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16 hp briggs 28u707 blown?

Discussion in 'Mechanic and Repair' started by milkman2, Mar 17, 2007.

  1. milkman2

    milkman2 LawnSite Member
    Messages: 4

    I have a 16 hp briggs that is blowing oil from the carb.The engine runs but the the exhaust glows cherry red and the float in the carb sticks.any suggestions would be greatly apprerciated.http://www.lawnsite.com/images/smilies/smile.gif

    DOLMARatOS LawnSite Member
    Messages: 173

    Freindly advice would say....Pull the cylinder head. Better than 75% chance that you have a blown head gasket between the cylinder and the push-rod valley.

    Simple to fix. Would cost you 1.5 hours labor at most shops or you can do it yourself and rebuild the carburetor for less than 50 bux in parts, etc.

    make sure you change the oil after the head gasket.

    We see a ton of these. They make the oil blow out the breather in the carburetor, then they make a knocking noise and when they get real bad they smoke like a bad set of rings under load. Pretty much a 90% failure rate on heavy use equipment.
  3. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 963

    Float sticking would be totally unrelated to a blown head gasket.
    How do you know the float is sticking? Severe flooding or???
    Exhaust glowing red could be a symptom of a couple different (and possibly related) things.
    Is this happening during daylight? At night, some mufflers can have a red glow, especially under load.
    It could be unburned fuel accumulating and then burning in the muffler (maybe a sick/dead cylinder from a blown head gasket?).
    It can also be a symptom of an excessively lean condition.
  4. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    If the float is sticking (float needle valve not seating) it could have filled the crankcase with fuel. This would cause a high and thin oil level and cause oil to be pumped up into the carb. through the breather system.
    Check oil for fuel contamination and change, Rebuild the carb. (New float needle) check fuel tank for trash, flush fuel lines and replace fuel filter.

    A blown head gasket can be found with a leak-down test or compression test in this case by comparing readings between the two cylinders.

    Most small engine mufflers will glow in the dark but most are not ran at that time to be seen.

    DOLMARatOS LawnSite Member
    Messages: 173

    If the carburetor float is sticking or the needle valve is leaking due to debris with an overfilled crankcase then a head-gasket may not be the problem. But, if the crankcase is not overfilled then proceed to other problem areas.

    It would be nearly impossible to compare "the two cylinders" on this 16 HP engine as a 28U707 B & S is a single cylinder motor. 15 years as an MST?

    If this unit rolled into my shop I'd first check the oil level and see if fuel is present in the crankcase. If no fuel present, pop the valve-cover and check the valve-lash, thenpull the head. Simple process of elimination to the smoking problem. No sense in a leak-down test because these head gaskets being blwon will point towards a bad cylinder. If it's smoking and blowing oil out the breather then it's either a carburetor causing fuel in the crankcase, a blown head-gasket, or a worn-out / blown engine. I'm sure I could get flamed on this one with all sorts of other tests to perform before "wasting time" and the customer's money on pulling the head. But it's faster than half the tests.
  6. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    As you see what time I made my post !!! I WILL have my coffee and WAKE up before posting in the future. :hammerhead:

    DOLMARatOS LawnSite Member
    Messages: 173

    I agree rob. 0530 is a dark hour. Coffee, maybe a little eggs and toast. Possibly a smoke or a chew. Then sit down to read lawnsite before heading off to kill a sunday.

    It's insane how many failed head gaskets we see on 28 and 31 cubic inch briggs singles. When they first started happening years ago we mis-diagnosed a few as worn out or bad engines. Now, if a motor smokes, uses oil and doesn't have a crankcase full of fuel.....it's straight to the head gasket. We're also seeing a lot of burned up starters on the 28 and 31 due to the mechanical compression release spring crapping out on the camshaft. Every head gasket and camshaft is accompanied by an overheated motor.
  8. milkman2

    milkman2 LawnSite Member
    Messages: 4

    Thanks for the responses. The engine stalled and seemed to fill the cylinder with gas since the starter would'nt turn past compression.I forced it past and got it started.When it cranked, it would spit oil from the carb occasionally.(every 20-30 seconds) The carb was filling with gas that was visible in the intake. The crankcase was dilluted with gas also. I tapped on the float bowl to stop flooding and changed the oil.When I finally got it to run I noticed the muffler glowing cherry red in daylight and oil still spewing.
  9. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    It will do that until all the fuel/oil burns out of the muffler, But something should be done with the carb. to prevent it from happening again.

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