Lawn mower question

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17,980
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NH
So I picked up a well-used riding mower, 13hp OHV B&S engine. Came with a dead battery, no surprise there. While looking it over I went to remove the dipstick, just to see what would happen--the seller indicated it wouldn't run that way, and sure enough, it bogged down. I overlooked that fact... maybe I shouldn't have. Should these motors run with the dipstick out? The 10hp or flathead in my Toro will run happily with it out, splashes oil out so it's not wise to do, but it doesn't care.

Have to ask as this new-to-me mower refuses to start for me today... First it was full of gas, hydro-locked full (didn't think to turn the gas off last night, my old mower doesn't have a shutoff). Got it blown out but it just keeps flooding and won't hit. I did drop the bowl and the both shutoff and the needle/float seem to work; maybe the float is full, didn't think to check that, just thought of it now actually... Got spark, and after a few cranks it was over 140psi on a compression gauge. Bit of a project at the moment. Anyhow, it looks to me that the crankcase just ventilates to the air filter (and not to the carb, like for some pushmowers for lifting fuel), so I'm thinking, maybe it just plain has more blowby than I thought and is just plain knackered out.
 
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2,038
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South Central PA (Fulton Co)
First, yes the mower should be running fine with the dipstick in. They're meant to be installed while running.

Second, sounds like you need a new carb. I had a similar 13.5HP OHV Briggs on my old Craftsman mid-engine and had carb issues. Wouldn't rebuild well at all and I finally bit the bullet and replaced the entire thing. Been running fine ever since (4 years). Unfortunately it is one of the more expensive ones as it cost me about $120 shipped. But it was a small price to pay to never have to mess with it again. Came with everything I needed (gaskets and fuel shutoff).
 

supton

Thread starter
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17,980
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NH
No, I meant, it won't run with the dipstick removed--it would bog down.

Edit: from what I've read, quick glance while jogging around the honey to-do list, is that these single cylinder engines do need a bit of vacuum to run properly, otherwise they tend to consume oil. So the dipstick should be installed, and might not like running without it. It's just that, in this case, it immediately is impacted.

Edit 2: I hope I don't need a $120 carb, that would be more than the mower is worth... maybe a good investment, but not what I want to spend just quite yet! maybe later I can pull the bowl again and see what the float looks like.
 
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Messages
35,696
Location
NY
No, I meant, it won't run with the dipstick removed--it would bog down.

Edit: from what I've read, quick glance while jogging around the honey to-do list, is that these single cylinder engines do need a bit of vacuum to run properly, otherwise they tend to consume oil. So the dipstick should be installed, and might not like running without it. It's just that, in this case, it immediately is impacted.

Edit 2: I hope I don't need a $120 carb, that would be more than the mower is worth... maybe a good investment, but not what I want to spend just quite yet! maybe later I can pull the bowl again and see what the float looks like.
The dipstick should be in while running the engine. Regarding the carb I had a similar issue with a 15HP Briggs powered generator I was given. I made sure I had fresh fuel in the tank, with a good dose of Berryman's B12 in it. I dropped the bowl, went crazy spraying everything I could access with carburetor spray cleaner. Then I put it together and ran it on the lawn [which is more dust free than my driveway] without the air filter and between fanning the choke and spraying into the carb I got it to run nicely after about 5 minutes. I then changed the oil and fast forward about 6 months it is running fine. If you need a carburetor I would use a cheap knock off, vs a $120 carb. I've had good luck with them over the past few years servicing OPE for friends, and OPE I found, fixed and sold.

Having said that make sure the float is not cracked and loaded with fuel.
 
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2,038
Location
South Central PA (Fulton Co)
No, I meant, it won't run with the dipstick removed--it would bog down.

Edit: from what I've read, quick glance while jogging around the honey to-do list, is that these single cylinder engines do need a bit of vacuum to run properly, otherwise they tend to consume oil. So the dipstick should be installed, and might not like running without it. It's just that, in this case, it immediately is impacted.

Edit 2: I hope I don't need a $120 carb, that would be more than the mower is worth... maybe a good investment, but not what I want to spend just quite yet! maybe later I can pull the bowl again and see what the float looks like.

Not sure why I went with the expensive carb, but I'm pretty sure I could not find a Chinese knock-off at the time. Just looked and now they offer a couple for around $15-$20. Lucky me I guess...
 
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856
Location
Daytona Beach
The dipstick must be in the engine and no air leaks to the block. The pulses of vacuum/pressure from the piston moving down actually make the fuel pump work. If you follow the hose from the fuel pump you'll see it goes straight to the block or valve cover. Since you ran it with the crankcase open, before I'd put a bunch of money into a carb, I'd take the fuel pump apart and make sure the rubber flappers are in the right place and not "flipped" or folded. There are also valves in that fuel pump that could be leaking through causing your engine to flood.
Keep in mind I don't know this exact engine, but that same thinghappened to my neighbor and I fixed him up that way at no cost.
 
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2,038
Location
South Central PA (Fulton Co)
The dipstick must be in the engine and no air leaks to the block. The pulses of vacuum/pressure from the piston moving down actually make the fuel pump work. If you follow the hose from the fuel pump you'll see it goes straight to the block or valve cover. Since you ran it with the crankcase open, before I'd put a bunch of money into a carb, I'd take the fuel pump apart and make sure the rubber flappers are in the right place and not "flipped" or folded. There are also valves in that fuel pump that could be leaking through causing your engine to flood.
Keep in mind I don't know this exact engine, but that same thinghappened to my neighbor and I fixed him up that way at no cost.

I doubt this single cylinder has a fuel pump, most likely gravity fed only.
 

JTK

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13,449
Location
Buffalo, NY
If this machine uses a pulse/vac driven fuel pump, I can maybe see it not running right with the dipstick or oil fill cap removed.
 

supton

Thread starter
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17,980
Location
NH
No fuel pump. It's a B&S 28N707 series, FWIW. Pulled the air filter off, pic below. Crankcase pipe just goes into the base of the air cleaner.

Cannot remove the float easily, it's a plastic hollow float, but it's like the pin is staked in or something. Plus the bolts that hold the carb in are like 7.5mm? 9/32's is too small and 5/16's too big, 7mm too small and 8mm too big... Someone got into the motor at some point, as the bottom half is RTV'd, as is the screw on the carb bowl; which is kinda odd as the gaskets on the intake (carb to intake manifold) are still cardboard, so they must not have full torn apart. Dunno.

Getting late for today so will pick up again some other time.

carb1.PNG
 

supton

Thread starter
Messages
17,980
Location
NH
Do some of the modern engines have some sort of electric feedback, or just shutdown? I did a quick look to see about rebuild kits; unsurprisingly, cheap carbs abound. But when I look up 28N707 I keep get carbs with an electrical connector in the bowl area. What is that?

Example
 
Messages
35,696
Location
NY
No fuel pump. It's a B&S 28N707 series, FWIW. Pulled the air filter off, pic below. Crankcase pipe just goes into the base of the air cleaner.

Cannot remove the float easily, it's a plastic hollow float, but it's like the pin is staked in or something. Plus the bolts that hold the carb in are like 7.5mm? 9/32's is too small and 5/16's too big, 7mm too small and 8mm too big... Someone got into the motor at some point, as the bottom half is RTV'd, as is the screw on the carb bowl; which is kinda odd as the gaskets on the intake (carb to intake manifold) are still cardboard, so they must not have full torn apart. Dunno.

Getting late for today so will pick up again some other time.

View attachment 29257
You can pick that carb up for next to nothing. I would go with a knock off.
 
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5,280
Location
Ohio
Rarely will you see a pump if the tank is on the engine and higher than the carb.There's not much to go wrong with a float type carb. Pull it off the engine and check the float and clean the carb up. I have found many times is the fuel will cause pits on the pin which acts as the hinge for the float. It will hang up at times. I just use fine emory cloth the smooth it out and reinstall. Make sure the float needle is in good shape. Count the turns out that the mixture screws are set at and after cleaning, reinstall them the same number of turns out. I would rather rebuild an original carb than put a Chinese piece of junk on my engine. While you have the carb off, make sure the breather is clean and use new carb gaskets.
 
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supton

Thread starter
Messages
17,980
Location
NH
Rarely will you see a pump if the tank is on the engine and higher than the carb.There's not much to go wrong with a float type carb. Pull it off the engine and check the float and clean the carb up. I have found many times is the fuel will cause pits on the pin which acts as the hinge for the float. It will hang up at times. I just use fine emory cloth the smooth it out and reinstall. Make sure the float needle is in good shape. Count the turns out that the mixture screws are set at and after cleaning, reinstall them the same number of turns out. I would rather rebuild an original carb than put a Chinese piece of junk on my engine. While you have the carb off, make sure the breather is clean and use new carb gaskets.
I wasn't able to get the carb off, but the pin on the float was not coming out--not sure if it was pressed into place or what. I gave it a light rap but it was not moving. Do they press into place these days, on the cheaper carbs?

Carb has "Nikki" on the side so I'm thinking it might have been replaced once already.
 
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6,480
Location
Connecticut
I wasn't able to get the carb off, but the pin on the float was not coming out--not sure if it was pressed into place or what. I gave it a light rap but it was not moving. Do they press into place these days, on the cheaper carbs?

Carb has "Nikki" on the side so I'm thinking it might have been replaced once already.

Nikki is an OEM for Briggs carbs on those engines. The needle seat is pressed in (usually brass) but the pin should move freely. There is a kit that includes instructions and a new seat for those carbs. I think it comes with a self tapping screw and a piece of plastic to help pop out the seat and install a new one. Do you have the spec number for the engine? I saw you posted the model number further up. If you post all the numbers I can look it up for you when I have a minute, that kit will fix the flooding issue, which is what is filling the crankcase and preventing it from starting.
 

supton

Thread starter
Messages
17,980
Location
NH
Not sure on the carb p/n but it's a
Model: 28N707
Type: 37 01
Code: 9401104B

carb2.PNG


It's for an old Yardman I picked up over the weekend, a model 13357 that I think is from 1989. I've been wanting a bagger to try out.
mower1.PNG
 
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3,253
Location
USA
Look at where the carb meets the intake pipe. Is there a gap there? It kind of looks like entirely the wrong carb for this engine. Also two attachments to the choke lever -- someone has been doing a lot of tinkering.
 
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