come to mind for the muffler, though.
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A weak ignition module can cause it to get weak after it heats up, or low compression, check it out first.
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That's more a problem of gearing than power, I agree Murrays are slow, I recently transferred the engine out of a worn out MTD to a Murray, and in top gear a person could out run it without breaking a sweat, I could catch dogs and cows with the same engine in the MTD (Which is likely why it was worn out.) You do have an engine problem though RE: 15 min

Most of the engines have similar mounting schemes, drilling a few holes in the frame wouldn't be a big deal, the pulley for the blades / transmission would need to fit the shaft though. Even at that I've had machine shops bore them out if too shallow or too narrow

You could drill out the holes and helicoil them.
Philosophical statement; you could probably pick up a used mower on Craigslist for the price of a new engine that you would be happier with.
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Eric in North TX wrote:

Yeah ... buying again has crossed mu mind but my luck with used (motorized) crap is exactly that .. used .. Crap !
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Are you sure your gas cap is vented? I had this happen on small push mower but the tank was smaller than a tractors tank so it would take longer to draw a vacuum on the larger tank until you start starving the engine for fuel. Try running the engine the way it is and when it starts slowing down at fifteen minute mark unscrew the gas cap enough to seeif that helps. If it helps then you have a non venting gas cap, replace the cap with a proper venting one. If that didn't do it I haven't a guess what more it could be.
I might be selling an 16hp Briggs come spring.
Rich

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When something takes time to fix and out of service a hassle I go redundancy!
I have two walk behind lawn mowers, 2 washers, 2 dryers, 2 vacuums, 2 vans.... both 1992 and 94 matching caravans.
sure it costs a little more but when something breaks all the pressure is off me.
so pick up a used rider and get the other one serviced.
i buy lots of stuff at flea markets really cheap. like my 2nd mowert was 20 bucks. if i somehow destroy it no biggie. a friends family bought a new 800 buck mower the same time as mine. both lawns look about the same, my carb fell off once, they have had their mower back twice for repairs
hey the dryer broke isnt a disaster, its a ahh use the other one till i get a minute to fix it
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Where do you put the spare garage and house to keep it all?
snipped-for-privacy@aol.com wrote:

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Rich wrote:

Excellent thought ! I'll try that next time.
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Enter,
I'd look at the drive belts. If they are old they may be slipping. When they start slipping the higher gears are most obviously affected. 5 yrs doesn't sound like a long life for drive belts though. This doesn't sound like an engine problem. Someone else has already suggested helicoils to fix the muffler problem. If the muffler bolts kept working loose perhaps you should use thread cement.
Dave M.
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David Martel wrote:

The belts I've thought of only in the sense of making the puller LARGER so it when spin faster .. thus a higher RPM at the spindle.
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Have you checked your spark plug? Check that it doesn't have a whitish deposit showing a lean mixture is causing the motor to overheat
David
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