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: • Rebuilding a blown up ...
Part 3: • Rebuilding a blown up ...
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.

[@luckydog-287]

"Great job. Better demonstration not possible. Thx" Also, what classic engine to do a video on. Great work!

[@MrShobar]

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.

[@glennspeeds]

Be sure you get the proper thickness sump cover gasket so you will have the correct crankshaft end play

[@mckinzi1]

hope you've learned by now the piston comes out thru the top not the crankcase. may not make a difference but if the book says install into top of cylinder you can bet that's the way it's supposed to come out. usually you have to clean the ridge of carbon at the top by the head. that can damage your piston as you remove it. lower piston and clean the ridge and yank the piston out. quantums are fun.

[@mckinzi1]

if you can't polish the scratches off the rod journal of the crank it will blow up again. and it is a good idea to pull the flywheel before you break apart the engine. the crank and flywheel flopping about will tear up your 40 dollar magneto.

[@christophchamberlain8025]

Lol that crank is shot there a big dent in it if he uses that it will blow apart for sure

[@simonilett998]

The 'keyway' is the slot in the shaft and flywheel. The small rectagular piece of metal is the 'key', and aligns the two 'keyways'.🤣👍

[@derekobidowski7574]

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

[@polymexdf69]

I didnt pay attention when i took mine apart on Tappet-Valves sowhat is the diferecne what could hapened if i put them in the wrong spot because after putting everytnig back my engine wont star before i close engine case i make sure that everything turn freelly and it did i wasnt sure about the governor but I aligned the gears where the marks where help please thanks

[@raulagustinrichotti3172]

Motor 3.5 Biggs. Stratton

[@SalehSaleh-ts4xu]

thanks

[@MrBugsier5]

at the end of the video, watch te alignment of the piston springs, there not turned!

[@nigelfreeman1]

What is a piston spring?

[@sibalogh]

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?

[@Stillstoned1]

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.

[@fdamien80]

superhoggbike Plastic camshaft, governor have been used for decades and are known to last for years if property maintained.

[@daphantom1173]

It is not a plastic camshaft, it is a steel camshaft with a nylon timing gear. Many Motor vehicle engines were made with composite timing gears - eg. early Volkswagons, Holden and others. In later production they were changed for Aluminium. It is good practice to coat the camshaft cams and the base of the cam followers with Moly grease during assembly.

[@fleetwin1]

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.

[@philiphartley8823]

" I think I need a new sump Gasket" has to be the quote of the month.

[@theonewheelednavy3854]

The rubbing alcohol smell means that some one ran sea foam through it to clean out the carb, and didn't change the oil

[@MrMacman98]

Personally, I would have replaced that crank, those marks in it are from the rod self-destructing

[@ryanrohauer5940]

RIGHT at least polish off all that aluminum. lol he goes oh its barley even scorn lol

[@LawnMowersThingsThatMakeNoise]

i summise the engine was hydrolocked while running and it snapped that rod

[@ELPaso1990TX]

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?

[@bigredjeep40]

Was the flywheel already that loose? Didn't need a puller?

[@andysmith1531]

Does it bug anyone else when people refer to the key as a key way? Lol

[@harrisb43]

Drives me nuts! I have watched dozens of videos from guys at all skill levels and have never heard one make the correct reference.

[@colstace2560]

It is funny, the key fits in the key way, how do so many ppl get it wrong ??

[@kierankay100]

you cannot check a scored cylinder by looking through the back at the top of the cylinder it is usually scored next to the valves or the bottom of the cylinder Good video i have never seen inside a quantum engine before

[@mowerrepairshopfortscottkansas]

I Have been rebuilding small engines for 15 years and you have done a grate job on this video.

[@simonilett998]

*great*

[@ryanmcgouirk2655]

Good video I work for Briggs I am rebuilding to 12 HP power built motors

[@jimdavidson5208]

You're supposed to remove the spark plug wire FIRST. My God, you could of killed us all LOL.

[@tfoen7678]

I remember they use to teach this in high school; small engines, automotive tech, industrial design when I was in high school. Too bad they don't teach it anymore but online.

[@seabass22]

Tien Foen no money to be made, when teaching people stuff they can actually use in life.

[@LawnMowersThingsThatMakeNoise]

its a "Key" that slots into the "Key Way" never pull the piston out of the crank side of the bore. take it out the top

[@eugeneoreilly9356]

Don't you just love those plastic cam gears.Plastic crankshafts probably next.

[@ad356]

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

[@juliolausell4399]

+andrew donohue I agree with you. I have a briggs riding lawnmower 12.5 ohv. It has about 2500 cutting grass hours on it. 18years of work. It does have little noises coming from the inside, but it just won't give-up. Its never been apart. I fill the oil level past full, ABOUT 2/3rds more oil than it should have. Most people say NO!!!!!!! you can't do that, I say 2500 working hrs, It's that simple. BRIGGS & THE LITTLE ENGINE THAT STILL CAN. LOL.

[@AdrianWilliams-h6o]

I think the Italians make good pressure washer pumps. Get the right pump and engine combo happy days

[@zinnstigertownmowers780]

Looked like gas got into your oil. That's a cheap pressure washe engien I'd replace it

[@labananiere]

Vu l'état de ce moteur qui me semble pas très vieux, je présume qu'il a fonctionné sans huile. Réparation sans doute plus chère qu'un moteur neuf.

[@paulettacox6893]

Where you from.. Dan the man

[@pkf4124]

Thatll buff right out

[@iridekawi5]

its nice to see somone rebuild these rather than it laying in some scrap pile

[@1001awab]

Great job. Better demonstration not possible. Thx

[@RichardsWorld]

If that was a car, we would call that crank shaft fucked up. But I notice small engines let you get away with some loose specs. You could take it to a machine shop. It probably wouldn't cost much because they would only have to grind one journal. But then you would have to order the proper rod bearings.

[@conner5611]

These dont use rod bearings just a rod and cap

[@raulagustinrichotti3172]

Puesta a punto del motor Biggs. Stratton 3.5.

[@dreafrank]

You could use a strap wrench around the flywheel to stabilize it when remvoing the flywheel cup and nut.

[@philiphartley8823]

This engine looks quite new, non of the usual wear related marks.

[@DonovanBryant92]

i am using one of these for a go kart that im building and im trying to find a steel camshaft so the engine wont self destruct while im driving the go kart

[@MK14Monkey]

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

[@Venturi2012]

MK14Monkey Sounds like me on a boat ride I went on years ago. I made it about 20 minutes in before I puked over the side, so I know the feeling. Sounds like you have it worse than me though, don't worry that sickness feeling goes away by the next day.

[@christophchamberlain8025]

That crank is spent come on bro realy good luck brother

[@1Jomarcel]

Why plastic gear run with metal gear

[@sidewaysaction9983]

"never use as pry bar or chisel" spring to mind, claw hammer!!!!!

[@ad356]

this is also a pressure washer engine, isnt it?

[@mrodriguez5259]

Magnific 👍

[@slimjim119]

looks like it locked up

[@mitchroegiest6405]

connecting rod bearing nowhere to be found lol

[@tuckercole1531]

Mitch Roegiest they don’t have a rod bearing

[@theDugonator]

How did you manage to break the connecting rod on a lawnmower?

[@martincastillo929]

JDM street racing

[@demigod217]

lmao

[@scgamer2442]

that govener is also the oil slinger.

[@meyawabdulaziz3863]

are these plastic parts in there ?

[@Venturi2012]

Yes, nylon. The cam and governor gear is.

[@meyawabdulaziz3863]

:O....noooo seriously ? can you have those made from metal or something ?

[@scdevon]

Faisal Abdulaziz They've been using nylon parts for a very long time now. Like 20+ years. Tecumseh did too when they were still in business. Honda has been using nylon cams for at least 20 years in their small engines. I don't like it either, but they do seem to hold up well.

[@ad356]

+scdevon i think its more to reduce noise then anything.

[@meyawabdulaziz3863]

andrew donohue hmmm

[@awyeh1234]

Omg this is why I hate Briggs, how the hell can an engine last a long time with a plastic cam?

[@theonewheelednavy3854]

awyeh1234 many new mowers us plastic, even in the transition now

[@user-te6rb5to8c]

Honda does the same thing. Even worse is they replaced the gear on the crank with plastic.

[@awyeh1234]

. Hmm didn't know that, I mean the newest engine I've worked on from Honda was a 2010 so maybe they transferred to that more recently

[@lawnmowerdude]

Notice how the plastic cam isn't what broke...

[@ryanrohauer5940]

low valve spring pressure. these small engines don't endure the amount of stress a car engine does. also briggs makes good engines its the dealer that cheaps out on engine options. residential motors are generally plastic, cam gear and starter ring the commercial stuff use steel and iron sleeves. plastic in a bone stock engine is no biggie most of em break rods or drop valve seat before the cam get breaks tho it happens but rarely. and theres no metalon metal wear keeps oil cleaner and less metal flying around that engine but ill be the first to jump on the breaks and scatters band wagon lol (honda guy)

[@martincastillo929]

ur not supposed to touch the bearings

[@duettatraktor7949]

+Martin Castillo Wat do you mean? Dont touch the bearings?

[@LW65PL]

Silniki Briggsa to totalne gówno. Obecnie chińskie silniki są dużo lepsze a o wiele tańsze

[@Trijem235]

Thanks for the video!! I really appreciated it.

[@stankdog1357]

your dad has nice tools

[@frankdiesel1288]

I also have a small engine repair shop and Harbor Freight sells those engines new for around $125.00

[@jimdavidson5208]

+Sam Jones HF sells Chinese engines. Not Briggs.

[@michaelreagan2232]

+Sam Jones Sam Do the H. Freight engines drop in as replacement? I am facing a rebuild on my lawnmower also

[@This0is0pointless]

technically its the same stuff, briggs even has assembly lines in china now so its all built there, damn shame

[@michaelreagan2232]

Followed the advice on here, bought a HB motor for $99 on super sale. bolted right on, runs great