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B&S 18HP will not start

The mower is a husqvarna with a B&S model 31Q777. The engine will turn over but will not start. I've put in fresh fuel, checked the fuel system, cleaned the carb, checked valve clearance, checked push rods, checked woodruff key on flywheel, checked spark at plug, and checked timing events. I know i'm looking over somthing simple but i just cant put my finger on it.

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  • Briggs & Str... Master
  • 1,917 Answers

Check compression squirt a shot of starting fluid in the carb see if it wont start check all your safty switchs

Posted on Jun 07, 2014


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Posted on Jan 02, 2017

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SOURCE: MTD Yard Machine 22'', 4.5HP, 190cc push lawn mower won't start

The primer bulb might be damaged, or the carburator diaphram could have been damaged if carburater cleaner was used.

Posted on Jun 19, 2009

  • 11 Answers

SOURCE: 4.5hp Brigss & Stratton engine.Engine runs rough.

Ok, check the air filter, it could be clogged. A clogged air filter won't allow a proper air-gas mixture. Then check the carb. make sure that it is clean, or if anything doesn't look right. You might have to get another carb. After that check the intake it could be clogged but this time a clogged intake means that there isn't enough fuel getting to the combustion chamer.

Posted on Aug 12, 2009

  • 496 Answers

SOURCE: Yard-man model 12a-979L401 won't start (9 years old)

My dad always taught me, rest his soul, that basic 101, if you have gas getting to spark, SOMETHING out to happen.
I'll ask a series of questions and propose some possible solutions. Hopefully we'll crack this mystery. Warning, this might be a tad lengthy... ha
1. Is the spark plug firing?
To check the coil that sends spark to your spark plug and the plug itself:
You can remove the spark plug from your engine and reconnect it to the spark plug wire while it just lays on your mower. pull the starter rope (make sure you're holding down the kill lever on the handle). Look at your plug end as you pull the rope.
Got spark? If yes, go to the next step, flagged ***. If no, look at the end of your spark plug that would go into the engine. The "L" shaped finger should be gapped from the small circular shape on the plug... this is the "gap". Your manual may provide specs on how wide this gap should be. If there is no gap, your plug won't work properly. The "L" shape is a soft metal and can be bent... create the proper gap. Try the test again to see if the plug is sparking. If not, you may have an issue with your coil.
***Yes to spark. Let's look at the gas issue now. OPTION 1. I will tell you that in my experience, water in gas is a major culprit for a mower not running. You've replaced all the filters... good.
I'm not sure of your mower, but most models have a "bowl" bolted to the bottom of the carburator. Sometimes moisture can get in the gas, get trapped in the bowl and won't go away or won't allow gas to get to the spark. Loosen the bolt... it's ok if gas from the bowl spills from this, the bowl doesn't hold much gas and it won't drain your tank. Plus, this means your carbuator is allowing the gas from the tank to the bowl. As you are looking at the gas spilled on the mower deck, see if there are beads of water in it. As you know, water and gas doesn't mix. This would be a tell tale of the problem. I would carefully remove the bowl from the carb and wipe it dry, then reassemble the bowl.
To be on the for sure side that you have no more water in your system, you could disconnect your fuel line from the gas tank and drain it out. Use a jar or container... you can see water in the bottom of it. You can reuse the gas too... just don't include the water!
OPTION 2. If your carb and tank are now H2O free and you're still getting to results, you may have a clogged jet on your carburator. This little pin-hole passage allows gas to pass through to the spark. Sometimes a mower sitting up a while, can cause a laquer effect to gas and it can block this passage. Removal of the carburator from the engine is required and a simple pin can be pushed through this passage to knock a "plug" out.
Geez I hope I didn't miss anything! ha
Good luck to you... I hope it's a quick and easy fix.

Posted on Aug 26, 2009

  • 1 Answer

SOURCE: Troy Bilt model 542(11a-542-q711)has Honda 160cc

I need Gaskets for caboretor

Posted on Sep 08, 2009

  • 10865 Answers

SOURCE: Honda 160cc mower engine starts and dies.

Your carbeurator is crudded up. Get a can of aerosol carbeurator cleaner at any auto parts store. Remove the air filter and spray two squirts of cleaner into the air intake. Start the engine and keep it running by squirting more carb. cleaner into the air intake. WIth a little patience you will clean your carb. and solve your problem.

Posted on Sep 14, 2009

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