Murray/Briggs & Stratton Blown Engine Repair ~Connecting Rod Failure~



I went to use my 21 year old Murray Select 22″ mower, I heard some knocking, a loud pop, then the engine stalled. I instantly suspected a connecting rod failure. I was correct. This video shows what happened and the repair I made.

**Still running fine as of 5/10/2015**

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24 thoughts on “Murray/Briggs & Stratton Blown Engine Repair ~Connecting Rod Failure~

  1. I have an almost brand new 6HP mower this happened to. It was given to me so no warranty return. I haven't got it all the way apart but so far no case damage.

  2. maybe you can help me please and thank-you  So my Briggs and Stratton 3.5hp lawnmower engine doesn't turn so well.  If I manually turn the blade with my hand about 280 degrees of a rotation i feel a lot of resistance to the turn.  The 80 degrees left it is met with little to no resistance.  Do you know what it can be?

  3. if you used the main part of the other case, did you use the other connecting rod? you said it was new… but it looked used.
    I have a B&S v2 and looking for another one for parts as these usually lose one cylinder.

  4. so you are saying that the right new or different connecting rod can be bolted to the old crank without worrying about tolerance or play?

  5. Was there any considering welding the Rod? I think 5 places would scare me, however if it was a clean break, would think it might not be a bad idea. Thinking though that it might be that cheap pot metal that makes it impossible impossible to weld though.

  6. Lack of oil is basically the only reason for connecting rod breakage. I recently took apart a 4 hp B&S engine on a Murray 22" lawnmower that was given to me. The paint on the mower deck was still shiny and the muffler was still silver in color instead of the typical brown rust color. This tells me the mower was fairly new. When I disassembled the engine there was barely a thimble full of oil in it and it was very dirty and black. I was surprised to see a nylon cam gear and cam lobes on a metal shaft. It appears as if B&S is cutting corners to save money. The quality of the newer engines doesn't compare with the older ones. As long as you maintain the proper oil level and change the oil once in awhile, these engines will run forever.

  7. I had the same problem recently with my B&S 6.75 hp mower. Unfortunately, I don't have the tools to do a complete post mortem but I have a shop nearby that can help. I've had no problems with the mower for the several years I've used it. From the day I bought it, no knocking, banging or other symptoms except on the turn after a short pass it seemed a little sluggish. I thought something was jammed up underneath like a clod of grass or what-not and I gave it a few thumps when I passed over the sidewalk. At the end of the next turn, things went pear-shaped. The engine let go of a great deal of grey smoke along with a stink I can still smell a couple of weeks later. After that…nothing. I wasn't sure at first what happened but I thought something piston-related was the culprit.

    At first I didn't notice the shrapnel on the mower deck, and as I looked a little closer the side of the engine was blown out. I started by taking off as many bolt-on components that I had tools to do so to get a better look at the situation. When I took the head off, the valves and piston face looked perfect. No cracks or evidence of anything bent, no scarring, burning or galling…nothing. When I looked through the hole in the side, that's when I realized something went horribly wrong. The connecting rod was free and as I pushed the piston toward the head I saw what happened.

    I wonder if Briggs' engineers are aware of this problem. Could this be a casting problem at the foundry? Never, in my 40-or-so years of mowing grass have I seen a failure of this magnitude. Sure, a cracked piston, bent valves, contaminated fuel but never an engine blowing itself apart. Needless to say, I'm $300 down for a replacement but you've shown me a way to create a backup if I need one. Thank You.

  8. I don't understand why you went to all that effort. Around here I can just drive up to the scrapyard and pick through a few until I find a decent one. $20 later I have a nother mower.

  9. Those rods are piece of crap. They should make them from stronger material. I bought a mower withblown rod but deck of mower was excellent. had an upper/lower body. Took crankshaft and piston from bad engine. Need to order a connecting rod. You must of took good care of your mower to last 21yrs. Donot have control on when your gonnablow a rod.

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