Tecumseh HM80 Carb rebuild

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  #1  
Old 05-23-10, 09:47 AM
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Tecumseh HM80 Carb rebuild

Inspired by my success at fixing my tiller following advice I got here, I decided to try to get my neglected chipper running. I left it sitting too long with gas, and the carb is a little plugged up with varnish. (Bad owner gets rewarded with an interesting project.)

I took the carb apart to find the inside of the bowl and float covered n varnish. I cleaned at them with some very fine steel wool and got them looking half decent. I also cleaned the insides with spray carb cleaner, and a small copper wire to open out all the holes. The main adjustment had a rusty tip, which I cleaned with steel wool. It is now clean, though not perfectly symmetrical. The welch plug inside was also covered in rust, which I have managed to mostly clean off though there are some spots on it. Lastly I tried to get air to pass through the needle seat. I was unable to blow through it, so applied some air from my compressor. The seat promptly flew out of the carb and disappeared across the garage somewhere.

Graduated from cleaning to my first rebuild. Since I now have to order parts, I went ahead and ordered a rebuild kit.

My questions are:
1. Should I pull and replace the now slightly rusty welch plug?
2. Assuming the recommendation is yes, how do I remove it?
3. Can I avoid this problem by running stabilizer all the time? Any negatives other than the cost?
 
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  #2  
Old 05-23-10, 12:07 PM
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You do not need to remove the welch plug if you soak the carb in a carb cleaning solution. If you have varnish on the float, you have varnish in ALL the tiny pinholes inside the carb. Soaking will clean those holes.
I assume this is a Tecumseh engine. If so, shake the float and listen for a sloshing sound which means there is a pin hole in the float allowing gas to fill the float. Tecumsehs are known for their floats filling with gas. Oh, and don't hold the float under water to see if it fills up. It won't. Water is too "thick" and will not seep into a pinhole where gas will.
 
  #3  
Old 06-15-11, 11:35 AM
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Join Date: Mar 2011
Location: USA
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I have the same engine and just cleaned the carb. Some of the varnish can get into a check valve that you cannot be cleaned(just right of center here);




Make sure to clean this:


The needles on mine were gummed up bad. My float also had a leak. i cleaned it out by burning it off with a propane torch and tried to reseal it with solder and then then super glue all over the float.

It has been working for the last 2 days. I suspect that it will die shortly and i will have to get a replacement. However, i now know the engine works (I bought the chipper used) so am very happy with this.

PUT IN A FUEL SHUTOFF VALVE! As the float fills with fuel it will open the fuel inlet and dump the tank of gas. Which is only a good idea if you want to submit an insurance claim for a housefire.
 
  #4  
Old 06-15-11, 12:00 PM
Join Date: Jan 2007
Location: MA
Posts: 514
raking, post your engine numbers so we know what we are talking about. Agree with Indy no need to remove welch plug inside carb but depending on carb may have a smaller one on side that should be removed. Use mini chisel or very carefully pierce with drill bit and simply pry out. To install new one simply put in place and lightly punch to expand it to seal. A quick coat of nail polish will also help seal. Regarding previous post I would not recommend to anyone soldering a copper float as there is gas in there and it can explode by heating with a torch. Cheap enough to replace and keep all hair ! For reference sake the above picture is from a newer emissions carbs and the older ones will look much different.
 
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