Smokey Techumseh 5 hp


Old 05-26-04, 06:42 AM
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Talking Smokey Techumseh 5 hp

Hi There

I have a 5 hp Techumseh on a troybuilt horse roto tiller. It is prob 20 years old, but only gets used three or four hours a year, so I don't think it is worn out.

It starts and runs very well, but after about 10 mins hard work will burp and belch blue smoke, then clear off, then do it again in five mins. The dealer said the air filter was plugged, so I gave him my hard earned for a new one, but have the same prob.

I have taken off the little crankcase ventolator do-hickie and it looks OK, the spring valve is in place etc.

Any ideas?

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Old 05-26-04, 07:30 AM
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Join Date: Oct 2003
Location: Davenport, Iowa
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If I had a single guess as to your problem it would be:

Sticking float in the carburator.

I have a Troy Built machine just like it here that my wife
uses in our garden. If it started doing what you described
that's what I'd check first.

The blue intermittant smoke may be the machine running rich because
the float doesn't shut the gas off flooding the carburator.

I suppose that you could have sticking piston rings as well but that would
be harder to check. My policy is to check the quick & easy stuff first.

Working a machine only a few hours a year can be harder on it if you don't take steps to preserve it between run times.
Old 05-26-04, 08:03 AM
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Thks Jughead


The carb is OK, this is definately oil getting pushed through the crankcase vent into the carb.

The stuck ring thing had occurred to me too, so I used Bardhal which usually frees them, but the compression has always been good and it starts and runs so well, I can't think it is blowby.

I am wondering if it is a problem with the crank vent, but I can't see anything wrong there (but am not sure what to look for). It seems like oil is getting past the reed valve, then building up in the hose to the carb, and every once in a while just burping a batch of oil in there.

What is the purpose of the reed valve? To keep pressure in the crankcase or to keep outside air out? What of I drill a small hole in the plate that holds the reedvalve to let the oil drain back into the crankcase?

Old 05-26-04, 01:15 PM
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Location: Davenport, Iowa
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OK, if you feel that the carb is in good order then consider a couple of other possibilities.

You could, indeed, have something going on with the crankcase breather system. The idea of the reed valve is to maintain the crankcase at a small negative (relative to the atmosphere) pressure. When the piston decends the volume inside the crankcase rapidly decreases which compresses the air, oil mist, and spend exhaust gasses. There would be a rapid increase in crankcase pressure when this happens if the pressure wasn't relieved by the reed valve. A small screen in front of the reed valve should cause any entrained oil to collect and that oil should drain back to the crankcase via a drain hole. Of course the other side of the breather reed valve should be connected to the carb via a small air line.

Now back to your possible problem. If you didn't have a small mesh screen in the breather and/or the oil drain hole was plugged I could see how you could get excessive oil flowing back to the carb via the breather line. Increased pressure inside the crankcase will tend to cause the oil to migrate toward the combustion chamber and can be the cause of excessive oil consumption due to leaking shaft seals and the burning of oil in the combustion chamber.

Given your description of the problem I would expect that the engine oil consumption would also be excessive and you would have some fouling of the spark plug.

The intermittant nature of the problem doesn't point toward defective valve guides, but that's another possible entry point of oil into the cylinder. Valve guides, like piston rings, don't tend to cause intermittant problems like you described.
Old 05-27-04, 12:25 AM
cheese's Avatar
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Join Date: Jul 2001
Location: USA
Posts: 16,817
Hello Polluter!

The breather could be hanging up causing the oil consumption. Also, check the oil. If it is too full, it will do this. Also, if it is thin and diluted (with fuel from a seeping carburetor), it will cause this.

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