Head gasket #3 - 16hp Briggs single in 912AC

[rickpilgrim 1]

Last week, 87 degrees outside, customer HAD to have lawn mowed with Simplicity only.

Mid afternoon crew calls " hey, the 912 lost power just now!"

Took it apart today and head gasket breached on flywheel side of piston end. Point gap perfect, 91ron fuel, 3400 rpm and this is the 3rd time since I've had this Briggs this has happened . Now I have battery ign with 12v to start and 9v running and the condenser is a sbc points one and am running an E3 spark plug could that be contributing to this?

At this point even though the glass and feeler gauge says maybe but not too bad I'm thinking of sending head to be milled flat. Of course that and detonation/knock/ping go hand and hand so......

I'd really like to save this motor, thoughts anyone?

[dentwizz 6]

I would definitely say it needs to be flatness checked and some new bolts torque checked carefully. In several instances over the years I have seen heads that needed periodic head torque checking until they settle in(or get milled, but people tend to not go that route for cheapness).

[rickpilgrim 1]

I've had this motor for over 10 yrs, first it came in a 3416H we ran for 3 seasons until the Vickers was getting tired, then in our 716 chassis where gasket 1 went out. New gasket and 5-6 yrs later the 716 was history as was gasket 2 so a fresh hone, new piston/rings/ con rod /valve guides and seals and gaskets and into the 912 which brings us to spring of 2014. Now it's gasket 3 so likely have the head milled and get an OE gasket and try again.

[720nut 4,225]

If this has been a reacurring problem I'ld have head and block both milled. Could be block is actually the problem

[BLT 718]

Chase the block threads down with a 5/16-24 bottoming tap to make sure you are getting correct torque.

[Ronald Hribar 105]

Flat piece of wood with sandpaper will quickly tell you if block or head is warped

And BLT is correct to chase the threads

[Multiplicity 0]

.

....Other than the advise already given, I've

repaired engines for years and almost always

find head bolts loose, whether it's shrinking

gaskets or just time....I never start any

repair w/o checking the torque of the head

bolts.....It would appear that they should be

inspected more often than most owners do....

.

[lugnard 73]

Copper head gaskets? Are they available for this motor? Might be worth a try.

Harry

[rickpilgrim 1]

Originally posted by Multiplicity

.....Other than the advise already given, I'verepaired engines for years and almost alwaysfind head bolts loose, whether it's shrinking gaskets or just time....I never start any repair w/o checking the torque of the head bolts.....It would appear that they should beinspected more often than most owners do.....Possible as bolts were not that loose but no more than 15ft/lb tight either.

[Hudco 0]

make sure you are not running to lean

[isetta 50]

Yes, too lean, too hot. Check throttle shaft / carb body for wear, lets in air, mixture too lean, overheats, detonates. My 912H Kohler ate up the top land on the piston from pre-ignition before I figured it out.

[rickpilgrim 1]

Definitely not on the lean side of the fuel curve, spark plug dark colored, light black soot over the head/piston/valves usually meaning slightly rich on mixture. Thanks for the future tips on the watch for list. We always run 91-93 octane pure fuel in our small engines.

[MDB 134]

One of the things that I have done with these engines that have head gasket issues is use a thin coating of aviation form a gasket, torque the head to specs., run the engine up to operating temperature and then retorque the head bolts. So far have had zero gasket failures with this process..

I have 2 model 19ds one in my B1 and 1 in my 725 that liked to eat head gaskets. had them both trued up and still would blow out till I used the permatex and hot torque trick. So far so good.....

[rickpilgrim 1]

Thanks, use the aviation form a gasket on 2 stroke crank cases and fuel related things but never tried it on head gaskets.

[Jr.lll 7]

On the retorque process, is this while the engine is hot or wait till the engine cools?

[jlasater 287]

New studs or bolts as well...they can stretch and never get stronger...

[kwt 302]

I can't imagine lean/hot/detonation being the problem. The flywheel side is the coolest part of the engine.

[Bill725 1,177]

B&S has changed the material used to make the head gaskets. The old P/N is 270662 and the new P/N is 692231.

I have in the past taken a sheet of fine emery paper and used double sided tape to stick it to a granite block to sand the mating surface flat. You could also use a piece of glass.

I also think new head bolts torqued to 190 in-lbs in the sequence shown in the service manual, along with an old style head gasket would be my next step.