Rebuilt a carb, ran smooth, now runs rough, disappointing - Snowblower Forum : Snow Blower Forums
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post #1 of 17 Old 02-09-2017, 09:32 PM Thread Starter
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Rebuilt a carb, ran smooth, now runs rough, disappointing

I rebuilt a carb on a 10hp Tecumseh. The carb was in real bad shape sitting for years and partially outside, how long, I don't know. In Sept I bought a used 10/29 Craftsman that had very little use. You can tell from the scraper bar, skid shoes, and paint. What a nice machine with a 12" impeller, high front, very well balanced, like to say a dream to use but it is still a heavy machine to move around. Even when it's moving forward you know you have something powerful in front of you.

I took the carb apart including the small Welch plug on the side, soaked in Berryman's ChemDip for an hour in my ultrasonic cleaner, then turned the USC on for 60 minutes, let it sit for an hour and turned it on again for 30 minutes. Dipped it in water to clear out the solution. Sprayed it and the holes with compressed air. Used a torch tip cleaner through every hole. Blew it out again. Then reassembled with a new Chinese rebuild kit complete with welch plugs, low and high speed needle valves, rubber o rings, and washers.

Put the carb on the machine, started on the first pull. It ran so smooth, I didn't even need to adjust the low and high speed though I checked them. I ran it for about 10 minutes and it did not miss a beat. I turned it off and started it several times, always started with the first pull.

Today snow! Not much here in NJ, 3" but WET. I used a 5hp Noma to start with and then grabbed the 10 hp Craftsman to see how that worked. It started right away, ran smoothly, took it from the rear of the house to the front sidewalk and then it started running rough and kept dying. I kept restarting it and it ran rough and died. After 5 pull starts I checked the gas and it was empty. yea yea yea. No wonder it was dying. I put gas in it and it ran rough. While it was running I bled some gas from the fuel bowl using the spring relief valve in case there was water in the bowl and the same, ran rough. I grabbed another snowblower to finish the job.

What do I do? On a warm day I'm going to take the carb off, open the petcock and let some fuel from the fuel line into a clear soda bottle, let it sit and settle to see if there is dirt or water in the gas. I doubt it, the gas was gotten 2 days ago and used in 5 other snowblowers. Then take the carb completely apart and spray some carb cleaner in every orifice using those plastic red tubes attached to the carb cleaner, put it back together and see how it works again. If it fails to run smoothly, change the spark plug? Then put on a new Amazon carb I have! for this machine.

It does seem strange that it ran smooth the day I put the carb on for 15 minutes or so then the day of the snow it ran smooth until a few minutes later when I needed it for the front sidewalk. With being low on gas it seems like some dirt got into the carb and needs to be removed.

Any other suggestions?
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post #2 of 17 Old 02-09-2017, 10:18 PM
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No more rebuilds, slap a new one on there and be happy!
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post #3 of 17 Old 02-09-2017, 10:51 PM
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A torch tip cleaner in my book a no no. It will enlarge the holes you're cleaning and change the way the carb behaves.
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post #4 of 17 Old 02-10-2017, 08:59 AM
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Did your cleaning include that tiny little Atmospheric Vent Hole near the top of the carb body . . . . and that tiny Idle Control Hole at top of the threads on the brass Bowl Nut ?

When I say "tiny", I mean the holes that are about žMM.

Since you mention having old gas, these are spots that are quite susceptible to being plugged by incoming dirt in the fuel.

Got a Fuel Filter on that unit ?
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post #5 of 17 Old 02-10-2017, 09:24 AM
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Exactly, you have a few choices. Go through it again, be sure to clean every little oriface, and also make sure the line from the tank and the tank itself it in good shape. When they get varnished up, it usually takes a few good cleanings. Replacing the carb is really a good idea too...... they are cheap on ebay from China...... you may have to swap the choke lever/butterfly from the old one if the levers are different - and usually are.

I am deathly allergic to shovels!

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post #6 of 17 Old 02-10-2017, 11:36 PM
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The dirt and gunk gremlins got in there just to piss you off.Try cleaning again install a filter and hope for the best.
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post #7 of 17 Old 02-11-2017, 10:08 AM
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Just my opinion, but cleaning/replacing a carb without removing the tank and flushing and replacing the fuel line is a waste of time or at the very least a gamble. Let it run until it stumbles and shut it down, shut off the fuel and drop the carb bowl full. You probably will see little specs of black from the fuel line rotting away internally. You can pull a new line in without removing the recoil housing.
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post #8 of 17 Old 02-11-2017, 10:43 AM
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As jyclays says, I always replace the fuel line when rebuilding a carb. Ethanol eats at rubber and small chunks will break loose and clog a carb. I have a 25ft roll of fuel line on had all the time.

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post #9 of 17 Old 02-11-2017, 12:20 PM Thread Starter
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I believe in small cheap motorcycle filters from Amazon or eBay, and no, this does not have one. I did remove and clean the gas tank, and replaced the fuel line prior to installing the carburetor. I'm a believer the fuel bowl tells alot. At least, (sad), no snow in NJ for the next two weeks so plenty of time.
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post #10 of 17 Old 02-11-2017, 01:01 PM
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I always check the price of a new carb before I mess with rebuilding. In most cases the cost of the kit isn't much different than a new carb. I hate to be part of the throw away society but in my case I've have very good luck with the China carbs compared to me rebuilding them.

You might need to clean it again and this time get one of those filters in there before firing it up to protect your work.

Make sure the windows are up before the snow plow goes by !!

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