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rustyj14

B&S lawn mower engines:

rustyj14
12 years ago

Several questions for the learned ones, about the subject line. (A vertical shaft engine.)

First: What makes the sump gasket blow out, even when the bolts are tight?

Could a blocked crank-case breather and tube be a factor?

Or: Could old age be the cause? (App. 10 years)

If the engine sets level all of the time, could crank-case pressure make oil come out past the upper crank-shaft seal? Would the breather have to be blocked by debris or dirt, etc.? Note: I had changed the oil the first time it came in, not the second time.


This mower sat in the shop, after the owner brought it back. He left it, and i sat and watched the oil run out of it, onto the mower deck. I had installed a new oil fill tube gasket. Not a used one--no--i bought it new. The oil fill tube is held in and down by a small hex-head screw.

Any ideas about this perplexing problem?

Also, if anybody needs rain, just come to W. PA. We have lots of it here!

Comments (6)

  • mownie
    12 years ago

    I posted "my opinion" on this relatively common problem some time back.
    My opinion is that Briggs does not design in enough "dowel pins" into the gasket surface perimeter of the sump cover to handle the transfer of reactive torque load between the sump cover and the crankcase during operation.
    Because the sump cover is also the engine mounting facility on the vertical engines........all torsion of the engine is counter acted by the crankshaft forces by being transferred to the sump cover and then to the frame/chassis.
    Briggs uses only 2 dowels, which effectively means that the rest of the loading is transferred through the sump cover bolts AND the gasket itself.
    Over time, the bolts relax their clamping force and this permits the sump gasket to lose adhesion to the surfaces of the sump cover and/or crankcase.
    Perhaps if Briggs designed in 2 more dowel pins at mid points between the 2 already there, the problem would stop.

  • briggsgalaxieman
    12 years ago

    I have some experience with blown out or leaking sump gaskets on vertical shaft Intek engines. Even if the bolts are tight, the gasket may not be in place. Factory assembly may not have placed the gasket properly to begin with. On vertical shaft engines (mine is: 446777) the sump to engine mating surface has two pins that are used to position the gasket during assembly. The pins are both near the 'bottom' of the engine where they positivly position the gasket. But, the gasket has no sure way of being held in place on the 'top' when the sump is assembled. Since no sealer is use other than the dry gasket, there is certainly a possibility that the gasket will slip out or not be positioned optimally once assembled. I lived with a sump gasket leak for many years before finally deciding to replace it. Here are two pictures of how the gasket and mating surface looked when disassembled:

    Note that where there are pins to hold the gasket, everything is fine, but where there are no pins...the gasket is gone...

    {{gwi:315047}}

    {{gwi:315045}}

  • rustyj14
    Original Author
    12 years ago

    Thanks, Mownie, and Galaxieman! I haven't ever seen that gasket leaking on lawn mower engines before this one, only on the lawn tractor engines, of which i have replaced a few over time.
    So, i think i'll give it a go, as the Brits say! Nothing to do here lately, except get a front fender ready for our '95 Buick. Yes, a '95! We don't use it much, sits more than driven. Wife grumping about the rusty look. I think all cars in PA. should be painted "rust brown"! It'd save a lot of wasted time! Bought a gallon of acrylic laquer thinner today, several sheets of wet or dry, a cup gasket, and parted with $64! WOO-HOO! Prices have gone way up. Thanks for the info. Rusty J.

  • rcmoser
    12 years ago

    Might try this? I super glue the gaskets in place on one side on any gasket I install. Haven't had one slide out yet. Use to do this on SBC engine that had solid lifters. Course the solid lifters and 8500 RPMs you had to adjust them quit often. The glue or RTV on one side would hold the gasket in place and could be used over several time with out leaking if you used inch pound torque wrench torguing the valve cover bolts. I think you all know my feelings using inch instead of foot for anything less than 16 foot pounds or 200 inch pounds.

  • andyma_gw
    12 years ago

    the real old school way was to put down a layer of heavy grease to stick the gasket. That way you had a prayer of re-using the gasket. I use Permatex 2 B Aviation Forma-gasket for this. You have to wait for it to skim over to get tacky. Just running some sewing thread through an opposing bolt hole works too.

  • rustyj14
    Original Author
    12 years ago

    I can't see any place where the gasket has slid out, or broken, although it is possible that it has. I may get into it later on, when the spring rush is over.
    Right now, we're having a glorious rain storm, with lightning and wind, trees and branches down, wires down, fire companies out for blocked roads, etc. While i sit and listen to the Fire Co. pager. I don't go out on calls any more-BT/DT! Only report for radio work in case of dire emergencies. At 86, i'm too old to go chasing fire trucks! During the day, in the shop, i'm busier than a one-armed paper hanger, with poison ivy!

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