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help with briggs and stratton mower engine

This is a discussion on help with briggs and stratton mower engine within the Small Engines forums, part of the Tech Support Forum category. i've got a 6.5hp briggs engine on my craftsman mower. mower is probably 5-6 years old. i got this piece


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Old 02-27-2009, 02:24 PM   #1
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Evil

i've got a 6.5hp briggs engine on my craftsman mower. mower is probably 5-6 years old.

i got this piece from a friend, it had been sitting for a couple years bc he couldn't get it to run. when i got it, i cleaned the fuel tank, got fresh fuel in, got a new carb (old one was just too gunked and wanted to start fresh), put a new air filter on. the mower ran fine for an hour or so, but then died (not out of gas).

well now i can't get it to start at all. it feels like there is some sort of air leak, as pushing the primer bulb just sucks in air. i drained the tank again with fresh fuel in case there was still some gunk, and put a new inline filter on the line. i have a new fuel line, new breather tube, new carb (which i also have cleaned out with cleaner), new air filter, new gasket between the carb and air filter back plate, and a new primer bulb. but it still just won't prime. the mower will fire right up when i spray starting fluid in, but then will die after a couple seconds.

at my wits end here!! thanks in advance

edit: it is a 123k02-0183 engine.

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Old 02-27-2009, 02:45 PM   #2
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Hi & welcome to TSF.

What you are describing is almost certainly fuel starvation. Take the fuel bowl off the carb, exercise (gently) the float up and down and see if fuel flows. When the float is down, fuel should flow freely and stop when you push it up.

Let about 1/2 a cup of fuel flow through the float valve as this sometimes dislodges any remaining stubborn gunk. - No Smoking whilst you do this

See if it will run after you have done this - if not, you will likely need to strip the carb and clear all the jets - if you do this - just poke a plastic tooth pick (not steel wire) thru the jet holes to ensure they are all clean.

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Old 02-27-2009, 02:49 PM   #3
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i have a new carburetor though - which i have cleaned already...do you still think it could be clogged?? i should at least be able to get it to prime, but pushing the primer bulb does nothing but suck air. even if the jets were clogged, it should still prime right?
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Old 02-27-2009, 02:55 PM   #4
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Yes it should prime - but only if fuel is passing thru the float valve and properly filling the bowl to the correct level.

My suspicion is some of the remaining gunk has found its way into the float valve (needle and seat) and that is stopping the fuel from getting to the bowl from where the primer is supposed to collect it from - hence you are only sucking air.

You don't need to take the carb off - just undo the bolt at the bottom of the bowl and you should be able to exercise the float and check for fuel flow from there.

If you don't get a proper flow - then you will need to remove the float valve and carefully clear the opening.
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Old 02-27-2009, 03:19 PM   #5
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well, i have proper fuel flow to the bowl. took the bowl off, and let the gas come out...probably a couple cups worth. it was flowing free and clear. the fuel flow stops as it should when the float is up.

any other tips? :(
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Old 02-27-2009, 03:26 PM   #6
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OK - I take it that the "lill devil" still wont start except if you spray easy start into it.

Just one more quick test - with the fuel bowl full, does the engine start and run at all?? If it just starts and runs for a few seconds - then almost certainly there is some muck in the main jet and you will need to pull it out and clear all the holes.

If it starts and runs for a little while (like several minutes) but then dies - try starting and running with the fuel cap loose - if that fixes it - then it will be a blocked breather hole in the fuel cap which you will need to clear.
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Old 02-27-2009, 03:32 PM   #7
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nope, it won't start at all unless i spray fluid into it. it will only run for a few seconds when i do that, then die. if i don't spray, no starting! (grr)

so, sounds like i should clear the main jet then huh. and i'll go ahead and check the breather hole in the cap too while i'm at it.

thanks for the tips! i'll report back. :)
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Old 02-27-2009, 03:42 PM   #8
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Happy to help and yes - pls report back as your results will help others at TSF.

The main jet is likely to be the "bolt" that holds the bowl on - so give that a thorough clear out 1st.

Make sure the little hole about 3/4 the way up the side is clear also. That is fairly easy to do - so how you go then.

If that doesn't get it going, then the other jet/s are a little more problematic but often a good squirt of compressed air can clear these rouge bits of muck without having to strip the carb
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Old 02-27-2009, 04:21 PM   #9
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Cool

IT RUNS!!!


so, i sprayed down the bolt real good, buttoned it back up, sprayed some fluid it, and lo and behold it ran! even though i cleaned the crap out of the carp, i guess i (embarrasingly) didn't clean the main jet well enough and it was still plugged. lesson learned, for sure.

it did run a tad rough the first time (i still had the air filter off) so i threw that on, and it started, then stumbled and died...



this time, it was just out of gas all the gas tinkering and flowing had emptied out the tank

so, filled er back up, and she started right up. i did notice though, that the primer bulb still doesn't seem to "suck fuel", only air. but i'm wondering now that it's running if that's just normal. either way, i started it several times and it fired on the first pull every time.

thanks again for the help!
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Old 02-27-2009, 04:58 PM   #10
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No problems and congratulations on a job well done
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Old 08-09-2009, 03:06 PM   #11
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I just registered so that I could say, "Thank You" for this thread. I had the same problem today with a Troy Bilt 020316 3000 psi Pressure Washer with a Briggs & Stratton 875 series OHV engine. I decided this AM to pressure wash the gunk of my gutters on the front of the house but I could not get the dang thing started. I just used it less than two months ago on the driveway without issue. This leads me to beleive that it shouldn't have been varnished-gas stains or bad gas (works in lawnmower). I could push the primer bulb (red) several times and it would act like it wanted to start. But if I didn't use the primer bulb; nothing; wouldn't even think about it. I replaced the spark plug and verified the gap and confirmed that I had spark while holding against the engine block. I had the carb apart already once today but didn't notice anything unusual; still the same symptoms. I knew it was getting fuel becuase of the primer-bulb and the float bowl was full everytime I took it apart (fuel was 'almost' there). Oh, and of course the dang thing is only out of warrently by less than six months. Then after giving up, on my way to the shower, I came across this thread which convinced me to try again.

I took the carb apart (again) and used a long bobby-pin to clean the gunk out of the float bowl bolt (bottom) and also cleaned out the gas-cap vent hole (tiny).

After seven hours of screwin' around with this thing today, it finally started on the second-pull. THANK YOU!!!!!!!

Now I can have a beer and sleep well tonight without wondering why my dang $400 pressure won't start. Things like that will just bug a guy don't you know, LOL...

Thanks again and regards,
Al
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Old 12-04-2009, 03:00 AM   #12
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Had the exact same issue as all of you and cleaning the carb and main jet again worked. Thank you so much. The issue was driving me nuts...I'm very glad this thread was still up. I had replaced the spark plug, filter, new gas, new oil. Cleaned the carb/main jet but must have had more gunk in one of the holes. I used a wire with bristols that is used to clean teeth with plus carb cleaner and a can on compressed air. The tiny wire brush worked well getting into the carb and the main jets tiny holes.

Thanks again!
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Old 01-01-2010, 09:06 PM   #13
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yes cleaning main jet helps sometimes it looks clear but untill you actually look close or poke a small plastic rod at it you realize its restrictted or blocked

the other condition for this symptom is a warped backing plate - sometimes fitting 2 x primer gaskets to the backing plate will fix or simply removing the primer bulb and cleaning the screen behind the bulb if it has one and making sure this passage is clear to the carb flange the passage to float bowl is clear as well- also check float bowl o ring is sealing / fitted correctly ( loss of pressure in bowl )

pressure pulse from bulb is tranfered to fuel / float bowl and forces fuel up to emulsion tube into the venturi raw fuel for start

cheers mstpops
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Old 01-01-2010, 09:17 PM   #14
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Sounds like classic carb blockage / fuel jet blockage symptoms.

Sorry - but you need to strip the carb and clear EVERY little port / hole in all the jets. Start with the main jet 1st. as that is usually the culprit.

Take the main jet out and poke a thin wooden or plastic (NOT STEEL WIRE ) tooth pick or small / thin piece of copper wire thru all the holes and ensure they are all clear.

Also look to replace the fuel line if it looks dodgey - else give that a really good clean out - just as you did with the fuel tank.

Once the fuel delivery system is cleaned propely - the damned this just has to start and run - good luck with it all

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