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B&S 16 HP riding mower not running right


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07-13-09, 12:20 PM   #1  
B&S 16 HP riding mower not running right

Model: 300707
Type:0136-E1

I rebuilt this carb(nikki carb) last year or maybe the year before and it has run fine until a couple weeks ago. A couple weeks ago I was mowing and when I disengaged the blades it started sputtering and died. I pushed it to the garage. The next day most all the gas dripped out all over the garage floor. Ended up the gas was flooding the carb. I took the spark plug out and gas poured out. I also had to drain the oil because gas got in there to. I was going to rebuild the carb again but the local mower service told me it probably wouldn't do any good because it had a Nikki carb and that type doesn't have a seat. I can only replace the needle. He told when the seat is bad the carb needed replaced. Someone told me I could put a shutoff valve before the carb and turn it on each time I mow. I did that and it seemed like it was going to run. Well, today I mowed for the first time since I put this valve on. It seemed to mow fine until I disengaged the blades. Then it sputtered but I turned the blades back on and it ran OK to get it back to the garage. Each time I disengage the blades or idle it the mower will start sputtering and die. Do I have to replace the carb. If I do I was told to get a Walbro carb to put on it this time.

 
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07-13-09, 04:05 PM   #2  
There is less chance the seat is beyond service than there is some trash, corrosion or other debris has gotten into the seat or damaged the needle tip....float not floating, vent plugged...
I have also seen mentioned in several posts about polishing the seat with a qtip ....

If you have kited the carb once it is certainly worth at least pulling it off and having a look, cleaning it up and maybe find something obvious.

 
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07-21-09, 02:41 PM   #3  
I took the carb off again and took it apart. I cleaned it up and blew carb cleaner in all the holes. The seat looked good but I took Q-tips and tried to polish the seat. I checked the seat with a magifiying glass and didn't see anything wrong with it. The needle looked OK except the tip looked a little crooked. Put it all back together and it still does the same thing. I mowed yard today but as soon as I shut the blades off and idled it the mower flooded and died. Do you think it would do any good to get another kit and rebuild it or should I just buy another carb?

 
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07-21-09, 03:10 PM   #4  
Is your float plastic? It would be rare but shake it and see if it sloshes.
Almost sounds like you may have a linkage hanging up or maybe the butterfly valve is hanging, check the screws on the throttle/butterfly valve see if they are loose and still there or if any damage is visible. Also make sure the choke stays open fully when not in use.

 
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07-22-09, 03:42 AM   #5  
I've already checked the float . It is good. As far as a linkage or butterfly valve hanging, would gas still flow when the motor is off? I've looked inside the carb as it's running and I see where the gas comes into the coarb through the nozzle in the bottom of the carb. I think that is where the needle is on the other end allowing the gas to come in. If I shut the mower off and also shut the gas valve off (I put an in-line shutoff valve before the fuel filter) no gas comes out of the carb. But if I turn the vavle on and wait a few seconds gas starts flowing out that nozzle and the motor isn't even on. It's possible that I don't have the linkage right but would gas still flow when the mower is off?

 
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07-22-09, 07:29 AM   #6  
The model numbers you posted do not produce any results on the briggs site so I can not view a breakdown.

You could have a plugged vent that would not allow the float to close the needle valve.
You can check to see if the needle valve will shut off fuel by removing the bowl with the carb in place, turn the gas on and raise the float by hand and see if flow will stop.

 
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07-23-09, 03:41 AM   #7  
Sorry--I had the model number wrong. It's 310707.
I took the bowl off and turned the gas on. Gas started flowing out the bottom. When I raised the float the gas flow stopped. Is there some adjustment to make on the float? I didn't see anyway of adjusting it.
Also I don't know if this makes any difference or not but I forgot shut the key off and I left the ignition key in the on position all night . When I went to unplug the solenoid on the bottom of the bowl it was pretty warm or hot from the ignition switch being left on all night. Would that be normal for leaving the switch on?

 
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07-23-09, 11:52 AM   #8  
Posted By: flyinghigh4 Sorry--I had the model number wrong. It's 310707.
I took the bowl off and turned the gas on. Gas started flowing out the bottom. When I raised the float the gas flow stopped. Is there some adjustment to make on the float? I didn't see anyway of adjusting it.
Also I don't know if this makes any difference or not but I forgot shut the key off and I left the ignition key in the on position all night . When I went to unplug the solenoid on the bottom of the bowl it was pretty warm or hot from the ignition switch being left on all night. Would that be normal for leaving the switch on?
If the key was left on then the solenoid was energized and draining on your battery so for it to be warm would be normal.
I do not think your float needs any adjusting, I think you may have a vent that is plugged and not allowing air to escape from the bowl to allow the float to raise.
The breakdown does not show a vent and I do not have a Nikki carb here nor am I in the shop today...oh and I have no memory, at least not a good one so I am not sure where it may be. The IPL does show one welch plug but not clear on where it is.
It should be accessible from outside the on the carb body. Small screw/jet, maybe under a plasitc cap or welch plug....might be able to soak the body in carb cleaner and open it up also.

 
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07-23-09, 02:49 PM   #9  
I sprayed carb cleaner into every hole I seen when I had it apart.
I just went out and looked on the carb for some numbers. Will this help you to find a diagram?

697216
G02703
4322 C

 
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07-23-09, 08:33 PM   #10  
On top of the carb body you should find a brass screw, next to it you might notice a small ball bearing or check ball indented in the body of the carb. If you remove the screw there is a jet inside. It will take a jewelers type screwdriver to remove. Best to clean or soak the body so that all of that gets cleaned. I don't know the exact schematic of it but I believe that jet and check ball vents the bowl.

 
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07-24-09, 04:59 AM   #11  
I took the carb off and took the screw out that was next to the little ball bearing. I didn't need a jewelers screwdriver to do anything. The screw had a black plastic cap on it and the screw has a spring on it. I just screwed it out with my fingers. The screw come to a point. Is that the jet you where talking about. There was nothing in that hole to take out after I took the jet screw out. I sprayed WD40 on the ball bearing and carb cleaner to clean it up. I put the carb back together. One problem. I didn't pay any attention to how many times I scewed that jet out so I'm not sure where to reset it to. Is there a certain setting for that? Seems like there would be. Anyways, I put the carb back on and turned the gas valve on. I was watching inside the carb for gas. As you are lookong into the carb when it is mounted on the mower there is two hole on the right side. One above the other. Gas started flowing from the top hole this time? Nothing come up from the nozzle in the carb this time.

 
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07-24-09, 07:16 AM   #12  
That sound like your idle mixture or idle speed screw not the one I am referring to. The one I am talking about does not have a spring and is screwed in flush with the body.
I will get a picture of the Nikki carb I have today.

If the screw you removed tapers to a point, then turn it in until it just seats or stops, then back it out 1 1/2 turns.

 
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07-24-09, 07:45 AM   #13  
Here is a photo from the Nikki corporate site of a typical carb. The one in this photo may not have a screw hiding the jet but is likely under the welch plug that is visible in the groove that the mounting bolt goes through. If yours is the same and is mounted on the engine, you may not be able to see it.


 
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07-24-09, 01:43 PM   #14  
Here are some photos of what is beneath the welch plug or screw if your carb has access.

First photo red is the screw, yellow line is the welch plug.

This image shows the screw removed and the jet backed out.



Lastly the jet removed, if you have this you can look in the cavity and see an orifice leading to the check ball also pictured.



If you do not have to apply great force on the float to shut off fuel flow, then I believe this is your problem. You can buy a new carb, soak the body as I have already mentioned, find someone who can do the work for you or buy a new tool.

My apologies if I have not offered correct or adequate information.

Good Luck!

 
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07-25-09, 09:41 AM   #15  
I couldn't figure out how to get a picture of mine on here. When I clicked insert image it ask for the URL of the image which I couldn't get anything to work. But anyways, mine doesn't have the screw. Only the welch plug. Can I pry the welch plug out or is the carb no good after I do that? If I can't pry it out I guess I'll go to town to get some cleaning solvent and soak it and try one more time before I get another carb.

 
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07-25-09, 11:30 AM   #16  
You can remove the plug but you will need to replace it. It may have come with the kit if you already have purchased one, 690727 is the briggs part number for the plug and the IPL does not show it included in the kit

Removing and replacing the welch plug does require some mechanical maneuvering and precision, or luck if you prefer.
I have not had one of these out on a Nikki so I can not tell you what lays under it. But it would or should allow you to clean and verify fluid can pass.

It would be best to try soaking the carb using a carb cleaner. If you use a dip type carb you should remove the plastic parts of the throttle and choke.

Depending on your ability and available time it might be a good idea to check price and availability of a replacement or even a used carb and weigh your options.

 
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07-25-09, 09:43 PM   #17  
I wouldn't remove the welch plug just yet as it isn't related to the problem you're having.

I'd say if yours has the white plastic assembly inside, remove it, then remove the needle and clean the seat area with a q-tip soaked with carb cleaner, then blow it all out well and reassemble. Seat failures aren't very common on that carb in my experience.


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07-25-09, 10:41 PM   #18  
Posted By: flyinghigh4 i took the carb off again and took it apart. I cleaned it up and blew carb cleaner in all the holes. The seat looked good but i took q-tips and tried to polish the seat. I checked the seat with a magifiying glass and didn't see anything wrong with it. The needle looked ok except the tip looked a little crooked. Put it all back together and it still does the same thing. I mowed yard today but as soon as i shut the blades off and idled it the mower flooded and died. Do you think it would do any good to get another kit and rebuild it or should i just buy another carb?
. .

 
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07-26-09, 09:58 AM   #19  
I went to town and bought a gallon of carb cleaner at the auto parts store. I'm going to soak it overnight and see what I have in the morning. I was telling the store clerk what my problem was. He said he had a B&S engine that did the same thing. He replaced the solenoid on the bottom of the bowl and that took care of the problem. Could that be possible?

 
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07-26-09, 10:30 AM   #20  
Oh, I missed the part where you used the q-tip. Still, I believe there is a problem in the needle and seat area. Does your replacement needle match the old needle? Does this nikki carb have the plastic guts, or metal? There were some of both types. The anti-backfire solenoid won't fix the problem.... it was just coincidence that it worked for him.


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07-26-09, 11:43 AM   #21  
It has plastic guts. I don't remember how the needle looked on the old one. It was either last year or the year before when I rebuilt the carb.

 
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07-26-09, 07:33 PM   #22  
On the nikkis with the plastic guts, the gasket between the carb body and plastic part can leak and overfill the bowl as if the needle was leaking. Also, the spring at the bottom should be intact and holding the plastic part up tight to the carb body.


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07-27-09, 06:14 AM   #23  
I soaked the carb overnight in carb cleaner. Put it together and back on the mower. When I turned the gas valve on gas started flowing out of the upper hole on the right side of the carb. Before I took out the idle mixture screw I thought the gas was flowing out of the nozzle coming up the middle of the carb from the bowl.
Cheese--the main gasket between the carb body and plastic part looks to be in good shape but there is an O-ring on the plastic part that looks alittle rough. As far as the spring being intact-- I don't have a sping inside the carb. Are you talking a spring in the bowl pushing up on the plastic part? The float would be in the way for that wouldn't it? When I put the 2 screws in the bowl and screw it onto the carb body wouldn't that hold the plastic part in place?

 
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07-27-09, 10:15 AM   #24  
That o-ring is the fuel inlet over the needle. If it leaks, the bowl will flood. Also, the spring is small diameter. Look at the bottom of the white plastic piece. See the 3 little stubs around the main jet? The spring fits inside these....they are there to hold it in place. I don't recall if they made any of these that don't use a spring.


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07-27-09, 12:02 PM   #25  
I don't have no spring down there. The three stubs on the bottom of the plastic piece looks like they bottom out or set on the bottom of the bowl. I see marks in the bowl where those three stubs were setting against it. Do you think that is how it's held in place instead of a spring. I look at a carb overhaul kit and I didn't see any spring that would go there. Here's the link to the kit:

https://www.mfgsupply.com/m/c/22-10932.html

Can I get just a o-ring somewhere and replace to worn one?

 
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07-27-09, 08:10 PM   #26  
Yeah, go to an auto parts store and match up an o-ring to yours. I'm trying to remember, it seems like I've seen some of these without the spring too, but I can't swear to it.


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07-28-09, 07:42 AM   #27  
Couldn't find a o-ring to fit right. A local lawnmower repair shop is ordering a gasket set for me. It's just the bowl gasket and the o-ring for $6. I won't get that until next Thurs so I'm on hold till then.

 
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04-07-10, 08:13 AM   #28  
I give up

OK-- I gave up on trying to get this carb working right. I'm going to replace it with the Walbro carb. Hopefully this will be better than the Nikki carb that is on it. The numbers I come up to order is 698620 & 791886. Prices on the Internet are $90-$124.00. Is this what I'm looking for?

Thanks Dave

 
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