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onan b48m DD carb troubles


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#1 Beardo OFFLINE  

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Posted June 26, 2017 - 10:54 PM

Hello, I recently picked up a 83 448. Thought I got a pretty good deal on it, picked it up for 500 bucks. Problem is it runs super rich. I got a carb rebuild kit with the fuel pump rebuild and brass float and I installed it. And it still runs rich. Tried adjusting the idle and power screws and they do not help at all. And when I say it's rich it's filling the ports with fuel. The kit I got did not come with a float assist spring, but I did check the float to see if it had any leaks. Does anyone have any idea what I should try next? I looked all over the web and couldn't find anything on this problem.
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#2 ssmewing ONLINE  

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Posted June 27, 2017 - 06:15 AM

Did it come with the new black plastic valve body for the pump?

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#3 stiemmy ONLINE  

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Posted June 27, 2017 - 09:12 AM

I would think the float is out of adjustment with an uncontrollable amount of fuel. Did you clean the needle and seat?
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#4 Oldford OFFLINE  

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Posted June 27, 2017 - 01:07 PM

Welcome to gtt.  sounds like a nice tractor.  post up a pic or 2 when you get the chance...



#5 Beardo OFFLINE  

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Posted June 27, 2017 - 01:16 PM

Yes I replaced the valve plate in the fuel filter. The float is to spec according to the manual. And needle and seat were replace when carb was rebuilt. Would they need to be cleaned before assembly?

#6 Beardo OFFLINE  

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Posted June 27, 2017 - 02:08 PM

Thanks oldford I will later on in the week. It's a little beat from the previous owner. But besides a bent axle and the flooding it is mechanically sound. I picked up a Johnson workhorse model 10 for 250 bucks I want to put on it. But figure I got to sort out the engine troubles first.

#7 ssmewing ONLINE  

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Posted June 27, 2017 - 02:47 PM

Yes I replaced the valve plate in the fuel filter. The float is to spec according to the manual. And needle and seat were replace when carb was rebuilt. Would they need to be cleaned before assembly?

 

No cleaning, but a trick is when the needle and seat are installed you hold the carb upside down and blow in the fuel inlet to check them before you put it back together. I am not sure that works with the DD carb though.

 

But, obviously, the needle and seat is the "switch" for fuel coming in or stopping it. It is not stopping it for some reason. So, that you will have to figure out.

 

You sound like you have plenty of experience. go back over your work. Something went wrong.



#8 dropped82 ONLINE  

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Posted June 27, 2017 - 05:46 PM

What style float is it? Brass or spongy type? It's possible the float could be full of fuel. The other type will break down and send pieces to stick the needle open. I have multiples of these and they're pretty simple. The fuel pump will not have the pressure to override the pump if the float and needle are doing their job.

Eric

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Edited by dropped82, June 27, 2017 - 05:46 PM.


#9 Beardo OFFLINE  

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Posted June 27, 2017 - 05:58 PM

I installed a brass float when I did the rebuild. I tested it for leaks before install. It originally had the sponge float in it. Maybe it's possible I missed a peice of debris from the old float during the cleaning process. Funny this is when it's running with the air cleaner off you can see fuel almost dribbling into the throat of the carb. I read on one of these posts to screw the idle and power screw till they stop. Then back them off 1.5 turns.

#10 ssmewing ONLINE  

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Posted June 27, 2017 - 06:53 PM

The screws at this point have nothing to coming out do with it. The fuel is coming out of the bowl. 100% not screws.

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#11 Beardo OFFLINE  

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Posted June 27, 2017 - 07:04 PM

Well arnt the screws the adjustment of fuel? When I got it the were turned almost all the way out. But I get what your saying they wouldn't cause the problems I am having.

#12 ssmewing ONLINE  

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Posted June 27, 2017 - 07:12 PM

The fuel bowl is open air. 2 things only control the fuel flow into the bowl. The needle and seat and the fuel pump plastic valve body. The biggest mistake many make is not replacing the valve body that the fuel line connects to and not replacing all the fuel line including the pulse line to the pump. 95% of carb issues are those things.

You can't get a read on adjusting the screws until you fix the first problem.

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#13 KennyP ONLINE  

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Posted June 28, 2017 - 07:22 AM

I put a brass float in my B48G and have had nothing but issues with it flooding. The float bends out towards the 'float' part and makes it flood. Like they made that part too thin!



#14 MH81 ONLINE  

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Posted June 28, 2017 - 05:06 PM

I got my float and needle from Doc. Roper carb has been issue free since.
I would say you're dealing with a float/needle issue, but it could be a sinking float.

Easy tests for a brass float.
You can hear the gas in it if you shake it.
You can hold it submerged in hot water and see the bubbles / gas coming out. Good way to find the leak.
Some leaks can be fixed... they require practice, a soldering iron, practice, lead free solder, practice, and an ice cube.
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#15 MH81 ONLINE  

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Posted June 28, 2017 - 05:08 PM

I put a brass float in my B48G and have had nothing but issues with it flooding. The float bends out towards the 'float' part and makes it flood. Like they made that part too thin!


Kenny, I think you may be right in the thin. You can help that by thick tinning the bending area with solder.
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