Murray 12.5/40 Update

This tractor has been doing a lot of the mowing.  Burns some oil but it is managable.

Yesterday the deck got fouled with the rear wheels.  Turns out whoever removed the hood brackets failed to notice the same bolts held the front axle in place.  4 new bolts fixed that.

New air and pre filter.

Briggs 31X707

Scored another of the OHV single cylinder briggs variety.  Have not looked at it much but it is in the 31 family but without pressure lube or filter.

Took it to the car wash and removed the head.  Definitely a busted con rod.

 Cylinder bore is .013" in the wear axis top and .002" at the bottom.  I will know better when I pull the pan and get a reading on the virgin bore area.  So the block would need a rebore to be useful.  I would rather spend the money on one of the similar engines with pressurized lubrication and oil filter.

Unfortunately I got oil on the camera lense at this point.

The head gasket was not blown and came off clean.  Good enough for testing another engine but I am not sure if it would be dependable.

The outside was covered with oil so I am guessing they were topping it off frequently.

My guess is that it started using oil and got so bad they ran it out of oil and blew the rod.





This makes my 4th engine in this family.  3/4 have worn out bores.

Engines of the 31 OHV variety
31A good condition unknown history, found junked
31B worn bore 200 hours from a JD Zero turn
31C worn bore (but running) in craftsman DYT4000
31D no pressure lube, worn bore, busted rod, unknow history

Briggs 28M707 1186-E1 9711197A

Landed another Briggs 13HP L head.   The spark plug looked very good.

It has a broken rod but there is only minor damage to the bottom of the cylinder.

I need to inspect for cylinder wall scoring in better light but I am thinking it is good.

The rod journal is covered with aluminum.   IRRC some acide maybe muriatic will remove it.

Cylinder is a bit on the oval side in that it is .001" in the virgin area. Taper on the wear axis is .004" for at total of .005"

Go-putz's engine is about .013".




I have been saving old ziplock back from the kitchen and have made generous use of them while disassembly.

The oil in this engine was approaching the viscosity of jello.  Not sure what was going on with that.

Plan is to rebuild this engine using parts from one of the other similar engine.  The original piston and rings will be retained and no boring or honing should be required.  I am not sure if it will go onto go-putz or the  Murray 12.5/40.

So I will need a minimum of a pan and head gasket.  But first I need to get the parts washer going.

Murray 12.5/40's History

The world is even smaller in a small town. 

I needed to deliver a front axle to a friend's place. I hooked the two wheel cart to the 12.5/40 Murray and headed out. The friend told me he had once owned this Murray, he put the 18HP twin on it and that he had already given me the 12.5HP briggs that belonged on it! And the mower originally belonged to an elderly lady who lives about a block away from me.

The original engine needs a rebore but somehow having all the original bits make putting it back appealing.

This was actually my second attempt at delivering the axle today.  The first time I ran out of gas 1/2 way there and my wife had to rescue me.  (and even brought me a cold beverage too!)

Murray 12.5//40

 

Finally found a LT with a briggs opposed twin!   Heard about it at coffee this AM and purchased it when the fellow came home from work.   Just got home with it so I have little idea what condition it is in.  The machine came from another scrapper (not Johnny) at the very reasonable price of $20.

Here is what I do know.  Engine turns and has some compression.  Transaxle shifts in and out of gear.  All the tires are up and the rear 2 have tubes.  One of the original back tires is toast but it came with 5th tire that does hold air.  Throttle cable seems OK but the choke is a patch job that will have to be replaced with OE.  Seat look good.  Missing headlight lense.

Tractor Data Tag

40702X92F

40 inch deck
type 702
made for 92F

Engine Data Tag

42 ci
Series 2
7 - Vertical
0 - Plain bearing non flage mount
7 - 12V Electric Starter

Made in 91

422707 1510 01

Wednesday, April 22, 2015

Dit the initial assessment.   A car battery hooked to the existing dead battery will not start the engine. Cranks too slow.  But jumping directly to the starter will.  Need to see if unhooking the dead battery will allow it to start with the jumper to the battery cables.

Engine starts and runs nicely on carb cleaner.  The plugs look good.   Compression seems good.

Split the carb and cleaned a bit of gunk out but did not go through it.   Cleaned the gas tank and replaced the line and filter.

Found out the hood mounting brackets are missing.  The muffler on the tractor does not exit where there is a cutout in the hood.  Hmmm


Friday, April 24, 2015


The tractor originally came with a 12.5HP single cylinder.   Made a trip to the roll off and one to the car wash today.   The battery will start it sometimes and not others.

Monday, April 27

Flushed the engine with karosene twice and refilled with rotella t.   But even though I was careful to drain the karosene the engine now rattles and I plan to change it again.

Briggs 6HP Mowers

I was asked to fix a broken shroud mounting hole on the mower for a friend.  Of the six or seven unknown mowers I had on had I found 3 with similar if not identical engines.

I used JB Weld to glue a bolt into the broken out hole from the back forming a stud.   Now it was impossible to put the shroud back on because the recoil started and the stud are at right angles.  I drill the rivets and removed the recoil housing.  This allows one to put the shroud on then bolt the recoil to the shroud.  Need to wait till Monday to find hardware to bolt the recoil to the shroud.  Hoping to find speed nuts.

Clogged Breather

I have been hearing about the stuck breather problem but had never seen one till yesterday.   It was interesting.

I had the head off a junked mower to inspect the cylinder bore.   Turning the engine by the flywheel created enough positive pressure in the crankcase forcing large amounts of oil out the lower valve.  Think pump.

There is no way this engine could run as it would instantly foul the plug.    Blowing into the breather cleared the problem.

This is interesting enough that I may make a video.