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Discussion Starter #1
Craftsman 22" with Tecumseh 12 cu in engine, series 1 carb.

My brother and I both have identical Craftsman snow blowers with the same problem. They start and run but when engaged to throw snow they die.

Mine is about 15 yrs old with a new carburetor (eBay), adjustable main and idle jets. I've owned it since new and it's only been the last few years that it has given me trouble. His is newer with the non adjustable carb.

We've been through the cleaning procedures and both carbs are spotless. We're at the end of the rope here, with major snow headed this way.

What is the likely culprit?

TIA
 

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some one will be along here to answer that question. I never run or mess around with those engines. so anyways ALOHA from the unfrozen TUNDRA.:eek::eek::eek::eek::eek::eek::eek::eek::eek::eek::eek:
 

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older L head techumseh engines have a bad habit of the exhaust valve recessing in the valve seat and loosing valve lash. When the engine gets up to operation temperature the valve lengthens just enough to hold the exhaust valve open causing a loss of power. This among many other things could be an issue.

Make sure the gas tank is vented, you have good spark, and you already said the fuel system is working correctly. make sure you have good fuel delivery to the carb.
 

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Yes. Exhaust valves tend to get out of adjustment as well as the carburetor s are really finicky. To fix Exhaust remove head and using a wire brush remove carbon from valves. Pull the door to the valve spring area and using a valve keeper removal tool pull valve keeper clip and the pull valve out. To fix you usually grind off a small amount of stem until clearance is correct when measured from the cam lob tappet to the valve stem. Also you need to lap the valve too to make sure it is seated correctly. If valve is damaged replace valve and grind to right length and lap to cylinder.
 

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Or maybe your machines are just running lean.....try running it with the choke on just a bit.....if this helps.....open your main needle valve just a bit, very small bits at a time.

His is newer with the non adjustable carb, more likely to gum up....may need to be cleaned by soaking in carb cleaner.
Good luck
 

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Something else to check.
Mine was sucking in air through the plastic fitting the goes into the carb. Did they same thing, as soon as I went into the snow it died.
Funny thing was that the fitting didn't leak gas until I finally wiggled it around, then I saw the crack.
Do you have the plastic fitting on yours?

Check the condition of the fuel line itself too.
Bad venting on the cap as mentioned.
 

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When you say this, "They start and run but when engaged to throw snow they die."

Does it die, just when you engage the auger?
Or when you engage the auger and go into the snow, then it dies?
 

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the load!!!
I'm fairly certain the OP is looking for a culprit within the spectrum of his snowblower.

Try pulling the plug and checking to see what the fuel mixture is doing in the chamber.
 

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I follow what BigEd is getting at, and is what I was wondering...Does it run OK auger engaged without any snow ?? Assume that's what you meant by load...? Otherwise it could be a faulty safety switch, and it is shutting off the ignition..
 

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Discussion Starter #12
Thanks for the replies, guys.

are you able to test compression?
I have a compression tester, and the machine has electric start, so yes I could. Never seen a spec for that though. Any idea what it should read?

Something else to check.
Mine was sucking in air through the plastic fitting the goes into the carb. Did they same thing, as soon as I went into the snow it died.
Funny thing was that the fitting didn't leak gas until I finally wiggled it around, then I saw the crack.
Do you have the plastic fitting on yours?

Check the condition of the fuel line itself too.
Bad venting on the cap as mentioned.
Yes, they all have plastic fuel inlet fittings. No drips though. I'll double check the gas cap vent.

Fuel line has been replaced. I installed a shutoff valve this year in the fuel line, and I've double checked that fuel flows through it OK. Spark plug is new.

When you say this, "They start and run but when engaged to throw snow they die."

Does it die, just when you engage the auger?
Or when you engage the auger and go into the snow, then it dies?
By stalls under load I mean when I push the machine into some snow. I can drive the thing around and engage the auger but as soon as it gets into even a couple inches of snow it wants to stall.
 

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It sounds like your auger belt is slipping. Are they both the originals from 15 years ago?

I'll guess that when you pull the auger handle, the auger and impeller spin like they are supposed to but when you drive into the snow it will throw the snow okay at first and slowly throw the snow shorter and shorter until it just stops coming out of the chute and the engine stalls? While this is going on, you never hear the governor kick in and up the rpms? Classic belt slipping symptoms.
 

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Discussion Starter #15
It sounds like your auger belt is slipping. Are they both the originals from 15 years ago?

I'll guess that when you pull the auger handle, the auger and impeller spin like they are supposed to but when you drive into the snow it will throw the snow okay at first and slowly throw the snow shorter and shorter until it just stops coming out of the chute and the engine stalls? While this is going on, you never hear the governor kick in and up the rpms? Classic belt slipping symptoms.
A couple of things about what you've said ring true. The auger belt has been replaced recently, and the replacement was fairly easy to install. Maybe it's too long? Unfortunately I can't see the auger while operating the machine.

But why would the engine die instead of the governor kicking up the speed?
 

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A couple of things about what you've said ring true. The auger belt has been replaced recently, and the replacement was fairly easy to install. Maybe it's too long? Unfortunately I can't see the auger while operating the machine.

But why would the engine die instead of the governor kicking up the speed?
Another thing to check are the RPMs that you're running. do you have access to a tachometer?
 

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you won't know if the governor is failing unless you're looking at the throttle plate while it's stalling.

If the engine is @/near WOT and the RPMS are still dropping like a rock, the governor/linkage is doing it's job...it's trying to deliver more fuel as the spool retracts.

What are the RPMs before the load is applied?...if they're too-low (3600RPM is max) then adjust to give your machine a fighting chance.

As mentioned earlier, you want to check compression. Gustoguy and CarlB mentioned the valve issue...bad valve seats and/or valve lash lead to low compression. There's not really a spec that I'm aware of mainly due to the compression release mechanism....as well as variation in testing. I'd say questionable compression when pull starting is anything below 50 psi...below 40 I'd say you definitely have a problem. On my HM80, with a new head gasket and valves lapped, I'm getting 135psi on the starter cold. My H35 that I also put a new head gasket and lapped the valves, I'm pulling around 80psi cold. Others recommend leak-down testing...I've never done this on an l-head.

Anyways, you're getting a lot of good suggestions thrown your way. One more is to find the L-head service manual and browse the troubleshooting guide. I'll see if I can find the link on here for ya! Good luck!

EDIT: Link for the service manual.
 

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It sounds Iike it could be a carburetor problem. Try adding a small amount of choke to the engine and if that prevents stalling the clean then clean the main jet and emulsion tube. You may want to try an aftermarket replacement carburetor too to see if that fixes the problem. Then again it could be due to exhaust valve not closing fully and this can really reduce power.
 
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