Rebuilding a blown up Briggs Quantum Engine [Part 1]



This is a 3-part video on my friend and I repairing our first blown engine. We got it for free from our school’s automotive program because it didn’t run. I can’t guarantee everything we did was correct or to standard, but the engine is now running very nicely. You can see that in Part 3.
Part 1: Now Watching
Part 2: https://www.youtube.com/watch?v=KEWP8xYGr5A
Part 3: https://www.youtube.com/watch?v=mrejFn7nv1c
Our diagnosis was that the engine had a broken connecting rod because when cranking the engine, the piston did not move. Upon tearing it apart we confirmed that, and had to decide whether or not it was reasonable to fix it, due to the damage and cost of repairing it. The connecting rod wasn’t too badly damaged, and the end of the cylinder wall had a slight ding. Other than that the engine was very clean and appeared to have a fairly low amount of hours on it, so we decided to buy a connecting rod and sump cover gasket and attempt to fix it. Everything went pretty well, until upon starting the engine we realized that the governor system was not controlling the engine speed. Eventually I remembered to check the adjustment at the governor arm. We speculated that this unadjusted linkage may have cause the engine failure because the RPM’s were not being limited. After adjusting that, the engine ran great on its own. We also found that after testing the pump, it had a bad unloader valve, so the pump needed work as well.

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29 thoughts on “Rebuilding a blown up Briggs Quantum Engine [Part 1]

  1. How did you get the blade shaft out? I have a techumesh lawn mower engine and just can't get the sump plate off because of the blade shaft?

  2. i have one of these engines on a pressure washer. the pump has failed twice but the engine runs great, the damn thing is almost 20 years old. anyone says briggs is junk doesnt know anything……. of course maybe the newer models are junk because the quantum is an old design. not sure if its still in production in some form

  3. My neighbour has a "Mums: Ja #198544#" lawnmower. I guess it was hardly used coz the bearings, the cylinder and the rings are all OK except the exhaust valve came loose. As it turned out its guide, that looks like an insert, crumbled to several bits.Poor old b…d is very disappointed and I'm trying to help him but no idea. Any suggestion?

  4. I wouldn't reuse any of the parts that were exposed to the "pinball machine" that the crankcase became.   Also, please use a tripod.  Otherwise, I get vertigo looking at the handheld video.  Very interesting video.

  5. another YT video claims that the aluminum stuck to the hardened crank from the connecting rod can be taken off using lye such as in oven cleaner. ( dollar store?) Just use skin and eye protection.. I think I'd also try a brass wire brush, but idk what the lye does to that.. According to one blog, some brushes are steel wire that's coated with a copper or a bronze coating. I would also check that using a magnet.

  6. That engine looks brand new, I'm guessing someone bought that mower from a big box store in the box!  The customer failed to add oil, started it up, and it lasted for only a few minutes.

  7. At least the quantum engines are much better than the inferior professional series engines the governer gear is plastic and the camshaft is a polymer cam accoriding to B&S history it said the quantum is Briggs and stratton's first CAD designed engine and was released in 1986 30 years ago and is still available today just with different coverings, but the block is the same design but had different carburetors first started off with a manual choke carburetor, their flojet carburetor then in the 1990s the carburetor with the primer bulb was added and is still available and in the mid 2000s the engine got a Ready Start system a thermostatically controlled choke and air vane to open the choke. As the quantum engine i would still get today. but for the professional series engines i would stay away from they have a bunch of PLASTIC on it and inside it the camshaft and timing gears are plastic. the Quantum i will still recommend as the other newer B&S engines and professional series are Junk as the Quantum and the Vanguard series engines are the only good engines as well as the larger engines for riding and zero turn mowers are the only ones worth buying

  8. Does these junk Chinese engines now have plastic camshafts? There is no telling how much more crap they put in there that you don't see. America has gotten pathetic.

  9. ur camera bouncing around like that made me puke 3mins into the video had to stop watching,really wanted to finish it

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