Briggs L-head; what an engine!

[JBtoro]

Family member brought me his Briggs 7.25 on a 5 year old Troybilt walk behind. I hadn't seen it nor serviced in a year. Turned it on it's side to drain the old oil; nothing came out. Dipstick showed nothing either. He had somehow failed to check the oil during the last year and also let the air filter get completely clogged. I feel certain that he mowed with it many times in this condition or when the level was quite low. So I put oil in it & it started right up. I ran it for at least 30-40 minutes & it ran & sounded great with no smoking whatsoever.

 

[JBtoro]

Follow up on my original post. What specifically would cause an engine with a clogged air filter to go from full oil in the sump to no oil? The owner told me that the engine was not smoking. It surely didn't evaporate. I mean I can see where a clogged filter would cause overheating and eventual ring problems thus causing the oil to dissipate from burning. However, to not smoke but otherwise go from full sump to no (or minuscule) oil in the sump?? That's what I'm trying to understand.

 

[StarTech]

Not all oil problems will cause an engine to smoke; just how it is. I have Briggs OHV engines with a blown gasket to consumer lots of oil and not even smoke as most modern oil are now semi smokeless. Also the oil used matters. A year or two ago heard about the poor quality oil the Dollar General Stores was selling that getting consumed by engines at a high rate.

You mention a clogged air filter. The engine was problem darwing extra in through the crankcase vent valve assembly which would draw in some oil.

You also mention been about a year since you have seen the mower. I have a similar thing last fall with a Swisher walk behind trimmer where the operator never bother to check the oil. What was left in the engine was like molasses especially during the 40F temps that I was working on it in.

 

[cpurvis]

Follow up on my original post. What specifically would cause an engine with a clogged air filter to go from full oil in the sump to no oil? The owner told me that the engine was not smoking. It surely didn't evaporate. I mean I can see where a clogged filter would cause overheating and eventual ring problems thus causing the oil to dissipate from burning. However, to not smoke but otherwise go from full sump to no (or minuscule) oil in the sump?? That's what I'm trying to understand.

A clogged air filter causes a rich mixture. Rich mixtures run cooler than a normal or lean mixture and will blacken spark plug electrodes. Oil consumption will also leave black residue on spark plugs but it will have a wetter appearance than the carbon deposits left by a rich mixture.

Only three ways for oil to disappear from an engine. 1. It gets drained or suctioned out; 2. It gets burned and goes out the exhaust; and 3. It leaks out, leaving a trail.

 

[tom3]

Oil smoke is basically unburned oil. If the motor is actually burning the oil it might not be visible, might smell a bit though. A whole season around here would sure make it possible to burn most of 18 or 20oz of modern oil, especially this year.

 

[seattlepioneer]

I used to work in the slide rule days. And logarithms.

I remember learning to interpolate tables of mathematical functions using a slide rule to do the calculations. That was circa 1965 or so.

In 1990 I went back to learn the math I'd never learned very well, and completed two quarters of regular college calculus before bailing out of the third quarter of calculus ----twice.

Computers and calculators were readily available at that time, and I remember how much easier things were when you could easily graph equations to better understand what was going on. And of course it was far easier to get much more accurate functions than with a table of values and interpolation.

So my experience was that computers made it much easier for marginal math students like myself to learn a lot more math. I wouldn't be surprised if that was true for talented math students as well, or most of 'em.

I had a friend born about 1937 in Germany to a highly talented mathematician. He was able to visualize the graphs of complicated functions without doing the math to calculate them. He wound up working at Penemunda on the V2 rocket with Werner Von Brown, and he and his family, including my friend, entered the United States through the Mexican border with "Operation Paperclip" after end end of the war.

He closed out his career as a Professor of Physics at the University of Washington.