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Ranwell1
Ranwell1, Small Engine Technician
Category: Small Engine
Satisfied Customers: 10085
Experience:  I Own a Lawn Mower Sales and service business (37years). Have 2-cycle and 4-cycle certification.
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Spark plug keeps oiling up with thick black oil and then lawnmower

Customer Question

Spark plug keeps oiling up with thick black oil and then lawnmower doesn't work but if spark plug renewed it is ok but only until next time it is used. Have tried changing oil but problem persists.

Would it help if system is flushed before further oil change and if so what is recommended for that?

If not, what else do you advise?
Submitted: 5 years ago.
Category: Small Engine
Expert:  Rick replied 5 years ago.

Is the mower being tipped or is it remaining level?

 

Does the oil in the crankcase smell like gas if you sniff it?

 

What level is the oil at on the dipstick?

 

How old is the engine?

Customer: replied 5 years ago.

 

Remaining level

 

No smell fromoil

 

Oil level normal

 

3 years old

Expert:  Rick replied 5 years ago.

What weight oil are you using? And what horsepower engine are we talking about? Is it overhead valve?

Customer: replied 5 years ago.

 

Oil is same as always used. Don't know horsepower. Its a lawmower for goodness sake. If that's the best you can do just forget it.

Expert:  Ranwell1 replied 5 years ago.

Just to put my two cents worth in here. The other expert is definately on the right track. Asking all these questions and getting the correct answers is the only way we are going to narrow down the possible causes of your problem.

 

Why did he ask these questions?

 

Is the mower being tipped or is it remaining level?

If a mower has been tipped, the air filter will fill up with oil and cause the engine to burn rich...causing the spark plug to carbon up like what you are talking about.

 

Does the oil in the crankcase smell like gas if you sniff it?

If the carburetor is overflowing because of dirt, gum, or varnish, it can fill the crankcase full of gas...thinning out the oil and causing the engine to burn oil very quickly and carbon up the plug. Also he asked this because if the crankcase is full of gas, that tells him that the carb must be rebuilt and it is giving too much gas to the engine also carboning up the plug.

 

What level is the oil at on the dipstick?

He wanted you to tell him this because this is a tel-tale sign that the crankcase is full of gas if the oil level is too full. If the oil level is low, then that tells him that the engine may be ruined because of lack of oil. The cylinder and piston may be scored and this would cause the engine to burn oil and to carbon up the plug.

 

 

How old is the engine?

This lets him know if the engine is old enough to be worn out. A worn engine will start to burn oil and carbon the plug.

 

 

What weight oil are you using?

Too many people don't know that if you use multi-grade oil (10W30 or 10W-40) Engines start burning oil very rapidly. You should always use a straight weight 30W oil in small engine like your's.

 

And what horsepower engine are we talking about?

This gives him the size of the engine so that he can picture other possible problems that may be unique to larger or smaller engines.

 

Is it overhead valve?

This lets him know if he should start giving you information about overhead valves. They tend to get out of adjustment much more than L-Head valve engines and also oil is more likely to find its way through the valve train into the combustion chamber. Causing your problem.

 

It is NOT...JUST A LAWN MOWER as you stated. It is a very finely tuned piece of machinery that can have many different causes of your problem.

 

Give this expert a chance to help you.

 

 

Please click "ACCEPT" or I won't get paid.

You may also consider sending a bonus if I have been helpful,Please leave positive feedback this is how I'm rated. Thanks

Customer: replied 5 years ago.

 

Sorry. Forget it. Most disappointed. I'll get someone locally to look at it.

Expert:  Ranwell1 replied 5 years ago.
Good luck. But I bet one of these answers I gave you is what the problem is.
Customer: replied 4 years ago.

 

I found your web-site when browsing for details of local Briggs & Stratton agents. I thought that a simple question could have brought a simple answer but instead of getting an answer I just get asked questions.

 

I have always used the recommended oil. I have always measured the correct quantity of oil. I have always changed the oil and the sparkplug at the start of each summer.

 

I use the lawnmower on a level surface and the lawnmower worked fine until two months ago since when I have had to change the oil and sparkplug about three times as the plug keeps oiling up and the oil keeps going black.

 

My original question described the problem well and all I wanted was a straight answer. As I've said, however, I'll now just get someone locally to deal with it.

Expert:  Ranwell1 replied 4 years ago.

Sorry that you feel that way. In many cases there is NOT simple answer.

 

I would be interested to find out what the Mechanic finds when you get it back from the shop. Most likely he will find that the problem is one that we have discussed, but if noy, I sure would be interested to find out what it is.

 

Good luck.

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