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Follow-up on lawn mower with bad spark-plug threads

Discussion in 'Electronic Repair' started by meirman, Jan 22, 2005.

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  1. meirman

    meirman Guest

    Follow-up on the engine with bad spark-plug threads that you were good
    enough to advice me on a couple months ago .

    The hole was definitely too small for the bigger sparkplugs, so I
    decided to go with the helicoil.

    The motorcycle shop was willing to do it for 6 dollars for the
    helicoil and iirc 30 dollars installation.

    Also, on E-bay, I found a lower cost brand, Recoil Fix-a-thred (no a),
    and the vendor said it was better because the insertion tool was metal
    instead of plastic. And he said that the coils themselves were the
    same as the other brand used. Helicoil brand? I think his buy-it-now
    price was about 40 dollars and I was willing to spend the extra to
    have the tool. (not sure about the price. I don't see them for sale
    now, and ebay purged my Watch list of the old items (probably because
    they purge completed auctions after 30 or 60 days or something.)

    (although now I see a Helicoil brand kit for 12MM with less than 4
    hours to go (15:16PST on Saturday) whose current bid is 20.50 dollars
    plus 8 dollars shipping. This week there seems to be a lot of
    helicoil stuff, but not that one guy. Last time a lot of that one
    guy, but little else. :) )

    But I also took the head off the engine to clean inside and I noticed
    -- well I didn't notice enough and I'm very confused now -- that even
    though the spark plug fell out if placed in halfway and turned it, if
    I pushed it in all the way, there seemed to be good threads in the
    head at the very bottom (of the head, not the plug).

    I feel like a fool, and that I wasted your time. I apologize.
    Although I am glad to learn what I did about helicoils, and maybe
    telling you about the off-brand and ebay is enough to make up for
    wasting your time.

    Maybe sometime next summer I'll have to take the plug out for some
    reason, and I'll figure out why it was so hard for me to screw in.
    I've never had a problem before putting in a sparkplug and maybe I'm
    not such a fool, somehow.

  2. meirman

    meirman Guest

    In on Sat, 22 Jan 2005 15:03:43 -0500 meirman
    This was meant for another group, But I'm going
    to think that most guys who fix electronics also fix their lawn mowers
    when they need it.

  3. A fool for what? If some of the threads were damaged, a repair was still
    needed. It wouldn't be very cool for the spark plug to pop out (probably
    rather violently) half way through the lawn. :)

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  4. NSM

    NSM Guest

    If the threads are damaged, helicoil it. Don't rely on just some of the
    threads. I'd have paid the shop - seems like a fair price for one plug.

  5. BOB URZ

    BOB URZ Guest

    If its one of the garden variety BS with valves in the block, there
    is another solution. Every town has its shade tree mower shop.
    Yea, that's that one with mower parts stacked up all over the yard.

    Take the head off for comparison and get a used one off a donor. Then buy a
    new head gasket. I got a crank that way for a 3.5 BS.
    Bet you can get a used one for less than the repair kit if you hunt
    deep enough.

  6. James Sweet

    James Sweet Guest

    Yep, I started out fixing things with lawnmowers, remarkably simple and
    robust machines. In your case I would have replaced the cylinder head
    though, usually a mower shop will have a whole pile of scrapped stuff and
    would be happy to sell you a good used part.
  7. meirman

    meirman Guest

    In on Sat, 22 Jan 2005 21:16:46 GMT "James
    Thanks for the suggestion. This was a 6 or 6.5 HP Craftsman engine,
    and I don't think they've been making that for more than a few years
    (so they're still new), or selling that many. I don't think I could
    find one in the time I had available. (winter was coming.)

  8. meirman

    meirman Guest

    In on 22 Jan 2005 15:44:34 -0500 Sam Goldwasser
    Thank you for denying I'm a fool. But I know myself, and if it ran
    for 3 minutes, I'll try to run it for 20 next summer. (That's how long
    it takes to mow my lawn. And 20 for weedwacking.) So knowing how I
    am, I was either a fool for bothering you, or a fool for not trying
    harder to screw in the plug.

    I actually just screwed it in almost finger-tight the first time I
    started it, and it made one "blam" and stopped. The spark plug shot
    out about 6 inches, restrained I guess by the spark plug wire. Once
    the engine is really revving it will probably go farther, regardless
    of the wire, but the plug is on the far side of the mower, so I'm
    safe. And in practice, there is almost always no one around when I
    mow the lawn. Even when there is, they've always been on the other
    side of the picket fence and at least 10 or 20 feet away. Still, I
    don't want to risk anyone's knees, and I might want to walk in front
    of it when it's running, so I'll see how things go in the spring.

    I have a mower, but I saw this at an auto junk yard (one that seems to
    have more non-autos than any others I've been to), and he only wanted
    10 dollars. But I don't want to invest too much until I see how I
    like it, compared to the other one.

    Thanks a lot.

  9. meirman

    meirman Guest

    In on Sat, 22 Jan 2005 15:02:04 -0600 BOB URZ

    Well, I may do that yet, in the spring. Thanks.
    Thanks for the suggestions.

    I just don't know where to find a donor. I know about 5 repair shops,
    but the one nearest me is expensive (at least for used mowers) and,
    like I say, it's not a common engine, afaik.

    Not BS and and not small.

  10. James Sweet

    James Sweet Guest

    Craftsman doesn't make engines, it's probably made by Tecumseh, which while
    not as cross-compatible as Briggs & Stratton, it should still be easy to
    find a head that will fit.
  11. none

    none Guest

    The OP could try getting a helicoil to fix his original head.
    They can be gotten at NAPA or any good auto parts store.
    If his craftsman mower does have the tecumseh engine it should take a
    standard J19 plug, a fairly standard diameter and thread pitch.
    If you go the head replacement route it gonna cost you, unless you can
    find a junk engine that'll match. You will most likely have to buy a
    new head gasket as well as most late models use a cheap foil laminated
    paper gasket that's sure to come apart when you pull the old
    head.(earlier models had a heavy metal head gasket that lasted
    If on the other hand it's a B&S get ready to shell out for new parts
    as every engine they make is very parts specific and pricey.
  12. James Sweet

    James Sweet Guest

    Huh? I've been repairing B&S engines off and on for around 15 years now and
    have never run into this problem, I've used parts made in the early 70's on
    engines made in the late 80's and vice-versa, never had any problem at all
    finding good used or reasonably priced new parts for them, though I haven't
    worked on any that were newer than early 90's, they generally don't need
    more than basic tuneup parts.
  13. none

    none Guest

    If you're referring to their earlier model sprint engine or smaller
    3.5/4hp they're not too bad as long as you don't run them to hard.
    Anything past about 87 is pure crap. Especially their Quantum or
    larger OHV junk.
    Aluminum used in high stress parts such as valves and piston arms
    B&S is also good about changing tolerances in mid production to ensure
    aftermarket parts jobbers suffer, not to mention how it can make the
    home repair owner's life hell.
    I could go on and on...
    I have a huge pile of B&S motors behind my shop(I do small engine
    Most suffered catastrophic engine failure do to cheap material and
    shoddy craftsmanship, some right out of the box.
    As for interchangability.... IF you can get a part to cross you're
    I've had experiences where internal parts from one model wouldn't fit
    an exact model of the following year or series.(Mostly piston arms/
    crankshaft tolerances.)
    B&S likes to vary the coil sizes as well. Techumseh's generally use
    one size coil.
    B&S likes to use a plethora of different length and style of control
    cables as well, both throttle and safety/cutoff cables.(AND charge and
    arm and a leg for them.)
    B&S also uses the worst carbuerators I've ever seen as well as the
    most ill concieved govenor system ever applied to small
    engines.(plastic carbs on their small engines that once they wear out
    that's it, just toss and replace. Even the more expensive engines use
    crappy Walbro carbs.)
    After just hours of use most B&S engines suffer uneven engine idle as
    the govenor system can't adjust for engine runout.
    I have some Techumseh engines that have been going for years and
    hundreds of hours.( Steel alloy pistons and cast irons sleeves)
    You're lucky to get the rated hours out of a B&S.(FYI the small 3.5/4
    hp mower engines that Briggs makes are generally rated at 30-40 hrs of
    use. I have managed to get as much as 100 out of some of the older
    models but only after tweaking the govenors down and keeping fresh oil
    iin them at all times.)
    As for Briggs not needing service... I do a steady business on small
    engine repair and most of the dead lawn equipment that come into my
    shop have B&S motors.(Burned coils in the first year, engine
    explosions due to poor craftsmanship/tolerances etc...)
    I mostly swap them for a tecumseh engine and have happy customers
    It could be said that at one time Briggs did make a quality engine,
    however that's simpl not true anymore.(I DO have some vintage Briggs
    from the early 60's and as late as the late 70's that are very fine
    engines and put Brigg's later offerings to shame both in reliability
    and power.)
  14. James Sweet

    James Sweet Guest

    Dang have they really gone that far downhill? I've had nothing but excellent
    performance out of B&S engines, I particularly like the 80's-early 90's I/C
    flatheads with the cast iron bore, maybe I've just been lucky but I've just
    never had anything major go wrong with any of them and the carburetors have
    been some of the easiest and most dependable I've ever dealt with. I've had
    too limited experience with the OHV stuff, encountered them a few times on
    pressure washers I've borrowed (and they worked well but were also fairly
    new) but I've never had to work on them.

    I've had exactly the opposite experience with Tecumseh, though I was never
    surprised because last I checked (about 10 years ago) they were always about
    $100 cheaper than a comparable size B&S. I've had several of them throw
    rods, ignition go wonky, carburetors that wouldn't stay in tune and would
    clog up every time they sat a few months, hard starting, rough idle, and it
    always seemed like they were unnessesarily hard to take apart for simple
    stuff (head bolts holding the cowling on?!). They were the one brand I swore
    off ever buying.

    Guess I better hoard the few old (mostly late 70's-early 80's) B&S engines I
  15. none

    none Guest

    Actually, the only way to get a B&S that's built for durability is to
    pay through the nose, usually somewhere in the range of 500 bucks or
    more, whereas Techumseh are all built rugged.
    Briggs is so bad about making so many different versions of the same
    model engine that most all that are in the lawn care business and have
    any savy run from them.
    If you take apart those 80's/90's models of Briggs you mentioned
    you'll find alot of copycat design in them. Take the starter recoil
    mechanics and shroud for instance. A direct copy of Tecumseh's far
    superior starter recoils, except they're built with far too much
    plastic to hold up for long.(what's especially bad is the use of
    PLASTIC pawls instead of steel. You'll only see the steel pawls in the
    top end commercial Briggs motors, whereas ALL Tecumseh starter
    assemblies use stainless steel pawls.)
    Briggs is especially bad about using very cheap steel in the recoil
    springs, which results in some pretty bad jams once the starters have
    seen a bit of wear. Once the spring folds up and jams the whole
    assembly it usually takes everything else as well as the pawls will
    stick in the extended position.
    You can't be serious about Walbro making a good carb, considered the
    worst in the business.( That from my 30 some odd years working int he
    Briggs is also famous for having some of the worst electronics in the
    ignition system. Coils that can fry out after just a few hours.(I
    NEVER replace them with oem on any of my customers machines.
    I've had better luck with Stens aftermarket than original Briggs.)
    B&S, as I'd mentioned is bad about varying the size and values on
    their coils as well. It can be a real guessing game as to what size
    coil any particular model of a Briggs might take.(IMO this is
    completely uneccessary, they could easily make one size and value coil
    for all their single cylinder engines instead of the dozen or so they
    Even the OHV's they make for use on pressure washers are shabby.
    I have the service contract for a local rental companies fleet of
    pressure washers. Virtually all the one's with Briggs engines have had
    catastrophic engine failures(exploding engines usually from thrown
    rods and spun cranks.)
    We wound up replacing them with either Honda or Toyo engines, which
    sadly enough cost LESS than the cruder, simpler designed and built B&S
    In all my years I've never even heard of a Tecumseh engine having any
    internal failure, remarkable considering that you'll find them in alot
    of off road recreation equipment that get run very hard, even to the
    point of abuse.
    As for their ignition... All that could go wrong is the coil, and
    Tecumseh has the best track record for endurance in that regards.(I've
    even taken coils off engines that had been sitting in the parts bin
    for years and had them run on much later models with no problems.)
    Any carb can clog up if you let it sit long enough. the walbro's are
    worse for that in my opinion.
    As for rough idle, you can't be serious? The only way to get any kind
    of faulty idle on a Tecumseh carb is if you try and run them with a
    rotted primer bulb or dirty gas.(Tecumseh uses a counterbalanced
    govenor system that literally makes for a rock steady idle, unlike
    Briggs which are famous for up and down idle states.)

    That said, ask yourself how many hours on a given day you actually run
    your briggs engine. If you just cut your own yard at most an hour? And
    what one a week tops?
    Remember when I told you about the actual ratings that Briggs gives
    for expected engine life for their engines? On consumer models at best
    50 hours.(pathetic really)
    And yes IF you really take care of them you can get more, most owners
    don't though which is where I get SO much business.( most scoff at the
    thought of changing the oil at least every two use cycles which is
    paramount for keeping an engine clean.)
    I have customers in the lawn care business that on a usual day will
    run their Tecumseh engines for as long as 7-8 hours, some even more.
    On average they'll get as much as 5 seasons out of them, your'e lucky
    to get one out of a B&S at that level of work load.
    Many of my customers use commercial duty Snappers which almost always
    come with Briggs engines and which crap out the first year.
    I replace them with a comparable Tecumseh and will seldom see them
    come back for service for as much as three years, then it's usually a
    tune up and replacement of the primer bulb.
    I have several old Craftsman mowers that i keep around for loaners on
    warranty work, all run Tecumseh and the oldest one is from the early
    80's and still going strong.
    Yeah, as anything later will dissapoint you.
    As I said I have a huge pile of junk Briggs behind the shop.(once or
    twice a year it means a trip to the scrap yard just to get rid of
  16. James Sweet

    James Sweet Guest

    I don't know if they were made by Walbro or someone else, the ones I'm
    referring to are the aluminum Pulse-Jet carbs, only one needle valve to
    adjust, I've just never come across one that was much trouble.

    I guess things must have changed, I've never run into that problem, I
    particularly like the Magnetron electronic ignition, have that on a couple
    motors (one of which replaced a Tecumseh that threw a rod on a tiller) and
    it runs MUCH better than the old motor ever did, granted the old one was
    from the 70s.

    Honda also makes a very good engine, though I've found them a little tougher
    to work on, but again very good.
    I had the one with the thrown rod around for a while because I fixed it by
    epoxing up the hole in the crankcase and replacing the rod, but it never did
    idle very well, the carb would clog and finally the ignition coil failed so
    I junked it.
    Yes I'm serious, I'm beginning to think we might live on different planets
    though, or perhaps the climate difference accounts for this?
    Primer bulb always seemed silly to me, I've had a couple of them rot out, as
    far as I know they're the only common 4 stroke that needs one.

    50 hours is pretty bad, I know my mower must have many times more though,
    it's at least 20 years old and has had a lot of use, engine still runs
    strong though. I change the oil every year though, I doubt most people do

    Sounds like perhaps things have changed though, so much has, noticed the
    Fluke meter we have at work felt a little lighter than my own and the switch
    is a little sloppy and not as solid feeling, flipped it over and it's made
    in China! Usually that wouldn't surprise me but this is a *Fluke*! If I
    wanted a Chinese multimeter I'd go buy one at Fry's for $25. Fluke is top of
    the line and can command the much higher price due to a reputation of top
    quality and being US-made.
  17. Bob Shuman

    Bob Shuman Guest

    Experience w/ Techumseh and B&S so noted, but cut for brevity...
    I am surprised by the B&S 50 hour life rating. Can you cite a reference for
    this number?
    Can you please clarify what is meant by "use cycle" above. IIRC, my Honda
    lawnmower engine user manual stated that under normal homeowner use (every 4
    days for 1 hour for me from Spring through Fall) the engine oil was to be
    changed after the 1st hour of use and then after every 25 hours. I'm just
    not sure what a "use cycle" means in terms of cumulative hours of operation.

    Thanks in advance for the response.
  18. none

    none Guest

    Just check any of the specs in the parts manuals on replacement
    engines. They'll give a max hour rating for warranty purposes,
    something the salesman at the parts counter doesn't want you to see.
    After all 200-500 bucks for a engine that if run for 1-2 days non-stop
    is past it's warranty.
    If you stop and think about the time it actually takes you to cut the
    average size yard with a walk behind mower it's what an hour at the
    And the average homeowner cut their yard around 6-7 times during the
    average summer. This would give you about 3-4 years on the engine
    warranty. Heck most homeowners toss their mowers off after one
    summer's use.( They'll push it under the edge of the house or worse
    yet just park it in the corner of the back yard leaving it exposed to
    the elements. Worse yet they leave gas in it over the winter, then
    expect it to start first pull in the spring. Bad gas, soupy, burnt oil
    and a dirty plug anf they're suprised when it doesn't start.)
    I can drive around in early spring and pick up mowers off the street
    where homeowners put them out with the trash, simply because the
    failed to take proper care of them over the winter months and are
    either too stupid or lazy to do the required service to get them going
    again.( Not to mention too damn cheap to pay a service shop even as
    little as 20 bucks for a tune up.)
    Yet they'll toss it out and go and plop down another 190-300 bucks on
    a new one, which of course will be tossed out in a years time as well.

    Lawn care professionals know about the very limited time warranty on
    engines today and choose the brand and models that'll give them the
    best value.
    Once upon a time virtually all the pro grade snappers came with a
    commercial Briggs engine. Not true anymore. just go by your local
    commercial lawnmower supply shop and you'll see the top of the line
    Snappers usually have Tecumseh. They only offer B&S on some to sell to
    those who are loyal Briggs fans.( I started out many moons ago as a
    B&S fan when I started cutting yards in my youth, and stayed loyal
    untill just the past decade or so. After enough years being trained in
    engine repair and even more working on them brand loyalty WILL take a
    back seat to plain facts. There was atime when like many I saw
    Tecumseh's as being cheap in construction. The roles have been
    reversed though, just look at all the Craftsman brand mowers that'r
    still going strong after years of use.)
    A use cycle is one cutting.(Time of engine operation is just one
    factor to consider in wear. The real damage to the oil occurs AFTER
    you turn the engine off. All the trapped gas vapors condense down into
    the oil pan and break the oil down, which is why it better to change
    the oil before each use, not after.)
    I change the oil in my home mower before each use, or every two
    cuttings at the most. On US made single cylinder simple air cooled
    engines the oil is the lifeblood and dirty oil will greatly shorten
    engine life.
    However on a Honda you can get much longer use on an oil change,
    they're built that much better.( Honda/Toyo machine and polish the
    internal facings to a much higher degree and use a more porous steel,
    which holds oil on the cylinder walls to a greater degree than their
    American counterparts.)
    I've had several SX series Honda mower and find them to be far
    superior to domestic offerings. That's why they genrally cost much
    more than the run of the mill, they'll give you a lifetime of
    dependable use with the proper care.(I've always let my neighbors talk
    me out of them. They know of my rep as a honest repairman and come to
    me for good lawn equipment at a fair price.)
    I've always been a big fan of Honda, Virtually all my higway bikes in
    the past 40 some-odd years have been Honda with a couple of BMWs for
    good measure.(I had one Goldwing that I put nearly 300 thousand miles
    on before retiring it.)
  19. James Sweet

    James Sweet Guest

    Now that's a little ridiculous, change the oil after every use? That's like
    those people who change the oil in their car every 1000 miles. I've dealt
    with enough 25-30 year old air cooled engines that were still in good
    mechanical condition after obviously many hundreds of hours of use,
    generally they had the oil changed occasionally but certainly not after
    every use. Once a season is perfectly adaquate unless you're running 8 hours
    a day, I change mine every year when I put it away for the winter.

    I just checked in an old (1970's I guess) B&S service manual I have and they
    specify oil changes ever 25 hours of operation so I probably end up changing
    mine a little more often than that, but as you say oil does get combustion
    byproducts in it, same reason a car driven all the time on the highway can
    go a lot more miles between changes than one driven around town.

    As for the lifetime ratings, the number of hours the warranty guarantees an
    engine will last, and the number of hours it's expected to or actually will
    last are two drastically different things, I would be absolutely shocked if
    even the cheapest most shoddy lawnmower engine out there wore out sooner
    than a couple hundred hours even if the oil was never changed (as is often
    the case).
  20. none

    none Guest

    Yeah, Tecumseh did turn out some pretty lousy stuff as late as the
    70's. They started turning that around in the early 80's.
    But, if you look at a Briggs parts manual you'll see they have dozens
    of coils whereas Techumseh has just 2-3. Virtually ALL the single
    cylinder Techumseh's under 8hp use the same coil.
    Briggs plays around with the armature gap width as well as the timing
    and coil output so that it's very difficult to get a good cross on
    used parts.(Makes it impossible for small independent shop owners to
    be able to afford stocking all the myriad number of parts for Briggs.
    something that both Briggs and their larger authorized service shops
    exploit to no end.)
    Just depends on what you're used to working on. Honda's do take a bit
    of care when servicing, such as getting the carb of easily, that's
    where most American mechs have issues. Just takes a bit of training on
    them, then they're easy as pie.(Honda's for instance have a MUCH
    superior top end on their OHV vs. Briggs. Briggs must use some really
    cheap steel in the rocker arms and adjuster nuts as they either shake
    out of adjustment or wear out after just a years use. I have to use
    super strength locktite on the adjusters of Briggs just to get them to
    stay put. I won't even elaborate on the nightmare of their aluminum
    Well... high altitude can require a bit or retuning but both engines
    are so simple in design that altitude seldom makes that big a
    Actually both Briggs and Tecumseh use primer bulb carbs.
    What model Briggs engine are you using that doesn't have a Walbro carb
    and primer bulb?
    Yes sad but true. I have an older Fluke and wouldn't part with it for
    anything.( 8060A made in the USA.)
    Heck I still have a small fleet of Simpsons from my day's working in
    my father's electronics shop and they're still going strong.(Not to
    mention all the early B&K test jiggs and generators sitting in the
    corner of my shop that're still doing a bang up job.)
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