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2 3.5 Hp Briggs won't keep running

14 years ago

I have fixed tons of techumseh and briggs vertical shaft engines but I have two edgers, one a 'pro' and another a very nice McClane and both have 3.5 hp Briggs IC engines on them. The use the standard square paper air filter on down draft carbs. The carbs have a diaphram on the muffler side with a spring plunger and the tank suspended under each. Hopefully that tells you what you need to know to visualize the things.

Neither has run in a couple of years so I dumped out the foul old fuel (added it to my truck to recycle) and then proceeded to clean the carb diaphrams. After making sure the surfaces that the flap hits are clean (one was clean, other was foul) neither will run except by having starting goo sprayed in them. Run for a bit, die. Thing is when I removed the diaphram the 2nd time, there seems to be fuel in there. I even counted turns - removed the needle screws, sprayed cleaner in, and put them back as is. Both are at 1 turn as how I got them. I did clean the fuel pickups and when tank was removed, that 2ndary small tank has fuel in it, so I'd think fuel was circulating.

So whaddyer think? Is there some jet hole that is hard to see/get to that I missed? That'd b my guess, but I don't know where to look?

Thank you O River of Knowledge!

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Comments (3)

jgreissi
14 years ago
when they don't run they will get goo. You will need to clean out with carb cleaner, compressed air, and as a last resort a piece of wire. Keep cleaning until they run. That green goop that the fuel turns to is tough stuff. You may even need to go get a carb kit with the welch plugs and really take it apart to get it clean.
milo2000
14 years ago
I have the same issue with a new one that was on a low end mower. Get it started and it dies after a few seconds. Also the recoil starter stripped out as it had plastic internal parts. not very well built engines. Hope you get yours running. Someone else on here told me to get the $4 diaphram kit for the carb. He said ethanol fuels are hard on these rubber parts.
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I recommend using a NGK BKR5EIX pt. # 6341 spark plug . IT will last 8 - 10 years depending on the hours per week it is used, commercially a good 5-6 years . The other problem is the fuel filter. An in line filter like a NAPA 3012 will filter out the the trash that the factory screen filter allows to get to the carburator. The carburator is another problem as water gets is the gas much quicker . Take bowl loose with a long pair of needle nose pliers & clean if bowl leaks gas may need to get the 2 gaskets to bowl. Make sure you have your model # . Fuel is another issue as there is more alcohol in gas these days . Premium gas may help if you don't use daily BUT the product that I have found that works best to disperse water in gas is REDLINE SL-1 fuel additive. 1 ounce per gallon will make the alcohol & water disapear. Exception to this would be when you see water on the bottom of the tank . In this case drain the tank first before cleaning the bowl of Carburator . Just a reminder to never leave the switch on when the motor is not running . Most 14.5 B & S have an electric switch that allows fuel to go through carburator when switch is on. If that does not fix your problems you have a spark issue , a valve clearence adujst hot or cold ? or broken connecting rod . Mechanical issues should be taken to a specialist !
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iarnstein
Original Author
14 years ago
Well, the lawn mower engines - "Q" series, etc, they just need that $4 diaphram and its no big. In this case I have used a lot of carb cleaner and my favorite cleaning wire. I am just wondering where the main jet is on the thing. Remember this is a horizontal shaft edger motor which has a metal carb with the diaphram in the side of it, rather than the diaphram between the carb and the tank. I have done a ton of those things.

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