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1850 Carb problems

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JonM in IN

05-12-2002 15:02:29




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I have an 1850 that is giving me carburetor fits. I have been having problems with it not being able to idle it down below about 1000 rpm and had a number of people rebuild it to no avail.... I could have lived with that, but I also have a problem where the throat will fill up with gas if it sets. Normally I could pull the air cleaner hose off and dry up the gas, and she would fire right up. Well this spring I tried to get it to start and just by turning it over, gas pours out the throat of the carb... I can't even get it to fire, as it floods itself with gas so quickly. Anyone got any ideas?? I guess the float is sticking open, but before I tear into it AGAIN, I want to get your opinions. I am ready to just fork over the cash for a new carb to hopefully solve all my problems. Does anyone know of a good source for rebuilt or new carburetors?

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Bob M

05-15-2002 11:09:47




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 Re: 1850 Carb problems in reply to JonM in IN, 05-12-2002 15:02:29  
Jon - I've encountered similar problems with our 1850, also with a 1750. Both have the Marvel-Shebler aluminum carbs. From my experience here's a few things to check:

1 - The fuel system on these tractors is originally equipped with an auxiliary solenoid-operated fuel shut off valve in the gas line between the tank and the fuel pump. Purpose of the valve is to shut the gas off whenever the ignition is off and prevent fuel from leaking into the carb bowl past the hard-tipped float needle. If this valve not working or is missing, recommend replacing it with a new one. Or you can simply shut off the fuel at the sediment bowl just before you shut down the tractor to prevent it from flooding.

2 - Check the carb body for dents/cracks. Seems the previous owner of the 1750 was prone to giving the carb a few whacks with a hammer every time it gave him trouble. Several years of this treatment resulted in a couple cracks to appear through float bowl casting. Cleaning thoroughly and filling the cracks with good epoxy cured that problem.

3 - When you rebuild the carb you MUST also replace the accelerator pump diaphragm (diaphragm's on the back side of the slanted cover.) Even if the diaphragm looks good it seems to develop pin holes and cracks which causes it to leak gas into the carb airstream and mess it all up. The diaphragm is not supplied with the basic rebuild kit. Instead it must be ordered from the dealer or a carb shop.

Hope something here helps...

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KMcMillan

05-13-2002 12:06:06




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 Re: 1850 Carb problems in reply to JonM in IN, 05-12-2002 15:02:29  
Had same problem with 770. Old mechanic said to try marvel mystery oil at 1 pint per 5 gallons gas. The darn thing stopped leaking, now runs great! Good luck



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JonM in IN

05-13-2002 14:29:34




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 Re: Re: 1850 Carb problems in reply to KMcMillan, 05-13-2002 12:06:06  
Thanks for the reply. I don't know if that would work for me or not. The old 1850 uses a good bit of fuel and I could probably pay for that new carb pretty quick buying 4 pints of oil per fill up. I might give it a try though just to get her running.
Amazing what these good old mechanics come up with. I once took my car to an old guy that did mechanic work. My car was smoking really, really bad. He said, "Hell, as long as it's smokin', you know your going somewhere!!" I guess he was right.

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CHRIS

05-13-2002 07:36:06




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 Re: 1850 Carb problems in reply to JonM in IN, 05-12-2002 15:02:29  
Is your needle steel tipped or rubber, I've had problems with the steel tipped ones and once I found a rubber tipped one, problems were over. good luck



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JonM in IN

05-13-2002 14:09:24




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 Re: Re: 1850 Carb problems in reply to CHRIS, 05-13-2002 07:36:06  
Mine are steel tipped. Where did you find the rubber tipped?



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Wrenchbender

05-13-2002 07:14:03




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 Re: 1850 Carb problems in reply to JonM in IN, 05-12-2002 15:02:29  

Is your carb made out of aluminum or cast iron? if you have the alum. one there is a accelerator jet inside the carb that has to be removed before cleaning. This would cause it to idle badly if the rubber seat has been damaged by cleaning. this jet is no longer available, so I've been told. Do you have an electric fuel pump added? If so the pressure may be too great for the float to overcome and will not shut off the flow of gas. Good luck, WB.

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JonM in IN

05-13-2002 14:14:51




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 Re: Re: 1850 Carb problems in reply to Wrenchbender, 05-13-2002 07:14:03  
The carb is aluminum. Yes it is possible that it is damaged. I first tried cleaning it by removing as few parts as possible. The carb cleaner may have damaged the rubber seat. I will have to take it all apart and inspect very closely. As far as the pump, it is still the mechanical pump. BTW, which carb is better, the cast or the aluminum? I've been told both ways, some say the aluminum is better and to hang on to mine, and others have told me that the aluminum wears and all you can find now is cast.

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Wrenchbender

05-13-2002 19:29:27




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 Re: Re: Re: 1850 Carb problems in reply to JonM in IN, 05-13-2002 14:14:51  

Both carbs have their good points. The cast one is a Marvel/Schebler and is simple and easy to rebuild. The aluminium is more difficult to rebuild but has an accellerator that has better performance. The jet I was talking about in the previous post is pressed into the carb. It is a one-way valve of sorts. If you get a repair manual it will show how it is to be installed. If you look done the throat from the top you will see it. It is brass and about 1/8" in diameter and has a slot in it that should be at a slight angle. It is removed by taking the float cover off and pushing it out with a pin punch that just fits the bore it is in. Once removed use your mouth to see if the one-way valve is working. If not you have found some of your problem. John deere also uses this carb on 30-4020s. If I get to the jd dealer in the next day or two I will check on parts availabiliy. WB.

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Ryan

05-12-2002 19:11:12




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 Re: 1850 Carb problems in reply to JonM in IN, 05-12-2002 15:02:29  
I have seen a similar problem, the flooding while sitting one, on lawn mowers when the vent line gets plugged. Not familiar with that carb, but thought any help is better than "it could be a dozen thin "



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jerry gerthofer

05-12-2002 15:33:31




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 Re: 1850 Carb problems in reply to JonM in IN, 05-12-2002 15:02:29  
i would say your float needs a little fine tuneing. or try a needle and seat kit should not be that big a dea



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JonM in IN

05-12-2002 15:46:20




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 Re: Re: 1850 Carb problems in reply to jerry gerthofer, 05-12-2002 15:33:31  
I hear what you're saying, but I've put in 2 rebuild kits in it already and had 2 reputable mechanics each rebuild it. The needle and seat that's in it is less than 2 years old. Is it possible that it's just shot... I guess I'll pull it off and take it apart and clean everything up real good. Better to even try another $20 needle/seat rebuild kit, than $400 on a new carb. Do you think the needle and seat would cause it not to idle down?

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jerry gerthofer

05-12-2002 16:36:54




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 Re: Re: Re: 1850 Carb problems in reply to JonM in IN, 05-12-2002 15:46:20  
no this would only take care of the flooding problem.linkage moveing freely. buttery fly sticking in carb? any thing binding????? could be a dozen thin



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