13 HP B&S overhaul

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  #1  
Old 06-08-04, 04:19 PM
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Unhappy 13 HP B&S overhaul

I have a 13 HP B&S (MTD) riding mower with a shattered rod and broken piston. The cylinder wall is real clean and undamaged. I was able to get all of the broken pieces of connecting rod out of the crankcase. My only concern is the journal on the crankshaft. It seems to be a little gouged and sticky. I used a little 00 steel wool on the journal and it seemed to smooth it right out. If the journal is a little less than perfect, will it be O.K. to install the new piston and connecting rod without too many worries? At what point is the journal surface bad enough to require a re-grounding?
 
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  #2  
Old 06-08-04, 04:45 PM
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Numbers please

Give me the engine #'s and I'll provide you with specs and regrind numbers. Also, be sure to check closely for any cracks in the crankcase wall particularly the area where the starter motor mounts (outside the engine) as well as the camshaft for any damage before you proceed.
 
  #3  
Old 06-08-04, 11:39 PM
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Hello Divekennene!

Don't use the crank with any blemishes. If you can scratch across the journal with your fingernail slowly and feel ANYTHING, then it is too bad to use. Some shops soak the crank in acid to remove the aluminum that is wiped on the shaft. Usually the journal is fine, it's just the aluminum from the rod that smears onto it and needs to be removed. As puey61 said, inspect for damage inside the engine block right behind where the starter is, and look at the camshaft and the camshaft bosses in the block. Many times they will get a crack in the boss. Check the wear in the balancer bushings too. Also when you replace the piston and rings, be sure to hone the cylinder to a good cross-hatch pattern to keep it from smoking when you get it back together (letting the rings seat in). Cut the ridge at the top of the cylinder too, and make sure the ring gaps are 120 degrees apart from each other around the diameter of the piston.
 
  #4  
Old 06-09-04, 03:07 AM
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Thumbs up Engine #'s

Here are the engine #'s:

Model # - 28T707

Type - 1154E1

Code - 000331ZE

Briggs and Stratton 13 HP Power Built

Thanks alot.

Matt
 
  #5  
Old 06-09-04, 04:12 AM
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And the numbers please

Standard bore is - 3.4365"-3.4375". Re-bore if worn more than .003" over 3.4375". Crankpin journal reject size is - 1.247" or smaller.
Note: To be measured properly, the bore should be measured in three different positions at 1/4" as well as 1 and 1/2" inches down the cylinder. Also, I use a 180 grit emery cloth to polish the crankpin journal until all dull areas are removed (the dull areas being aluminum build-up) and then make three measurements around the circumference in order to acurately determine the size of such. Let us know what your measurements are and we'll advise you further.
 
  #6  
Old 06-15-04, 05:56 PM
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Thumbs up Journal Measurements

Hi Folks,

Sorry for taking so long to get the measurements back. Here are the measurements that I got from the journal:
Reading 1: 1.255"
Reading 2: 1.255"
Reading 3: 1.254"

The cylinder is in suprisingly immaculate shape. It is still glass smooth all the way around, top to bottom. I did like you suggested and sanded the journal smooth (removing the transferred aluminum). It feels glassy like the cylinder now. I did not find any cracks or blemishes of any kind anywhere in the crankcase or on any other parts. I would like to believe that I should be ok to install a new piston, rings, connecting rod, and gaskets without too much difficulty. Any more advice is very much appreciated!

Thank you so much,
Matt
 
  #7  
Old 06-16-04, 12:56 AM
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Smooth and glassy is what you want on the journal, yes, ...but not the cylinder walls. They need crosshatch to seat together with the rings.
 
  #8  
Old 06-16-04, 03:23 AM
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You had better take another measurement of the crankpin journal with a known, good quality instrument. The absolute largest figure you should have here is 1.2493", if is any bigger then you likely still have aluminum build-up. Also, and although you say the bore "looks" good, you'd better measure this accurately and look for the crosshatch as cheese pointed out.
 
  #9  
Old 06-28-04, 03:03 PM
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Exclamation Help Please!

As it turns out, it appears that the crankshaft is bent. I opted to go with a new engine versus repairing this thing any more.

I received the replacement engine today. I have one major concern however. The new engines frame mounting holes are not threaded. The frame of the tractor has threads, and the mounting bolts are too large for the holes in the new engine. By looking at it, it appears I have two choices:
I can tap the mounting holes in the new engine, or I can get 4 new bolts and nuts that will fit the holes in the new engine. My only concern is that if I get 4 new bolts and nuts, they will have to be a smaller diameter (just barely) to be able to fit in the smooth bore holes, and as such they will no longer be able to thread into the frame.

P.S. The mounting bolts on the old engine went from the bottom up into the threaded mounting holes.

Any help would be greatly appreciated. My grass is really getting long.

Thanks,
Matt
 
  #10  
Old 06-28-04, 03:10 PM
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Originally the OEM, by design, installed 3/8 self-tapping screws. Discard these and use 5/16 bolts, flats, locks and nuts. This will be a much better means of securement than the original. Send the bolts up through and use the flats, locks and nuts on the top side. Length will be somewhat critical - you will have to measure up to determine the best length bolt needed.
 
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