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J.R., Small Engine Technician
Category: Small Engine
Satisfied Customers: 7445
Experience:  Owner of outdoor power equipment business, repairing all makes and models.
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briggs small engine model 31C707-0230-E1 problem excessive

Resolved Question:

briggs small engine model 31C707-0230-E1
problem: excessive smoke after 10-15 minutes working, after it decreases power and after 1 hour working shuts it off itself and only after cooling will start work again.
when cool it starts well without any smoke.
new air filter and new engine oil 10W-30.
Please, give advise regarding possible cause of problem above.
Thank you in advance.
Submitted: 7 years ago.
Category: Small Engine
Expert:  J.R. replied 7 years ago.
The first thing you need to do is check the compression on the engine. If the engine has a lot of hours on it then the cylinder rings may be worn.
Customer: replied 7 years ago.

I agree, that it would be the one of the reason - cilynder or piston rings. But

connecting rod was broken and replaced 1 year ago. After it everything was OK (50-80 working hours)!

This problem happened suddenly. What about carburator adjustment or exhaust system problems?


Expert:  J.R. replied 7 years ago.
You may want to check the valve clearances. They are suppose to be adjusted every 50 hours. The spec is .003" on the intake and .005" on the exhaust.

To adjust the valves perform the following. Remove the valve cover. Rotate the engine CLOCKWISE until the piston is at top dead center on the compression stroke (both rocker arms will be loose). You will then need to use something to measure with and then turn the engine until the the piston travels down 1/4" in the cylinder bore. Use a pencil and stick in the plug hole and find a reference point and put a mark on the pencil. Pull the pencil out and then put another mark on it 1/4" higher. Put the pencil back in the plug hole until it touches the piston and then turn the engine CLOCKWISE until the top XXXXX XXXXXnes up with your reference point. Once you have the piston set at this position you will need to check your clearances. You will then want to adjust the clearance accordingly with the adjustment screw.
Customer: replied 7 years ago.

Of course, there are a lot of reasons for excessive smoke. But

I asked about possible problems with carburator (not proper mixture) or exhaust system which can be involved in this problem.




Expert:  J.R. replied 7 years ago.
A carb problem will not occur after 10-15 minutes. The exhaust could be plugged up but I doubt it. Have you checked the breather valve on the engine? Whay are you using 10w30 oil?
Customer: replied 7 years ago.

1. With carburator - thank you. I believe your experience.

2. How to check breather valve?

3. They recommend oil 5W-30 (below 32F) and 10W-30 (above 32F). May be I am wrong? What type of oil do you recommend?.


Expert:  J.R. replied 7 years ago.
SAE 30. See attached link from the Briggs website. Take a look at the 10w30 and what they say it can do.
Customer: replied 7 years ago.

1. Re oil - thank you. This is understandable. I will try, but I was using before during 5 years the oil 10W-30 and had no problems with smoke.

2. What about the engine breather valve - how to check it?



Expert:  J.R. replied 7 years ago.
There is really no way to check it. The best thing to do is take it off and spray it out real good with some carb cleaner. The brather valve hose will lead to the air cleaner.
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