Blown motor ?

Discussion in 'Mechanic and Repair' started by Bunton Guy, Oct 29, 2001.

  1. Bunton Guy

    Bunton Guy LawnSite Bronze Member
    Messages: 1,925

    I see alot of ads in the classifieds of all sorts with mowers with blown motors. What can these people possible do to blow the motors ? is this from a lack of maintnence & abusing it ?or is this normal problems ? what usually breaks when the engines " blow" is the usual case a rod that lets go ? or a crank that cracks ? or maybe piston sticking/seizing?
  2. John DiMartino

    John DiMartino LawnSite Silver Member
    Messages: 2,555

    If most of these have blown motors,I feel the rest of the machine is shot too,or else they would have invested the money to fix them.I only buy them when they are so cheap,that i can use them for parts.I see a seroius lack of maintance everytime i look at what is on LCO's trailers,golf courses typically take much better care of equipment,and it usually lasts a lot longer IMO.
  3. Fish

    Fish LawnSite Member
    Messages: 139

    Blown motor is a widely used and abused term, and means
    little until the engine has been inspected. If a mower starts
    smoking badly, people might trash it, not knowing the problem
    could be a flooding carb, or blown head gasket{OHV}. I
    stopped by the local hardware store and the mechanic was
    uncrating a new Briggs twin shortblock, saying that is was
    for this one tractor that was not even torn down at all.
    I ask him why, he said the rod was knocking very badly. I told
    him a chunk of carbon can do the same thing, it has fooled
    me before. The next week I came by and the customer had his
    mower back, with a new shortblock, and the mechanic had a used shortblock for sale. Oddly, he never did find out why it
    was knocking[wink]. "The rods looked good", was all he said.
    So a motor that is "blown", may be not so bad. And you
    may buy something that is a good deal.
  4. Bunton Guy

    Bunton Guy LawnSite Bronze Member
    Messages: 1,925

    The term "Short blocking " is that refering to taking the block off another mower to use it on your ? or is because the block is really shorter ? please enlighten me. I hear that term very often to:blush:
  5. justractors

    justractors LawnSite Member
    Messages: 39

    After 35 years of working in small engine repair related fields, in my humble opinion, most small engine damage is caused by lack proper preventative maintenance.

    The most overlooked item on these engines is the engine oil level. I continually see engines brought in with broken rods, scored cylinders, oil saturated air filters, and massive oil leaks caused by either too little or too much oil. Too oftem operators fail to check the oil level causing too little oil or check the oil level, find it at or below the add mark, forget the engine holds less than a quart, and add a quart. Overfilling the crankcase on most small engines causes faoming and oil saturated with air adds very little lubrication. Overfilling also causes oil to be forced into the air filter and through gaslets and seals.

    The second most overlooked preventative maintenance item is the air filtration system. Most of these engines use filters which are marginal at best and if the air filters are not properly cleaned and installed costly problems will happen. Many engines that are brought to me and are "burning a lot of oil" have air filters that a plugged up. If the engine is running it is sucking air from somewhere and if the air filter is nearly plugged the engine may be getting it's air through the engine by way of the crankcase breather. The air filter must be properly installed to insure all the air coming into the engine is being cleaned by the air filter. It takes very little dirt in a small engine to cause major damage.

    Other items that cause damage in lesser degrees are dirty fuel, failing to let the engine warm up and cool down properly (many blown head gaskets are caused this way), wrong spark plugs (moslly in two cyle application, improperly mixed two cycle oil, wrong type of oil or fule, and equipment abuse.

    Again these are just my opinions.

    Thanks for your time, Bill
  6. Fish

    Fish LawnSite Member
    Messages: 139

    A shortblock is the core of an engine, it is replaced and the starter
    carb, muffler, coil, etc, is transferred from the old engine to the
    new one, which can have problems by itself. A "longblock"
    is a complete engine that is bolted on, hooked up, and ready to
  7. justractors

    justractors LawnSite Member
    Messages: 39

    In the small engine area the two items normally found are short blocks and complete engines
    In the automotive end of it there are short blocks which are blocks with crank, rods, piston and rings, camshaft with lifters, timing chain/gears, and gaskets.
    Long blocks are the above with heads installed, push rods, and timing cover gaskets.
  8. Fish

    Fish LawnSite Member
    Messages: 139

    You are correct. I do not work on cars, but was trying to use
    that terminology, which I failed. I do not work on cars, so I defer
    to your take on the matter.
  9. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    I agre with Justractors. I find that most major engine problems are from a high build up of chaff in the cooling fins and very dirty motor oil. I find this abuse on residential mowers more than commercial. But there are exceptions out there.
  10. mczajka

    mczajka LawnSite Member
    Messages: 1

    I appreciate all of your comments above - I am one of the losers that could not properly read the oil level in my mower. Although I did periodically fill it with oil, it obviously was not enough. This weekend I encountered some very thick grass, and because I was trying to do the final low cut for the season, the engine started smoking, and then the engine started to make a loud knocking noise. I immediately turned it off, checked the oil, which of course was very low. I filled the oil level to the proper setting.

    So the problem is - it runs, but knocks loudly. Is this repairable or not worth the expense?

    Thanks for your comments.

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