Briggs & Stratton 24HP

Discussion in 'Mechanic and Repair' started by thom, Oct 11, 2013.

  1. thom

    thom LawnSite Member
    Posts: 146

    What causes the valves to stick?,'
    and how to prevent sticking again.
    My mower wouldn't start, I removed
    the valve covers.On one head, both
    push rods were bent.
    both valves were lightly stuck.
    A tap with a dead blow hammer, and
    all is well.
     
  2. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Posts: 728

    9 out of 10 times it is due to old, stale fuel... Especially if ethanol is now used. The ethanol acts like a solvent that breaks up varnish from old and stale fuel then tends to become sticky or tacky and will cause valve/valve guide issues!
     
  3. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Posts: 2,231

    Jeff, I can't say that I could agree with your statement that 90% of stuck valves is a result of old/stale fuel. The largest portion of stuck valves problems, in my experience, is from over heating, either as a result of obstructed cooling fins or low oil condition.

    I won't deny that ethanol laced/old/stale fuel isn't a problem but I haven't had an indication that it is the cause of any stuck valves problems I've encountered.

    Just my two cents.
     
  4. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,024

    OK Guy's...... Here's my take,


    I've seen this more than a few times on equipment that had been left sitting up for a period of time, Either after the first cranking revolution or seconds after start-up the valves stick open..... Most commonly the intake.....



    This I've seen as well a few times but will add to low oil conditions with, Fuel contaminated oil or just flat out thin nasty oil from lack of proper oil changes.....


    The fact that Thom was able to "tap with a dead blow hammer, and
    all is well" leads me to believe his issue was/is a result of Dutch's assessment (over heated/lack of proper lubrication)......

    My theory is based on...... Every single valve I've found gummed up from fuel residue, They have required the valve stem be sprayed with carb & choke cleaner and tapped in and out many times to work the gum out of the guide. Then they can be removed checked then oiled and reassembled........
     
  5. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Posts: 2,231

    Well, Rob, I would acknowledge that your experience is broader based than mine--I've just not seen many engines that have sat much longer than over the winter months. Maybe old age really is kicking in:confused: but I just can't recall stuck valves that were sticky/gummy--they were carbon loaded.

    Is it possible that the "hotter than hades" temps you get in the southlands may contribute to the problem? I can see that long term storage in those temps may be a factor.

    My classic stuck valve story-------a lawn care company, at leaf cleanup time, sent their two crews out with only 2 stroke fuel(I'll let you interpret the reason on your own). By 11:00, their first day out we had two BG wheel blowers(Briggs L heads) and a BG leaf loader(Briggs 18vanguard) in the shop with stuck valves.
     
  6. Sharpcut 1

    Sharpcut 1 LawnSite Senior Member
    Posts: 450

    Your valve guides may have also moved from overheating. Smack from a dead blow will temporarily stick them back into place, but when heated up again may cause to move. Don't usually see both valves stuck, unless severly overheated. Have had a lot of Briggs OHV engines where the guides slid, holding open the valve.
     
  7. herler

    herler LawnSite Fanatic
    Posts: 5,144

    I usually think someone didn't change the oil.
     
  8. thom

    thom LawnSite Member
    Posts: 146

    This mower is a recent acquisition.
    I don't have any service records for it,
    and was told it runs rough.
    The engine oil didn't even look like oil.
    I changed the oil, I ran the engine for about
    15 minutes then parked it for the night.
    The next morning, it would not start.
     

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