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Discussion Starter #1
I have a tecumseh hmsk80. Starts fine, runs great under most loads. This model TEC has a spring on the throttle lever that runs to the governor (just FYI). If I give it a chore (a little deeper snow, 12in instead of 6in, etc) it will do one of the following:

  1. A sort of stall/surge dance wherein it kinda surges as it slows to a stall and dies.
  2. Or, if I back off the load, here is the interesting part: it surges and surges and will not stop until I lower the throttle half way, then raise it back up - good to go again.
I suspect governor settings (or linkage?), but not sure how to fix. Some reading suggests it could be the carb main jet, but I've already cleaned it (might not be adjusted right I suppose, this is the one where the screw is at the based under the bowl).

Thoughts? Anyone have this happen to them?
 

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:welcome: to the forum Roachslayer


Was this the problem you had to start with that you removed the carb for cleaning to solve or is this new since cleaning the carb ??

Even though you've tried to clean it there might still be something you missed in the carb and it's still a bit gummed up.
It sounds like it's not getting enough fuel which can be from a restriction at the out of the fuel tank or the fuel line deteriorating so badly inside it's choking off flow or a bad fuel shut off that's not opening all the way or restricted/clogged fuel filter. I'd pull the line at the carb and make sure it's flowing out of there nice and strong.

If you have good flow then it's likely something still causing a restriction in the carb. You're sure you reconnected the linkages correctly ??

You can get a whole new carb for about 12 bucks shipped from Ebay if you have the one I think you do. Just ordered one for my Snapper 10HP. It's just to cheap new to mess with cleaning. (Will hang on to the old one).

Please post your full engine ID numbers.

Genuine Tecumseh 632370 Carburetor
 

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stalling motor

I had issues with surging motors before....I usually google donyboy73 on youtube.


usually find a video fixing your small engine problem :)

Can always gear down and blow snow slower if you're stalling.
 

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Just two cents from another dummy: My recent experience with 2-strokes with surging is that the air/fuel mixture is too lean. (For instance if you buy a jet ski in Reno and try to run it on the river at 23', it will surge. Way to test, is to see if it surges with choke on a little. If it stops the surging, adjust the idle and high speed jet (screw out) to stop the surging.

There are true gurus here which hopefully can refine or contradict with my analysis.
 

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For this, I suspect your fuel mixture may be off a bit. If you have a jet adjustment screw on the bottom of your carb bowl, try turning it slowly in one direction to see if it clears up the surge. If not, try it in the other direction.
 

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Given the fact that it runs and blows 6-8 inches snow at medium forward speed like butter, I'd say it is not a fuel issue (not ruling it out, just evaluating probability). It only stalls when hitting the older snow (more compact). I would expect an engine to stall and die if I truly hit unmovable snow and halted drive train, but not this odd surging thing, right?

I took the carb apart just out of personal policy when buying a used machine - open it up, clean it out. But it was pristine in there. Cleaned it and blew compressed air anyway for good measure.

I suspected governor as soon as I saw the fact that it would surge and more specifically recover after brining it down to half throttle, then back to full. BTW, I cannot floor it... I have to bring it slowly up to full speed or it stalls. I have see the above video and others, tinkered with it, still not quite sure why I haven't been able to resolve it yet.
 

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The governor is trying to accomplish what it's designed to do, keeping a constant engine speed under load. As the load is increased on the engine, the governor opens the throttle, seeking additional fuel. If that fuel is not available, the engine falters, as indicated by stumbling/surging, and or stalling.

Tecumseh carburetors are finicky, and need to be pristine inside, in order to deliver optimal performance, or in some cases, even run. As suggested above, make certain that the fuel line is clear, and that there's no debris trapped on the upstream side of the float needle seat. During a normal carb cleaning, I remove the seat, and blow compressed air through the fuel inlet with a rubber tipped blow gun.

With both the main, and pilot jets removed, clean these with some Gumout, then run a piece of wire through all of the tiny holes. The pilot jet is on the side, and on newer models, resides under a black rubber cap, easily removed with a scratch awl.

Donnyboy is awesome, and I think he has a video up on Youtube of this.
 

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Discussion Starter #12 (Edited)
a quick update, here is what I did:

  1. I added a tac so I could see the RPMs. It was running at 3200 at the top end. I set it to 3400 using the governor screw (knowing 3600 is max, but this thing is old, should I push it?).
  2. I found the idle mixture screw was almost all the way in. So I set it at 1 1/4 turns out (thanks Donnyboy).
  3. I adjusted the main screw just a bit above too lean to stall, but not much, it was already close to 1 1/2 turns out. (again, thanks Donnyboy).
I then took it out and tried pretty hard to stall it and couldn't. I wonder if it was the governor?? Surely the idle mixture won't affect top end performance (but it did fix my idle issue I happened to have). And my tweak to the main jet was super minor. (also, I did already have it all apart, totally clean out, compressed air).
 

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a quick update, here is what I did:

  1. I added a tac so I could see the RPMs. It was running at 3200 at the top end. I set it to 3400 using the governor screw (knowing 3600 is max, but this thing is old, should I push it?).
  2. I found the idle mixture screw was almost all the way in. So I set it at 1 1/4 turns out (thanks Donnyboy).
  3. I adjusted the main screw just a bit above too lean to stall, but not much, it was already close to 1 1/2 turns out. (again, thanks Donnyboy).
I then took it out and tried pretty hard to stall it and couldn't. I wonder if it was the governor?? Surely the idle mixture won't affect top end performance (but it did fix my idle issue I happened to have). And my tweak to the main jet was super minor. (also, I did already have it all apart, totally clean out, compressed air).
Roach,
Would you give additional details about the tac you installed? What...where etc...been wanting to do this for awhile and dont know how/where to start! TIA
 

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Discussion Starter #15
@Opfoto, do a search on Amazon for "Docooler Digital Engine Tach". It's a cheapy, but it seems to work.

There are several providers of this same tach under different names. I am sure they all come from the same plant in China. But there are also a couple different models. Make sure you don't just get an hour meter. Get the hour meter + tachometer.

To install just wrap the wire end around your spark plug wire (right on top of the engine for most of our snowblower cases). Give it at least 3, maybe 4-5 turns around your plug wire, making a nice tight coil. Tape or zip tie it. Cut off extra, and consider a dab of silicon or glue or something to keep the moisture out of the end of that cut wire. And actually... you should decide where you want to tach positioned and then run the wire down to your plug before doing this wrap.

What threw me were the instructions. It has to be set up for 2 stroke vs 4 stroke, vs V-twin (it's just sensing for spark intervals, but doesn't know how many strokes to apply in its calculation). It's easy to set, but wasn't clear on which option (they give you like 4 choices). I set mine on mode "2" which seemed to produce the expected RPMs for these single cyl 4 stroke engines. But what threw me is that mode 2 was labeled as the spark firing "once per revolution" which I expected to be the 2 stroke. But there is no way the other settings are correct (RPMs were off by a factor of 2). Hope that makes sense, and saves you some trouble.
 

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What threw me were the instructions. It has to be set up for 2 stroke vs 4 stroke, vs V-twin (it's just sensing for spark intervals, but doesn't know how many strokes to apply in its calculation). It's easy to set, but wasn't clear on which option (they give you like 4 choices). I set mine on mode "2" which seemed to produce the expected RPMs for these single cyl 4 stroke engines. But what threw me is that mode 2 was labeled as the spark firing "once per revolution" which I expected to be the 2 stroke. But there is no way the other settings are correct (RPMs were off by a factor of 2). Hope that makes sense, and saves you some trouble.
It's called a wasted spark. The magnets go by and you get a spark. it cant help it. You get a spark with every rotation whether you need it or not.
 

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I have a tecumseh hmsk80. Starts fine, runs great under most loads. This model TEC has a spring on the throttle lever that runs to the governor (just FYI). If I give it a chore (a little deeper snow, 12in instead of 6in, etc) it will do one of the following:

  1. A sort of stall/surge dance wherein it kinda surges as it slows to a stall and dies.
  2. Or, if I back off the load, here is the interesting part: it surges and surges and will not stop until I lower the throttle half way, then raise it back up - good to go again.
I suspect governor settings (or linkage?), but not sure how to fix. Some reading suggests it could be the carb main jet, but I've already cleaned it (might not be adjusted right I suppose, this is the one where the screw is at the based under the bowl).

Thoughts? Anyone have this happen to them?
HOPE THIS HELPS

Tecumseh Carburetors

All models with float-type carburetors
Main Pre-set 1-1/2 turn
Idle pre-set 1 turn


NOTE: OVERTIGHTENING WILL DAMAGE THE TAPER PORTION OF THE NEEDLE. All adjustments should be made with the carburetor in the operating position.
Turn both the main and idle mixture adjusting screws in (clockwise) until finger tight. Now back the mixture screws out (counterclockwise) to obtain the pre-set figure in the charts shown above.


FINAL ADJUSTMENTS (NON EMISSION ENGINES)

Start the engine and allow it to warm up to normal operating temperature (3 - 5 minutes). Set the speed control to the HIGH or FAST position. From the recommended preset position, turn the main mixture adjustment screw in (clockwise) slowly until the engine begins to run erratic (lean). Note the position of the screw. Now, turn the screw out (counterclockwise) until the engine begins to run erratic (rich). Turn the screw in (clockwise) midway between these two positions. This will be the best setting.
Set the speed control to the IDLE or SLOW position. Adjust the idle mixture screw following the same procedure used to adjust the main mixture adjustment screw.


POSSIBLY YOUR PROBLEM

First make certain the governor is set properly. It should not be set to the major or minor.

Double check linkage...donyboy73 has a vid on youtube as to which holes rods should be placed but keep in mind that it is not definitive so you might want to look with a magnifier to see which hole is shiny from wear (that is how I determined)

If further adjustment is required, the main adjustment should be made under a loaded condition.
If the engine stops or hesitates while engaging the load (lean), turn the main mixture adjusting screw out (counterclockwise) 1/8 turn at a time, testing each setting with the equipment under load, until this condition is corrected.
If the engine smokes excessively (rich), turn the main adjusting screw in (clockwise) 1/8 turn at a time, testing each setting with the equipment under load, until this condition is corrected.
After the main mixture screw is set, move the speed control to the IDLE or SLOW position. If the engine does not idle smoothly, turn the idle mixture screw 1/8 turn either in (clockwise) or out (counterclockwise) until engine idles smoothly.
Recheck the high and low R.P.M. setting and adjust as necessary.
 

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there is a tiny passage inside the carb, in the round main jet channel, it has to be cleaned from inside the center with an angled torch tip cleaner or pin. theses get blocked and will give you all kinds of headaches, they usually go undiagnosed cuz the passage can't be seen from the outside easily when the carb bowl and float are removed. but this problem will DRIVE YOU NUTS. if you can get a known good carb and swap it on, if it fixes it, that passage is the problem.

today's gas is junk, due to the 10% alcohol content, and it creates a lot of hard powder like buildup inside the carburetor and fuel system, worse than the old non-alcohol or leaded gas ever did. these fuel companies should be sued for the low quality of the fuel they are selling us, it does a number on small engines and power equipment.

only use premium in small engines, it's not quite as bad as the regular.
 

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It's very low resolution, but you can kind of see the wasted spark in this animated gif.
edit; easier to see in the video vs the gif
https://www.youtube.com/watch?v=sjAKdpltV4o&feature=share

the new cars use that system to also reduce HC emissions
if you notice when the plug fires at tdc exhaust, there is some slight
cumbustion around the intake valve anyway
that cuts down on emissions out the tailpipe esp. in a bigger V8 V6 engine.
less unburned fuel goes into the converter as well, adding to converter life.
 
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