Small engine bearings

Discussion in 'Mechanic and Repair' started by sevendavid5, Jul 20, 2019.

  1. sevendavid5

    sevendavid5 LawnSite Member
    Messages: 22

    Question for the small engine mechanics out there.

    Have most of the small engine manufacturers gone over to to bushings or sleeve bearing at the crank and flywheel side of the v twin engines?

    Also what does it mean when you are looking at engine specs and under bearings it says, "Bearings: parent material, plain, etc?" Many mfg's don't reference anything at all under bearings.

    One would think that the side load on any driven shaft that didn't have ball bearings under such heavy load would be way too much to last. Maybe most of the commercial engines come standard with them?

    I noticed the Honda V-twin engines say ball bearings.
  2. BigFish

    BigFish LawnSite Fanatic
    Messages: 5,425

    Actually, they've pretty much always been plain/sleeve brings, mostly on the flywheel side. Ball brings are not that common on mower motors. Obviously, some use ball brings, most don't. $$$
    Parent material pretty much means just the alum. Case/cover/sump.
    They don't reference bearings 'cause most don't use/have any.
    Auto motors don't use ball brings. and they handle tremendous loading, right?
    hort101 and flintknapper like this.
  3. OP

    sevendavid5 LawnSite Member
    Messages: 22

    Gotcha, makes sense and thank you for the reply. Auto engine sleeve bearings are also pressurized to run on a thin film of oil. So when small engines specify that they are pressurized, does that then mean full pressurization like an automobile engine or some half baked compromise that sounds good but really just filters and squirts oil on some moving parts.

    One reason that I am asking is that certain equipment have a stub shaft on the flywheel which in addition to the crank is also under considerable side load from say the hydraulic drive tensioner, etc. I am just thinking that this would cause premature or excessive wear on a non pressurized bearing or non ball/roller bearing and thus be less than ideal from a failure point of view?

    Just wondering if this specific issue of wear, such as wallowing of sleeve bearings, oil seals comes up often with engines that have this increased side load present?
    hort101 likes this.
  4. BigFish

    BigFish LawnSite Fanatic
    Messages: 5,425

    "Pressurized" u systems usually pump to flywhl brng, then thru crank to rods. Some pump up hyd. lifters. Lotta splash lubrication with any system, right.
    Most all svc manuals have an oil flow diagram. Find some links on here, then check them out.
    hort101 likes this.

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