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I have a 21 hp Briggs engine on a husqvarna mower. It has…

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Hi, my name is...

Hi, my name is James I have a 21 hp Briggs engine on a husqvarna mower. It has started spitting back through the carb. It will run good for about 30seconds then start spitting or backfiring through the carb. I replaced both head gaskets. have adjusted valve clearance half dozen times. Nothing helps Put new kit in carb no help seems worse if anything Now when the blade solenoid is engaged engine dies instantly

Mechanic's Assistant: Do you have fuel in the tank? If so, is the shut-off valve open and the fuel clean?

Yes about a half tank fuel is clean it seems to be getting plenty of fuel to carb

Mechanic's Assistant: Do you plan on doing the work yourself?

Yes

Mechanic's Assistant: Anything else we should know to help you best?

Not that i can think of i have worked on several mowers but this one has me baffled compression on both cylinders is over 100

Submitted: 1 month ago.Category: Small Engine
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Answered in 8 minutes by:
3/13/2018
Technician: Donald, Small Engine Technician replied 1 month ago
Donald
Donald, Small Engine Technician
Category: Small Engine
Satisfied Customers: 2,319
Experience: I have 25+ years of experience repairing 2 & 4 cycle engines
Verified

Hello. Thank you for choosing Just Answer. My name is***** will be happy to assist you.

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Technician: Donald, Small Engine Technician replied 1 month ago

Do you have the model and type numbers for your engine?

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Customer reply replied 1 month ago
Model 446777 Type 0246E1 Code 040430YG
Technician: Donald, Small Engine Technician replied 1 month ago

Thanks for this information. I will pull up a diagram of your engine.

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Technician: Donald, Small Engine Technician replied 1 month ago

Thank you for waiting. I am back with you.

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Technician: Donald, Small Engine Technician replied 1 month ago

Have you checked to see if your engine is running on both cylinders during the 30 seconds?

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Customer reply replied 1 month ago
it is not a constant backfire it will turn a few rev then spit back if i pull either plug wire off while it is running it stops spitting put it back on and it starts again
Technician: Donald, Small Engine Technician replied 1 month ago

Are you saying that if you remove one of your spark plug wires, your engine will continue to run smooth until you reattach the spark plug wire?

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Customer reply replied 1 month ago
but only on one cyl
Customer reply replied 1 month ago
seems as though i get all the weird problems
Technician: Donald, Small Engine Technician replied 1 month ago

Okay ... Hopefully we will figure out our problem.

I would like to confirm something. Example:

  • If you pull spark plug wire on cylinder #1, does your engine began to run smoother.
  • If you pull spark plug wire on cylinder #2, does your engine began to run smoother.

I am trying to get a clear picture of what is going on.

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Customer reply replied 1 month ago
Correct no spitting back through the carb
Technician: Donald, Small Engine Technician replied 1 month ago

Thanks for clarify. So, the spitting stops regardless of which of your two spark plug wires your remove.

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Technician: Donald, Small Engine Technician replied 1 month ago

Did you set your valve clearances at .005" when your piston was 1/4" past top dead center on your compression stroke?

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Customer reply replied 1 month ago
owners manual recommends twice that
Technician: Donald, Small Engine Technician replied 1 month ago

Did your manual recommend 0.10"?

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Technician: Donald, Small Engine Technician replied 1 month ago

Keep in mind that engine needs three things in order to start up and perform to your satisfaction. It needs Fuel, Spark, and Compression.

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Customer reply replied 1 month ago
correct but i tried them both ways .005 and .010 didnt make any difference
Technician: Donald, Small Engine Technician replied 1 month ago

I do believe that if your compression or spark was at fault, your engine would not run for 30 seconds before the failure began.

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Customer reply replied 1 month ago
both plugs firing and compression is well over 100
Technician: Donald, Small Engine Technician replied 1 month ago

Did you check the condition of the rubber o-rings between cylinder heads and your intake manifold?

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Customer reply replied 1 month ago
replaced both head gaskets and installed new o-rings
Technician: Donald, Small Engine Technician replied 1 month ago

Have you checked the fuel shut off solenoid on your carburetor?

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Customer reply replied 1 month ago
it is working if thats what you mean
Technician: Donald, Small Engine Technician replied 1 month ago

I would like for you to try something when you have an opportunity.

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Customer reply replied 1 month ago
what is that? START LOOKING FOR ANOTHER MOTOR
Technician: Donald, Small Engine Technician replied 1 month ago

Remove the small black kill wires from both of your ignition coils, then start your engine up again, to see if it will run longer than 30 seconds, with both spark plug wires attached.

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Customer reply replied 1 month ago
I had thought of doing that but just hadnt had time This acts just like it was receiving a signal from one of the coils at the wrong time if you know what i mean
Customer reply replied 1 month ago
If that changes the way it runs then what?
Technician: Donald, Small Engine Technician replied 1 month ago

The wiring harness for your ignition coils have a diode inline to prevent one coil from grounding out the other coil. If the diode fails, it can cause ignition problems.

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Technician: Donald, Small Engine Technician replied 1 month ago

If the problem goes away after you disconnect both kill wires, you will need to replace the wiring harness for your ignition coils.

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Customer reply replied 1 month ago
If it doesn't then what?
Technician: Donald, Small Engine Technician replied 1 month ago

When will you have a chance to check this?

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Technician: Donald, Small Engine Technician replied 1 month ago

After I know the results, I will know where to go next, if this is not our problem.

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Customer reply replied 1 month ago
first thing in the morning can we continue this conversation later if needed
Technician: Donald, Small Engine Technician replied 1 month ago

Absolutely. I will be happy to continue working with you until our problem is resolved. There are no additional costs for following up tomorrow.

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Customer reply replied 1 month ago
How will i get back to you?
Technician: Donald, Small Engine Technician replied 1 month ago

This is a link in the email you received from our site. If you click on the link, it will direct you back to this discussion page, and to me.

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Customer reply replied 1 month ago
Ok Thanks a bunch for your help i will try this first thing in the morning good evening or good morning depending where you are, James
Technician: Donald, Small Engine Technician replied 1 month ago

You are very welcome! I am in Texas. Good night.

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Customer reply replied 1 month ago
Hello Donald are you there?
Technician: Donald, Small Engine Technician replied 1 month ago

Yes, I am here.

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Technician: Donald, Small Engine Technician replied 1 month ago

How are you tonight?

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Customer reply replied 1 month ago
I am fine thank, you I hope you are This is James again Itried unpluging the kill wire from both coils. It didnt make any difference in the spitting back I did notice when i tried to kill the engine with the choke pulled all the way out (tried to kill engine that way) it seemed to run better If thats any help
Technician: Donald, Small Engine Technician replied 1 month ago

Thanks for the update, and thanks for checking. If unplugging the kill wires did not make a difference, this lead to possibly a fuel related issue, due to your engine running better with your choke fully closed.

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Customer reply replied 1 month ago
I saw on one of the internet videos that this gas we have now is really messing up the o rings in the carb I ordered a kit to replace these with now with the throttle fully off it runs and slowly starts running faster until it is running wide open and i have to turn the switch off to stop it
Technician: Donald, Small Engine Technician replied 1 month ago

Are you saying that your engine will rev up to fast rpms regardless of your throttle position?

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Technician: Donald, Small Engine Technician replied 1 month ago

If you use your hand to hold your throttle shaft in idle position, will your engine continue to idle and not rev up?

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Customer reply replied 1 month ago
Sounds crazy i know but the throttle shaft does not move.. When it speeds up i can move the throttle from fully off to wide open and it make no difference in engine speed
Technician: Donald, Small Engine Technician replied 1 month ago

When you are move your throttle, are you moving it at your carburetor by hand, or are you using the lever on your mower?

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Customer reply replied 1 month ago
lever on mower
Technician: Donald, Small Engine Technician replied 1 month ago

The reason I asked, is because your throttle cable could be slipping and preventing your throttle shaft from moving as you move your throttle lever. When you have a chance, move your throttle lever as you watch your carburetor. check to see if your throttle shaft is actually moving.

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Customer reply replied 1 month ago
Its not slipping because i had carb off putting o rings in i replaced cable and tightened it securely
Technician: Donald, Small Engine Technician replied 1 month ago

If the butterfly in your carburetor is actually moving as you move your throttle lever up and down, but your engine revs up to high rpms, can indicate a failure in your internal governor.

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Customer reply replied 1 month ago
This reving up only started after i replaced the o rings before it ran normal except for the spitting back only thing it had gotten to the point that it would not idle
Technician: Donald, Small Engine Technician replied 1 month ago

There is something you can try when you have a chance. Remove your governor spring, then start your engine to see if your engine will idle.

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Customer reply replied 1 month ago
Ok i will give it a try tomorrow
Technician: Donald, Small Engine Technician replied 1 month ago

I will be online tomorrow. We can continue from here. While you are at it, double check the movement of the butterfly valve inside your carburetor, just to be sure. Mark the location of your governor spring.

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Customer reply replied 1 month ago
Ok good night i will try to continue tomorrow
Technician: Donald, Small Engine Technician replied 1 month ago

Very good! After we resolve the over revving problem, we can focus on the spitting issue again. Take care and you have a good night as well.

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Customer reply replied 1 month ago
Hello Mr Donald James here are we on again tonight?
Technician: Donald, Small Engine Technician replied 1 month ago

I will be back at my computer at 11:00 pm central time tonight.

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Technician: Donald, Small Engine Technician replied 1 month ago

I am back online. I will be online most of the day on Saturday, beginning in the morning.

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Customer reply replied 1 month ago
Hello I am back, busy last two days are you on line?
Technician: Donald, Small Engine Technician replied 1 month ago

I am online tonight until 11:00 pm central time.

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Customer reply replied 1 month ago
Good evening, I have done as you requested, I hope. I started the engine and it idled pretty much ok. If it slowed down a little bit, then the governor would increase the speed back up as it should. I unhooked the governor from the throttle lever completely. I held the throttle lever against the stop and it idled decent. I worked the throttle lever increasing the speed by hand two or three times. It increased and decreased speed as it should. It idled a short time, then as I was holding the throttle against the stop, it started to increase speed on it's own. I had to shut it down to prevent over reving. Thats where we are now. How much longer time wise do we have to word on these problems. I know to start with, a week time limit was indicated I dont have a lot of free time at this time, so I have a problem connecting with you. Thanks, James
Technician: Donald, Small Engine Technician replied 1 month ago

Hello James. There is not a time limit for us to continue working together on your engine.

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Customer reply replied 30 days ago
Hello Donald. Have you read my response to your last recommendations? I am waiting on you now. Thanks
Technician: Donald, Small Engine Technician replied 30 days ago
Hello James. Are you saying that your engine speed up while you were holding your throttle shaft in the idle position?
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Technician: Donald, Small Engine Technician replied 30 days ago
The next time you start your engine. Spray some carburetor cleaner around the base of your carburetor in the area where your carburetor mounts to your intake manifold.
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Technician: Donald, Small Engine Technician replied 30 days ago
Also, spray some carburetor cleaner in the area whether your intake manifold bolts to your cylinder heads.
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Technician: Donald, Small Engine Technician replied 30 days ago
Let’s see if your engine slows down or if it continues to speed up.
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Customer reply replied 21 days ago
Hello Donald, sorry to take so long in regards ***** ***** last suggestion I started the engine up and sprayed all around both intakes next to the heads and also around the carb. Nothing changed except after running for about a minute with the throttle still fully closed against the screw the engine proceeded to increase speed to almost wide open again. Now what?
Technician: Donald, Small Engine Technician replied 21 days ago

Hello James. Based on what you and I have covered thus far, I feel that your internal governor has failed.

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Satisfied Customers: 2,319
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