Question about Husqvarna 21" Walk Behind Lawn Mower HVL 7021RC

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Butterfly in carb. sticking

After cooling, the butterfly will not close to choke. Have to remove air filter and manually close butterfly

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Posted on Jan 02, 2017

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SOURCE: air leak only idles with choke closed no high speed.

Remove your exhaust manifold. Look into the cylinder with a flash light. You are looking for scratches. Anything larger then a light fingernail is definite proof you need a new cylinder/piston assy.

If it passes that test do the following:

Pour mixed fuel straight into your cylinder until 1/4 full. Slowly pull your saw over while looking into the cylinder. If you see bubbles after the ring/rings go by then you need a new cylinder/piston assy. On rare occasions if no scratches are present on the cylinder wall or piston, you may be able to change just the rings.

Posted on Mar 31, 2009

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Why do i have to run my 96 polaris 400 2x4 atv in half choke when i ride

If you haven't taken that carb apart and cleaned it in awhile - more than likely your jets (what's used to pick the gas up out of the bottom of the carb (the bowl) are clogged up. You can pick up a can of carburetor cleaner with a wire basket inside from any major parts store specifically for carburetors to soak in. The size of a paint can & around $20. Soak the carb in that for awhile after disassembling, make sure none of your ports are clogged - air compressor gun or you can also use keyboard cleaner - air dusters. You want to verify that air can pass through all those ports properly and blowing air through them is how you do it. Carb does need to be completely disassembled to do this. The jets in the carb suck up fuel due to the vacuum the engine creates turning over. Once it starts spinning - it builds up a little suction and everything is fine. When the jets start to clog - one of the ways to force the carb to pull harder is to work the choke. The only thing that choke is doing is operating the butterfly. When the choke is on - the butterfly closes. Making all of that suction stay right there in the carb. Once the bike starts to warm up - you release the choke - and the butterfly will open - allowing more air into the system. You're running at half choke - butterfly half closed - to force those jets to pull harder. If they were clear? No need to run at half choke. Hope that broke it down for you - All The Best, Justin M. 17 South Industries, LLC

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1 Answer

It will idol when choked apon release motor revs big and stalls

So it idles fine when the choke is on but not when its off, am I correct.

When the choke is on, the butterfly on the carb is closed. Meaning that Air is restricted upon entering the carb. This is telling me you still have a fueling issue. As when the butterfly is closed, the engine is getting the optimum amount of fuel and air to burn. However, when you release the choke, you open up the butterfly on the carb mean more air can get into the carb, in turn this draws more fuel through the carb to create that optimum burn.

Yours however isn't getting the fuel it needs when the butterfly is open, meaning its getting too much air and not enough fuel. Check and clean carb, replace any fatigued gaskets and diaphragms.

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1 Answer

Wont,t stay running & gas coming out of exaust

Does it have a manual choke? Have you changed the air filter? Checked the butterfly in the carb? I'd make sure the choke cable is loose and working and make sure butterfly works good. After that, I might check the needle valve which is only for those who are mechanically minded.

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3 Answers

What should happen when you deploy a choke on a lawn mower engine.

Hi Julie:
- When the choke is OFF, the butterfly valve is OPEN. That allows lots of air in (Lean Mixture) and is correct for when the engine is WARM.
- When the choke is ON, the butterfly valve is CLOSED. That makes the engine draw in MORE GAS (Rich mixture) and is used when first starting a COLD engine.
- Fuel in the engine oil is typically a different problem and would be associated with a faulty valve in the float chamber (or other location) in the carb.

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How set up a manual chokein a ford falcon

I put one in a 1970 Chevelle. I bought the hand choke cable with pull lever and under dash mounting bracket. Mounted pull lever under the dash, drilled a hole in the firewall as high as I could, ran the cable out to the engine compartment. Mounted the holding bracket to the motor as close to carb as possible on the intake, then attached to the choke arm that works the butterfly plate in the carb throat. Cut to fit as tight as possible with butterfly plate closed and push lever all the way in. As you pull the hand lever out inside the car, it opens the butterfly plate to achieve the optimum air fuel mixture you desire to make the engine run smoothly. Sometimes you must go the opposite, lever out and plate closed, depending on the way the carb is set up, and work it the opposite way.

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1 Answer

I need to know how to check a automatic choke if it is working or not

Remove air filter, look down carb. Choke butterfly is on top. When choked, butterfly closes opening. When choke off, butterfly up, you can see the throttle butterfly.

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1 Answer

Rota Hoe Briggs and Stratton Engine

If the air fuel mixture is wrong, because main jet is locked or debris in the float chamber, that may cause inconsistent revs.

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1 Answer

Mower starts and runs but has no power acts like its flooding it burns a lot more gas can barley pull it self

Sounds like maybe the choke is stuck closed. If you remove the air filter the choke is the first butterfly valve you can see. The throttle looks similar but is a inch or so deeper into the carb, and you can't see that unless the choke is open. Try removing the air filter and starting the mower. It might run just a little better without the air filter since it will get a bit more air, but if the choke is stuck it still won't run right. But you will be able to see if that's the problem right off. If it runs great without the air filter, and the choke is not stuck, then the problem is a clogged air filter and you need to replace it. Good luck, Al K

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1 Answer

Hard to start n cold wheather put new battery in it still having trouble

I suspect the choke isn't closing fully. Remove air cleaner down to where you can see the choke butterfly. With the controls in choke position that butterfly should be completely closed. If not you can adjust it. If this is cable operated, adjust it by loosening the screw that holds it on the bracket and slide it until choke closes. This is done usually on carb end. I am also assuming it runs fine after start. Hope this helps.

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