14 HP Briggs & Stratton Carburetor Advice

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Old 05-22-16, 01:40 AM
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Question 14 HP Briggs & Stratton Carburetor Advice

Hi, I have been reading and learning from this forum since I began trying to bring my old riding mower back to life a few weeks ago. I have a 1998 MTD Yardman with a 14 HP Briggs & Stratton engine.The engine model number is 287707- 1224-E1.

The mower had been sitting for about 2 1/2 years since I ran the gas out of it at the end of the fall cleanup. It had been used in a very high dust area and I remember it had gotten very hard to start.

When I decided to get it running again I remembered how poorly it would turn over. It would turn over once strongly, but then not turn over again; or turn very slowly. After reading on this forum I realized the valves needed to be adjusted because the stater was cranking well with no spark plug in the cylinder. I did get the engine to start and run well with the choke left on for about 1 minute before it died.

After doing the valve adjustment the engine still only revolved one time. When I took out the spark plug, the cylinder was full of gas. I drained the gas, drained and changed the oil for the second time & decided it was time to clean the carburetor.

I went for the quick & lazy method on the first try. I clamped off the fuel line, took off the solenoid shut off & drained the gas from the bowl. After removing the bowl I saw it was the dirtiest bowl I have ever seen. I cleaned the bowl with degreaser and steel wool, but did not take the carb off. I sprayed carb cleaner at high pressure all around and through every orifice I could; then followed that with air from the compressor.

After that I put it back together and hooked up the gas line. Without even starting the engine I could see gas moisture appearing on the black plastic parts on the top of the carb. I dried it and blew it off with compressed air, but it returned almost instantly. I realized the carb needed much more work and would need to come off the engine. I removed the carb (still attached to the intake manifold) from the engine & the air cleaner assembly. There was a lot of gas in the intake area of the cylinder head. I used rolled up paper towels to dry up the gas from the cylinder head. I checked the new oil and no gas has yet leaked into the crankcase, the intake valve happens to be closed.

I have re-cleaned the carb and the needle valve looks pretty good for it's age. Time and budget-wise I would like to at least see if I can get it to run before I get a whole carburetor rebuild kit. But I do not want to take any avoidable chance of ruining the new oil again by flooding the crankcase with gas. I will be installing a shut-off valve in the gas line ASAP.

The most specific question I want to ask today is this: Can I test the seating of the needle valve to see if the carb is filling with gas before actually putting the intake manifold with attached carb back onto the engine? If I set, or hold, the carb & manifold level and hook up the gas line will I be able to tell if it is still filling & flooding the bowl, carb & intake manifold?

Any help to see if the needle valve is now shutting off the flow to prevent everything from flooding is appreciated. I just don't want to get it all back on the engine and have fuel filling the cylinder and ruining my new oil all over again. Thanks in advance for any help or suggestions.
 
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Old 05-22-16, 04:34 AM
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Can I test the seating of the needle valve to see if the carb is filling with gas before actually putting the intake manifold with attached carb back onto the engine?
Yes but you don't test it with gas. You test it with air. Blow through the feed hose. The air should move freely until you move the float to where the needle seats & it stops the intake. You won't be able to blow through the hose at that point.

That being said. It sounds like you have a problem of a gas washed cylinder. If the cylinder & the crankcase were flooded with gas, you have to change the oil & bring the compression back with a few drops of oil in the cylinder. Spin the engine a few times. If you don't change the oil, you'll be going in circles.
 
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Old 05-22-16, 08:13 AM
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On troublesome carbs like sounds to be your case, I will leave the intake connected, disconnect the breather inlet, and hang the carb on the studs leaving a gap between the carb and intake and connect the fuel line. It can take several minutes sometimes for a leaking needle valve to show up but if it does, this will keep fuel from getting into the intake and engine oil.
 
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Old 05-22-16, 01:12 PM
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I do the same thing as BFHFixit. Connect the gas line and see. You can't really test it with air because the gas sometimes leaks so slowly past the needle that it takes a long wait, even overnight sometimes to know if it's sealed or leaking. If there is no gas in the oil,you don't need to change it.

Get some gumout carb spray and soak a q-tip with it and clean the seat area really well multiple times. Make sure the sides and tip of the needle are clean as well. Make sure the float moves freely.
 
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Old 05-23-16, 08:28 PM
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Smile

Thanks, guys. I used the carb cleaner & q-tips, examined the tip of the needle valve again and put it back together carefully. I kept the intake manifold just a little off the mount to not draw gas in if it leaked. I also put a fuel line shut-off valve for control and protection. The needle valve did it's job this time and after letting it sit a couple hours with the gas on it was looking ok.

The motor started right up. It runs almost as well as I would expect for an 18 year old engine. It hesitates for a split second about once every 30 seconds. Before putting back on the plastic air filter housing with the filter there was a flash of fire popping back thru the carb with every hesitation. I will replace the plug soon, although I'm not sure what the most likely cause of the hiccup is. It did seem I had to keep more choke on while the motor warmed up; I think I used to cut the choke off much sooner in the past.

If there are likely causes for the mis-firing that's happening I would love to learn from your experience. Even if I am unable to make it better, it is still a huge improvement over over pushing a mower with my severe arthritis.

Apart from the engine, I was shocked at how much noise the old belt operated deck made during and after engaging it by lowering into cutting position. I had tried to oil as many movable parts as I could beforehand, but I will be trying to check it again soon.

Thanks to those who responded, I'm open to any further suggestions as well.
 
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Old 05-23-16, 09:07 PM
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With a name like Catfish you gotta be a good guy ~!~!

A mower that old you probly got a Walbro carb on that monster. Even if you don't your valve seat is probly bad. If you don't have a leak then you might be good.

Your surging might be from a very well clogged carb and I had issues with that here recently on quite a few. Welch plugs had too be removed and I soak mine in carb dip OVERNIGHT then spray with carb cleaner. Punch a new plug in and kit it adjust the low speed jet and you are good to go .. ~!~!

Those valve seats are a PITA too take out. They are pressed in there and made out of brass. Not the rubber seats like in a 5 hp bowl type carb. Your needle has a rubber tip on it.

Let us know later ~!~!
 
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Old 05-24-16, 01:24 AM
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The hesitation and pop are caused by some slight lean running from a bit of a restriction still in the carb. You can try cleaning it more or run ssome seafoam through the tank and see what happens.
 
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Old 05-24-16, 05:14 AM
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Do you have the Nikki carb?
 
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Old 05-24-16, 07:32 PM
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It is the Walbro LMT carburetor. I have a gallon of that super strong dip cleaner somewhere, but even if I could find it I probably wouldn't use it. About 8 years ago I took the carb off my 1969 BSA Victor Special, took it apart and put it in the cleaner. Unfortunately, I was smoking too much herbal medication & I forgot about it for a week. Needless to say, I ruined the carburetor I was trying to clean.

I do want to get some seafoam and run it thru the system. I won't be able to get to the store until Saturday, but if anything good or bad happens I will post it.
 
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