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Hot!4 hp Tecumseh HS40 - new carb, Runs full throttle, can't set idle

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LakeWobegonMN
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2020/10/27 16:31:42 (permalink)
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4 hp Tecumseh HS40 - new carb, Runs full throttle, can't set idle

Hi folks,
 
I'm trying to get a Tecumseh HS40 engine running well on an old Toro 421 Snowblower.
 
I replaced the carburetor, put new fuel lines, new spark plug, and am running canned TruFuel ethanol free gas.
 
The motor started right up, it was choked fully.  I quickly reduced and then eliminated the choke, and it still ran just fine. (Yipee!)
 
Then, I lowered the throttle lever to idle, and the rpms barely dropped.
 
I started to adjust the idle speed screw (not the idle mixture screw), and the idle started to lower a bit, but then would sputter out.
 
So, runs great at full throttle, no choke required.  I can only adjust the idle down to what sounds like 3/4 of full throttle...any lower, she sputters and stalls out.
 
This carb has 3 adjustments: (1) Power, at the bottom of the bowl, (2) idle mixture, and (3) idle speed.
 
Because of the angle of the fuel inlet on the carb, I did have to bend/kink the fuel line a bit.  But it's getting plenty of fuel in the bowl, as it will run full throttle all day.
 
Does the above sound like something pretty simple I need to adjust?  I am new to this.
 
I've ordered a cheap tachometer to use as a sanity check to see what I'm dealing with.  But, it's very clear that the idle is way too high.  I know a snow blower is operated at full throttle when blowing snow, so this maybe isn't a huge deal - but I'd like to get it running right.  The manual says the top end unloaded RPM should be around 3400, and the idle should be around 1700.
 
Thanks for any advice!
 
 
post edited by LakeWobegonMN - 2020/10/27 16:37:35

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    dillonm695
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    Re: 4 hp Tecumseh HS40 - new carb, Runs full throttle, can't set idle 2021/02/01 18:08:41 (permalink)
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    Welcome to the world of carburetor adjustment!  I'd say your new carb is not set up right and you'll need to figure that out.  Try searching online for instructions for that particular carb.  I've rebuilt a couple of 2-stroke carburetors and just one 4-stroke, and one thing for sure is you need to have the proper documentation to get it right.  If you don't have the right instructions for YOUR carburetor, you may need to get help from a pro.
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