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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 28894
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a briggs and Stratton model #128m02-0926-b1 and I

Customer Question

I have a briggs and Stratton model #128m02-0926-b1 and I cant get it to start. I have replaced the spark plug, magneto, checked to make sure the carburetor is not clogged and still no luck. its a 725ex series. It ran fine and then I pulled it out to mow the lawn and it started backfiring then it just wouldn't do anything.
Submitted: 1 year ago.
Category: Small Engine
Expert:  Curtis B. replied 1 year ago.

If you remove the spark plug and ground it , do you have spark? If it has spark, put a teaspoon of fuel into the spark plug hole, re-install the spark plug and see if it will start for a few seconds. If you get no start, the flywheel key needs to be checked, as engine may be out of time from a sheared flywheel key!

Customer: replied 1 year ago.
Getting spark but still won't start. Will check flywheel key tomorrow.
Expert:  Curtis B. replied 1 year ago.

OK>

Customer: replied 1 year ago.
Sorry for the long delay in getting back to you but I haven't had the chance until today to check flywheel key. so I checked the key and it's still in good shape and I rechecked the spark from the plug and it's still getting fire so I'm lost at this point.
Expert:  Curtis B. replied 1 year ago.

Have you removed the spark plug and held your finger over the spark plug hole while you crank it, to see if it has enough compression to move your finger. If not, you may have a stuck valve!

Customer: replied 1 year ago.
I removed the cover to check the piston and valves and the are all moving freely.
Expert:  Curtis B. replied 1 year ago.

But does it have compression? Spark, fuel , compression, and timing , and it should run, if the fuel s good.

Customer: replied 1 year ago.
Just tested it for compression and it has enough compression to blow out a piece of tissue but not enough for me to feel it on my finger.
Expert:  Curtis B. replied 1 year ago.

You say the piston is moving? Then you have a stuck valve, that is not seating.

Customer: replied 1 year ago.
that means I need to remove the valve an clean it out or do I need to replace it.
Expert:  Curtis B. replied 1 year ago.

Valves are in the cylinder head, Head has to be removed to free up the valve or replace it!

Customer: replied 1 year ago.
On this particular lawn mower there is an opening for you to be able to remove the valve spring and remove the valve. I just need to get the valve spring tool.
Expert:  Curtis B. replied 1 year ago.

Flat head design, head has to come off, then valves can be removed with valve spring tool. You may be able to reach in the valve spring hole and flip the valves, may free it up!

Customer: replied 1 year ago.
Ok. Will try that out. Thanks for your help.
Expert:  Curtis B. replied 1 year ago.

Thank you! Please rate to close.