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B&G engine with Nikki carburetors #590400 replaces #796078


Norm201's Avatar
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05-22-14, 04:24 AM   #1  
B&G engine with Nikki carburetors #590400 replaces #796078

The idle mixture needle valve with cap-limiter broke off the carburetor, with the needle section imbedded into the body of the carb. A new unit will cost about $100. Any possible way of removing the broken section in the carb body? I think it’s too small for an easy-out extractor. Beside I only have hand tools at my disposal. Engine runs very rough and I'm fairly certain the air mixture is the main problem. That limiter screw was in fact adjusted many times in the past and is not in it's factory position.

Or is there another model that would fit the engine configuration? See photo’s at
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From the parts diagram

Ref # 1091 P/N 69133 Cap-Limiter part of ref# 94A P/N 793610 Kit-Idle Mixture

Total carb assembly Ref # 125A P/N 796078 superseded by 590400

 
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05-22-14, 07:20 AM   #2  
Do you mean a Briggs & Stratton engine?

EZ-outs come in different sizes so that is still an option.

I'm wondering why the idle mixture was frequently being changed? I'm wondering if you have something more serious than an out of adjustment idle jet. What does it do besides "run rough"? Does it run rough at all rpm's or just at idle? Does the engine surge? How is the oil level?

 
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05-22-14, 09:44 AM   #3  
I've had this happen. I use the blade out of a hacksaw and cut a notch across the top of the broken screw. You will cut into the carb body a little, but it doesn't hurt anything. Then you can use a screwdriver to remove it.


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05-22-14, 05:28 PM   #4  
Do you mean a Briggs & Stratton engine?

EZ-outs come in different sizes so that is still an option.

I'm wondering why the idle mixture was frequently being changed? I'm wondering if you have something more serious than an out of adjustment idle jet. What does it do besides "run rough"? Does it run rough at all rpm's or just at idle? Does the engine surge? How is the oil level?
This whole ball of wax goes back to a thread from last summer that I started but never responded as to the end result.
(See http://www.doityourself.com/forum/ou...ml#post2156937)
That's because it hasn't yet resulted.

Yes its a Briggs & Stratton. The screw is so small I doubt that I can get an EZ out into it. But I might try. The reason why it was screwed around so much is that I totally removed and took apart the carb this past winter to clean it. In the process it seemed to just fall off.

I may as well give you the whole story. This spring, after re-assembling the carb (even with broken limiter) I could not even turnover the engine with a battery charger on "start" mode. After checking things, I drained out about 3 quarts of gas from the oil sump. Put new oil in and borrowed a cheap compression tester and it seems OK. Put in new oil and no gas is seeping into the oil sump. (It's been about 3 weeks so far). After unfouling the plug and re-gapping the plug the engine starts just fine. I can get it to run smooth part of the time, but then any movement of the throttle will throw it into a rough mode blowing a mild black smoke through the muffler. Then I can fool with it and get back to a clean and smooth mode. It sounds like a fuel air mixture and several friends of mine have confirmed or a least agree. So that is where it stands at this point.

As far as the original problem goes from my first post referenced above, I have not resolved it yet. But a friend of mine has done some digging and it may well be the carb bowl piston wire getting too hot and shorting out or sticking open or the kill switch wire from the coil getting too hot and also shorting out. But that's minor to my current problem.

Of course the other problem is time. I only get maybe once a week for and hour or two to fool with the thing. This weekend is out because I'm camping with my son-in-law. Just us two away from the women and kids.

Cheese, by the way, I may well try your suggestion and file a slot in the body.

 
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06-23-14, 01:42 PM   #5  
Last word on this thread.

I finally got disgusted with trying figure what was wrong with this B&S engine on my Craftsman riding mower. I brought it over to a nearby backyard garage mechanic who has a variety of lawn mowers and small engine vehicles for sale on his front lawn. Typical hillbilly type guy but very nice. Has quite the reputation. Anyway he took it for about a week. Picked it up this morning in good running condition. He said he replaced the carburetor. Even though I had cleaned and rebuild it, he said it was not worth fooling with it. For $85 my mower is running fine.

I do have another question concerning this unit, but I'll start another thread and let this beast die a quiet death.

 
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