# Tecumseh HMSK 100 will not idle



## Dave9354 (Dec 11, 2010)

I have a Tecumseh hmsk 100 on my noma snowblower. It runs only at high speed no matter where I move the throttle. It will not run at slow speed. Was wondering what is causing this? All the linkages seem to be in correct position. Any help would be greatly appreciated. Thanks, Dave.


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## ELaw (Feb 4, 2015)

I'm a little unclear on the question: are you saying it runs fast regardless of whether it's set to fast or slow, or that it dies or runs poorly at low speed?

If it runs fast all the time, something in the throttle linkage may be stuck - can you post a photo of the linkage (there are quite a few different ones)?

If the engine "tries" to slow down but won't stay running or has other problems at low speed, it's most likely the carburetor.


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## Pythons37 (Nov 9, 2012)

Buy a carb on ebay/Amazon. About 25-30 bucks.


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## Dave9354 (Dec 11, 2010)

It stays running at high speed if I move the throttle to high or low speed. It does not stop running at all. All the linkage to throttle and governor are all moving. Nothing is stuck. Never touched any linkages since I bought machine brand new about 15 years ago. I will see if I can post a picture of linkage.


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## ELaw (Feb 4, 2015)

If the actual throttle plate on the carb is moving and the engine speed is not varying, pretty much the only possibility is that the throttle plate inside the carb has come off. That's pretty rare but it does happen.

You should be able to check by (with the engine not running) opening the choke fully, and looking inside the carburetor while moving the throttle plate by hand. You should see the throttle plate opening and closing the passage at the far end of the carb. If all you see is a rotating shaft with a slot and two holes in it, your throttle plate has gone AWOL.

Best bet in that case would be to replace the complete carb, but you also have to figure out where the throttle plate went. If you're lucky it's stuck in the intake manifold or port. If you're less lucky it is inside the cylinder or head or went through the engine.


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## Kiss4aFrog (Nov 3, 2013)

I think if the throttle plate came off and it went full throttle it would have thrown the connecting rod right through the starter.

I'd still check it out with a flashlight to see if you can see a plate and if it's moving.

Pictures of the linkage will be helpful when you have a chance.


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## ELaw (Feb 4, 2015)

Good point!

Although I can say from personal experience (when I was young and stupid and fooling with engines that cost me around $0) that it is definitely possible to run a Tecumseh (or Briggs) engine at wide open throttle for minutes at a time without ventilating the block.

It's also possible (although even less likely than the throttle plate coming off in the first place) that the plate lodged somewhere where it restricts flow.

Another possibility is that the idle-speed screw is cranked in so far that "idle" is the same as "fast". That's pretty unlikely to happen unintentionally though.


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## Dave9354 (Dec 11, 2010)

Throttle plate is intact.


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## Pathfinder13 (Feb 28, 2014)

On YouTube, Doneyboy73 has a video on how to fix this condition, the cause and remedy, for Tecumseh engines that develope this. It may or may not be this problem, but this is worth a look.


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## Dave9354 (Dec 11, 2010)

Thanks for the video pathfinder13. My throttle plate is a little loose, not as much as the video. I will try the fix tomorrow and let you know if that was the problem.


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## classiccat (Mar 1, 2014)

is there any crud / corrosion on the carbs throttle shaft spring?

I had one that wouldnt snap back to idle when the governor spring tension was removed (low speed throttle setting). A little mmo on that throttle shaft spring cleared-up the issue.


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## Pathfinder13 (Feb 28, 2014)

One thing.. if you remove any linkages either make a little diagram or snap a picture first, as it's easy to forget which one goes in which hole.


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## Dave9354 (Dec 11, 2010)

Problem solved! I repaired the throttle plate shaft according to Pathfinder 13 's video that he posted and it is idling perfectly! Thanks to all that posted your suggestions as they where all valuable tools in diagnosing the problem.


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## Kiss4aFrog (Nov 3, 2013)

Nice to DIY and save a trip to the shop and the bill


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## Pathfinder13 (Feb 28, 2014)

One night I was bored so I watched some of Doneyboy73 's older vids... that's the only reason I was able to assist. You know how it is, nothing on TV, might as well grab the laptop ..hehe.  Glad you were able to repair it !


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