Craftsman 10/28 Trac Blower, won't idle and eventually runs away, scary - Snowblower Forum : Snow Blower Forums
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post #1 of 68 Old 01-03-2016, 11:16 AM Thread Starter
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Craftsman 10/28 Trac Blower, won't idle and eventually runs away, scary

I got an old craftsman 10hp tecumseh snow blower. Owned it since "new" (sears "return")... 1987. It has never really run well going from constant surging when initially got to failing to idle well to not at all, to running away usually after taking off load (ie. at the end of a snow blow run)... scary.

I have tried various things during that period from cleaning the carb, ensuring floating is free movement, adjusting govenor arm, etc.

This year, in the fall, I started it up to make sure things were ok. It ran fairly well sitting in the garage and taking it for a "spin" around the driveway. Of course, temp was "nice" and no snow, so no load other than the track and free wheeling augers.

After trying to do the driveway with the first snow just after xmas (great that we made it that long!!!), it was in severe run out after each run down the lane... scary.

I tried everything to get rid of that issue, if I move the governor arm adjustment to reduce / prevent the "run away", then the thing basically stalls even with the trac movement. The small screw on the throttle control that is supposed control "top speed" appears to have little effect compared to the governor adjust changes. Overall, I still can't a proper idle mode regardless of where the governor adjustment sets. Moving the throttle control to the "idle position" usually causes the thing to die shortly there after (1-2 seconds). The idle mixture adjustment has no effect, totally closed or well open.... have cleaning / checked the "pinpoint" hole in the throttle body along with checking the needle.
If I adjust the idle speed throttle stop to help with idle, it has to be adjusted such that it seems to impact the normal operating speed to the point that causes a run away, just sitting there.
The choke position sets at 3/4 closed for cold start, and then usually is happy at half shortly there after and can be moved to about 1/4 or so once it is warmed although I usually keep in 1/2 ish mode to keep it running (hate having to do a manual pull if it dies away from electricity, its ok, but my shoulder has issues... that's why I have a snowblower).

When the thing goes to "run away", if I get a screw driver in at the throttle "tang", I can easily move the tang over to momentarily slow the engine down so the governor doesn't appear to be "stuck". As soon as I release the "tang", the throttle moves directly towards the idle speed stop screw (full throttle position) and heads for the "sky" again.

Not understanding exact how the governor works, but it appears that some how the governor "thinks" the engine is under load and it needs to "amp" up things... but I don't see what causes this. The spring around the shaft the throttle butterfly is relatively thin and weak so it certainly isn't forcing the issue to close the butterfly.

Not sure what else to say but help before I blow my machine or my self up... plus I am not sure how much more fume inhaling I can take... so hopefully some one will get me there sooner than later (or maybe winter will be nice and just go away... :-) ).

Thanks for any guidance as I am not sure what else to try.... although maybe my next door neighbor's new blower might be the answer... its darn quiet and runs like a lawnboy cutting grass.... just basically doing it job... :-)

Last edited by budwich; 01-04-2016 at 11:09 AM.
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post #2 of 68 Old 01-03-2016, 11:53 AM
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My bet is the plastic governor drive gear is broken. With it running at speed the arm should be trying to close the throttle, should be able to feel this by hand with the heat box removed.
Dont let this continue or you will be posting in the repower section.
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post #3 of 68 Old 01-03-2016, 11:59 AM
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Since you got this as a Sears "return" it implys something was wrong with it from the getgo, because somebody returned it. You might want to invest in a new carb which can be had pretty cheap on Ebay.

Have you reviewed some of the Youtube videos on how to set up the governor? This would be the first thing to try. There are a bunch, so find one that demonstrates setup on your engine. Donyboy73 has some excellent videos on all aspects of small engine care and repair.

By the sound of it, your internal governor mechanism MIGHT have come apart, which basically means that it's not working at all. It's also possible that in your adjustments, depending on how much you took apart, you might have some linkage in the wrong hole, a weak spring or a missing or wrong spring, a sticking throttle shaft, or a dirty carb with some passages blocked up. The fact that the mixture adjustment has no effect is a big hint.
Something might be binding, or something might be catching on an engine part if the springs and linkages are not in the exact right positions or a bit of sheet metal is bent and snagging something. Maybe post some pictures of the carb, governor lever and linkage and springs showing all the bits and somebody might see a problem right off the bat.

Basic governor operation.
The throttle butterfly is normally wide open with the engine off, and when it starts, the centrifugal weight gizmo inside the engine pushes a plunger that turns the governor shaft in the engine which is attached to the governor lever outside the engine which is attached by a linkage to the throttle on the carb. The moving governor lever closes the throttle to maintain the engine speed at about 3600 rpm max. The governor lever has a spring on it, which is tensioned to counter act the pressure of the governor shaft being rotated by the internal plunger inside the engine. If you have a throttle control lever, that lever basically reduces tension on the governor spring and lets the engine run slower. If the governor spring is too tight or has been stretched (which changes the tension) or hooked into the wrong anchor point (there are usually several holes to select from to get the tension right) then you could have all the problems you mentioned.

After rereading what I just wrote, I encourage you to check Youtube because video will show you what I am trying to say above.

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Last edited by Kiss4aFrog; 01-03-2016 at 03:22 PM.
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post #4 of 68 Old 01-03-2016, 12:02 PM Thread Starter
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Thanks. Although I have done alot in terms of auto / truck stuff, small engine is some what of a "unknown beast". Is the governor gear easy to get at (without having to disassemble the "whole engine" which I am pretty reluctant to do at this point in the winter? :-(

Having said that, your statement seems to indicate that the governor is / will be trying to close the butterfly which it is actually appears to be doing "constantly" once it get in the mode. In a "normal controlled mode", I do get some form of governor control / arm movement... but some how after load has been taking away, the governor some how stay "engaged" demanding more power when the arm should be moving out. To me, it almost looks like it is doing the oppose function / operation, after a period of time / post load.
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post #5 of 68 Old 01-03-2016, 12:10 PM
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Get yourself a tachometer. Tecumseh's will grenade if you excessively exceed 3600RPMs.

And review the governor adjustment procedures in the 4-stroke service manual found here. Link. (see page 26)


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post #6 of 68 Old 01-03-2016, 12:14 PM Thread Starter
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thanks... yes on the looking at the youtube stuff (yes Donyboy73 is excellent). That's what I have been following / using to give me some time away from the "fumes"... :-) I am not sure how much hydrocarbons my lungs can take... :-)

Related to your governor operation "note". Is the governor spring internal to the engine or visible from from the outside.
On this engine ("classic tecumseh"), there are two connecting wires (not springs in my view) at the governor arm, one goes to the throttle butterfly and the other goes to the throttle control lever. The throttle control level has a spring around its "components" that "link" the lever to a top speed adjustment screw which doesn't appear to do much. That particular spring has only "one loop". The other connector wire goes to the butterfly. the butterfly has a coiled spring around its shaft to force the butterfly close in "doing nothing" mode. Its tension is very thin but it does force the butterfly close when the carb is off the machine (on the bench) so it does work.

The connecting wires are in places as shown by the youtube videos.

The main air fuel mixture screw (bottom of the fuel bowl) works fine and readily adjusts things. Its the idle mixture screw that does not seem to do anything.

I guess the question is, what kind of effort is involved at getting at the governor?

I will try and get a picture or two... and then figure out how to post them herein

PS. I see picture "management" is straight forward like some other forums, so I just need to get the pictures.

Last edited by Kiss4aFrog; 01-03-2016 at 03:23 PM.
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post #7 of 68 Old 01-03-2016, 12:35 PM Thread Starter
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Quote:
Originally Posted by classiccat View Post
Get yourself a tachometer. Tecumseh's will grenade if you excessively exceed 3600RPMs.

And review the governor adjustment procedures in the 4-stroke service manual found here. Link. (see page 26)
that's what got me worried.

thanks for the link on the manuals, I haven't come across this particular one in my searches. I was using a soft cover "how to small engine" book ... the equivalent of "chilton".
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post #8 of 68 Old 01-03-2016, 12:51 PM Thread Starter
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Here is a couple of pictures of what the carb / throttle area looks like. One is a view from the throttle control lever side. The other, is from the governor side.

The spring on the throttle control lever area that goes to the top speed adjustment screw seems very sloppy and has only one turn around the "shaft" (not readily viewable from the picture). I don't actually understand what it is attempting to accomplish.
I added a couple of notes to the picture to help focus what I am taking about hopefully.
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Last edited by budwich; 01-03-2016 at 01:05 PM.
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post #9 of 68 Old 01-03-2016, 01:12 PM
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Quote:
Originally Posted by budwich View Post
...
The main air fuel mixture screw (bottom of the fuel bowl) works fine and readily adjusts things. Its the idle mixture screw that does not seem to do anything.

it sounds like you also have a restriction in the carb's idle circuit. Tecumseh carbs have tiny ports milled inside of the carb body that are infamous for getting clogged. The remedy is often a good soak in carb cleaner...&/or a trip through an ultrasonic cleaner.

when there isn't a load, but the engine is at the high-speed setting, the throttle should be barely opening therefore most of the idle & intermediate circuits are still supplying a substantial percentage of fuel.

The governor of course compensates by opening the throttle, like there's a load...however there isn't...hence the surging.


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post #10 of 68 Old 01-03-2016, 01:13 PM
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There should be a governor spring external on the engine, hooked to the governor lever on one end and the throttle lever on the other end. I didn't see one on your photos. That might be your problem. The spring acts in opposition to the internal device to find a balance between the engine pushing on the external lever in one direction, and the spring pulling to opposite way.

The spring over the speed adjustment screw is there to provide tension on the screw so it stays put when you adjust it and doesn't vibrate and unscrew itself. The screw should be in far enough that the spring is compressed somewhat so it does hold the screw snug in the threads.

The internal part of the governor requires that you remove the engine case for access so its not a 5 minute fix.

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Last edited by Kiss4aFrog; 01-03-2016 at 03:23 PM.
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