Starved for air - Craftsman 21hp B&S v-twin

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  #1  
Old 06-06-15, 11:30 AM
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Starved for air - Craftsman 21hp B&S v-twin

I've got a DYT 4000 Bob Vila edition with a 21hp Birggs and Stratton engine. It's been running great but today, in the middle of my cutting, the engine just quit. It stopped like I had run out of fuel...

Being on an incline, I thought I might be out. Added a gallon and it would only crank. I pulled the air filter off, and it started right up. Replaced the air filter and it now starts, but there's no power. I give it more throttle and it smokes and wants to flood out. I pull the filter off and it runs fine. So I know it's some kind of air restriction.

What do I need to look at? How do I get access to the carb without pulling every nut and bolt off this thing to get to it? Could it be the butterfly is sticking and a little carb cleaner might do the trick?


Thanks!
 
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Old 06-06-15, 12:24 PM
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Tried changing the filter?
 
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Old 06-06-15, 06:01 PM
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Sure did change the filter... I've also checked to make sure it's getting spark on both side and replaced the plugs... And based on the smoke it's getting plenty of fuel...

Now here's a new twist... The air filter is getting soaked in fuel, causing it to clog. So what would cause the gas to come up out of the carb to soak the air filter?
 
  #4  
Old 06-06-15, 07:28 PM
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I'd guess your needle valve is not shutting fuel flow off properly, or something is causing excessinve spitback through the carb. Do both cylinders have good compression? What engine is on this?
 
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Old 06-06-15, 08:55 PM
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Cheese,

This is on a 21 hp B&S Vangard or the likes... the sticker on the engine says Family: 5BSXS.7242VF 276023

BTW, I don't have the tools to test the compression. Can you tell me what I would need. Additional tools are always a bonus, if they can be had cheap enough.
 
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Old 06-06-15, 09:12 PM
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Cheese... I found a low cost compression tester @ Harbor Freight and there's one not far from me... Looks like I'll be heading there tomorrow to pick one up. Can you tell me what range it should fall in ... dry and west tests?

Thanks!
 
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Old 06-06-15, 10:00 PM
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I'd just check for compression in general, as in does one cylinder have compression and the other not? You can test that with a finger over the plug hole.

The engine model number should be stamped on a valve cover. I'm guessing this is an intek rather than a vanguard?
 
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Old 06-07-15, 04:42 PM
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Cheese,

I picked up a compression test kit (HF price was excellent!) and ran it. Compression is good on both cylinders and I noticed something.. It seemed as though there wasn't much fuel making it to the right cylinder. This is based on how the plug looked and now knowing I can start the motor on one cylinder by disconnecting the right plug, but not the left... Oh, I have an inline spark plug tester, so I know the coil is firing..

I'm not really familiar with carbs (never rebuilt one), but could the carb be starving the one cylinder of fuel, causing it to spit the gas out or would it more likely be a valve?

Oh.. and it is an Intek... Vanguard is Kohler.

Thanks!
 
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Old 06-07-15, 06:08 PM
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Vanguard is Briggs, so is intek. I need to know what engine we are talking about because my advice will be different for different engines. Briggs had many different 21 hp twin cylinder engines. Model number please.
 
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Old 06-07-15, 06:54 PM
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Sorry I can't get it right now because it's dark, but based on the Sears model number, it's showing it had a Briggs and Stratton engine model # 407577-0284-E1

If you still need to pull the cover off, and get it off the valve cover, I can do it tomorrow evening.

and THANK YOU VERY MUCH!!
 
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Old 06-07-15, 07:17 PM
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Ok, that engine has a single barrel carb (some of them have 2). Does applying partial choke make the engine run better? What were your compression readings and how did you perform the test? Also, check the oil. Is it thin, overfull, and/or smell like gas?
 
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Old 06-07-15, 07:31 PM
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I'm really surprised it's a single barrel carburetor two... I'm definitely going to have to pull the numbers off the valve cover tomorrow evening...

Partial choke makes no difference. Compression was @ 130 on both side +/- 2 psi from what I remember. I put the gauge in the spark plug hole and cranked it a few times, so it was a dry test. Oil was on the low side, and no hint of gas from it.

BTW, about two months ago, when I was mowing, the engine didn't feel as strong as in the past, but was running fine... When it did die, rpms dropped down and conked out like it was running out of gas.
 
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Old 06-07-15, 08:09 PM
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I woul hve guessed carburetor problem, but if choking it makes no difference at all, then it's something else. Maybe fuel flow to the carb.
 
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Old 06-07-15, 08:13 PM
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Thanks! I'm going to pull the cover off to make sure the engine id is correct. If it is, I'm going to replace the carb and the fuel line to see what happens... If it's a different engine, I'll let you know to see what you might think.. If not, I'll let you know what the new carb does...

Thanks again!!
 
  #15  
Old 06-13-15, 06:23 PM
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Rebuilt the carb and it's not the problem. I think it's missing a push rod. That's based on what I've seen others post around about one cylinder not working...

Now here's the thing.. My old Craftsman was beat up pretty good (I used it like a garden tractor for a couple years before I bought a CUT)... and I have had to keep putting $$ into it every year... I put 2 new tires on it recently... I'm nervous that it's going to die for good on me.. Because of this, I went and bought a new Husqvarna YTH24V48 today. Lowes told me if I changed my mind I had 30 days to bring it back and my grass hadn't been cut for 2 weeks in the back...

This new mower is the cat's MEOW!! Cut's even, super quiet and it's FAST! I think I'd be able to cut my mow time in 1/2 with it. Did I say it was FAST???!!!

Sorry for rambling ... but man do I like this new mower.. I don't think it's built as well as my old Craftsman, which was also an APY product, but man is the new mower refined... and FAST!

Ok... back to my old 21hp B&S.. Can anyone tell me how hard it is to replace the push rod? What should I look for when doing it .. a bent valve, or anything? If there is a problem, when should I throw my hands in the air and just junk it for parts?

Thanks!
 
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Old 06-13-15, 08:36 PM
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Why do you think a push rod is missing? It's very easy to replace a push rod. 10 minute job. I don't know what you would look for until you find out what happened to the old push rod. If it's missing, you will want to find it.
 
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