Tecumseh HS50 key trouble

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Sep 24, 2021
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I just bought an old snow blower with a HS50 engine. It runs on, but I replaced the carb and throttle spring and I am having surging issues, but that is for another thread.

The issue here is the engine will run with or with out the key inserted and will keep running if I pull the key-
and I have trouble getting the engine to shutoff- I pull the key and nothing happens, the engine keeps running, and will also run if the wire from the key is not attached.
 
The key, and the wire are only to ground out the ignition to shut off the ignition. Obviously the wire is not grounding when you remove the "key"
 
Should shut off when you push the throttle all the way down. I've had my Tecumseh since 1995 and have never removed the plastic key, been in there since day one.

For the surging try some Star Tron.
 
I need to "dial in" the new carb- the old one was leaking so I just replaced it instead of trying to open it up, clean it and put it back together.
 
Should shut off when you push the throttle all the way down. I've had my Tecumseh since 1995 and have never removed the plastic key, been in there since day one.

For the surging try some Star Tron.
The surging is being caused by the spring on the throttle connection- the throttle is flapping around- I need to adjust things a bit. I have never owned a gas powered machine so I have 0 experience with small engines, Youtube is a great thing!
 
That is a good idea since those old Tecumseh carbs have rubber parts that degrade over time and likely aren't ethanol-resistant. The typical Briggs carb has little or no rubber and is more amenable to cleaning out and reusing.

Usually the only tuning adjustment on these carbs is the low speed mixture and the throttle plate stop screw. With the engine running with no load, hold the throttle plate lever on top of the carb against the stop screw. The engine should run slow and steady. If it dies out try holding it not quite to the stop as you adjust the mixture screw to try to get it to run better. After optimizing the mixture turn the stop screw so the "idle" speed held against the stop is considerably lower than normal operation, but it doesn't die out.

When you let go of the throttle plate and let the governor take over, it should rev up smoothly to governed speed and then not surge. If it stumbles during the rev up, turn the mixture screw a little richer (turn screw counterclockwise to open the fuel flow).

Surging occurs when the governed speed is exceeded so the governor pulls the throttle closed, but due to improper low speed adjustment the engine doesn't fire at all, so it slows down until the governor finally pulls the throttle wide open, then it fires up too fast and the cycle repeats.

Though some of these engines will just surge with no load no matter what you do. As long as it runs strong and steady in actual use it isn't a problem.
 
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Using an ohm meter, you should easily be able to determine if it is a bad switch or a ground issue.
 
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