4cycle snowblower tuning gurus?

[frascati]

My SB has a Tecumseh oh318ea 11hp motor. It runs like a champ. However. If I need to make a long pass through extra heavy snow after about a minute it starts to balk and stutter and lose power and rpm. I need to stop and let it complain for another full minute, with no load, for it to recover.

So when it's under load the governor linkage opens the butterfly to try to maintain consistent rpm. It does this wonderfully by the way, since it's a 1978 toro 24in that had a 7hp Lhead that I replaced with an 11hp ohc. So it maintains rpm. But soon starts to stumble and want to quit.

So is it too rich? The carb does have a needle adjustment screw under the bowl. And I also wonder if the governor linkage adjustment could be causing this But I'm hoping to get some advice on what is going on here before I go hunting with adjustments.

 

[Firebrick43]

Probably need the carb cleaned and overhauled. It can also be an ignition coil problem. Many times the coils have an internal break that maintains continuity when cold but as the motor heats the coil up and it expands the break opens. Have you removed the tin work and checked for plugged fins/mice nest?

 

[PoorUB]

I bet if you take the float bowl off you will see the problem! chances are the carb is plugged up from old gas.

Rich is usually not a problem, lean is a big deal. Does it have and adjustable high speed jet in the bottom of the carburetor? turn it out until the engine stumbles a bit, then turn it in until it clears out and run it there.

If it has a fixed jet in the bottom of the carb, take it out and make sure it is clean. Clean the float bowl too. Then screw it back together at try it out.

 

[The Cobbler]

fuel/ carb issues are the most common problems with small engines .
probably a good carb clean will help your problem

 

[theoldwizard1]

My SB has a Tecumseh oh318ea 11hp motor. It runs like a champ. However. If I need to make a long pass through extra heavy snow after about a minute it starts to balk and stutter and lose power and rpm.

If it is mis-firing, I would think that the magneto is weak (incorrect gap?) or the points need to be filed.

After that, I would guess it is too lean. Does it recover quickly when you add choke ?

 

[theoldwizard1]

fuel/ carb issues are the most common problems with small engines .
probably a good carb clean will help your problem

I am not disagreeing, but ...

Lean condition usually result in engine speed reving up and down as the governor tries to compensate.

The most common carb problem with small engines oscillating is a clogged primary (low speed) jet. The carb needs to be removed, disassembled and all passage reamed with a fine wire.

 

[finn]

Most likely, in my opinion, is that the carburetor is icing, and when you reduce load there isn’t as much air velocity so there’s less evaporative cooling and the ice quickly melts. I used to run into that on snowmobiles when I was a kid back in the sixties (when snowmobiles had 8-10 hp engines).

Tecumseh called the old snowblower engines Snow Kings, and I remember them being calibrated for cold weather use. I thought they had some sort of carb heating ducting, but I might be wrong about that.

 

[The Cobbler]

snow king engines had a shield around the carb that trapped some heat from the exhaust . I think they also have a dropped intake manifold to reduce chances of flooding on start up

 

[frascati]

Wow. You guys are GREAT. I posted this at the same time at two other forums and got no response at all.

I don't think its icing since load does not decrease rpm/airflow. But the governor is giving it more fuel when it senses a lowering of rpm at the same throttle setting. That's why I thought too rich.

Before I start messing with settings I'll remove the bowl and do some cleaning.

 

[finn]

snow king engines had a shield around the carb that trapped some heat from the exhaust . I think they also have a dropped intake manifold to reduce chances of flooding on start up

That’s what I remember now. I recalled that it wasn’t very elaborate, but I never had icing issues with them.

 

[Jlbc212]

Years ago I had an old snowblower with an 8hp Tecumseh engine. The carburetor adjustment screw for the main jet would turn itself from the engine vibration. A new spring may have fixed the problem, but it was easy enough just to reach down and readjust the screw.

 

[rmanrman]

Years ago I had an old snowblower with an 8hp Tecumseh engine. The carburetor adjustment screw for the main jet would turn itself from the engine vibration. A new spring may have fixed the problem, but it was easy enough just to reach down and readjust the screw.

If the carb was running rich you would see black smoke out the exhaust
I’ve had a hot restarting problem turned out the magnito was failing
Do you run out the gas at the end of the winter season?
Do you use a Gas stabilizer like “Stabil when you fill up the gas can?
I’ve been doing this for every small gas engine for about 20 Years never had a problem with the carbs even in my 60 hp boat engine
Stabil is expensive but not as a new carburetor or time for service.

 

[Mick56]

Is there a fuel filter somewhere? Could be partially plugged. Or the vent in the cap could be plugged.

 

[theoldwizard1]

snow king engines had a shield around the carb that trapped some heat from the exhaust . I think they also have a dropped intake manifold to reduce chances of flooding on start up

They also mount the fuel tank on the opposite side of the engine from the carburetor and run the fuel line behind the rewind cover so that the fuel picks up some heat from the engine.

 

[PoorUB]

I am not disagreeing, but ...

Lean condition usually result in engine speed reving up and down as the governor tries to compensate.

The most common carb problem with small engines oscillating is a clogged primary (low speed) jet. The carb needs to be removed, disassembled and all passage reamed with a fine wire.

If I need to make a long pass through extra heavy snow after about a minute it starts to balk and stutter and lose power and rpm.

This is not a low speed mixture issue.

A long pass through heavy snow it is running on the high speed mixture only.

 

[PoorUB]

They also mount the fuel tank on the opposite side of the engine from the carburetor and run the fuel line behind the rewind cover so that the fuel picks up some heat from the engine.

Tecumseh just builds them that way, nothing to do with heating the gas line! Tecumseh engines that run in the summer are built the same way, You certainly don't want to heat the gas line in the summer.

 

[The Cobbler]

They also mount the fuel tank on the opposite side of the engine from the carburetor and run the fuel line behind the rewind cover so that the fuel picks up some heat from the engine.

I think that would be blowing cold air on the line from the flywheel fan , not heated air

 

[Noltz]

They also mount the fuel tank on the opposite side of the engine from the carburetor and run the fuel line behind the rewind cover so that the fuel picks up some heat from the engine.

Now I had an issue with a 10hp Tecumseh with this setup and the hose was restricted. Idle and operating speed were fine but if I dug into heavy snow the bowl would run dry. It wasn't OEM hose but something thicker. So I think you might be right about a restriction in a jet or even dirt in the float needle.

Wow. You guys are GREAT. I posted this at the same time at two other forums and got no response at all.

I don't think its icing since load does not decrease rpm/airflow. But the governor is giving it more fuel when it senses a lowering of rpm at the same throttle setting. That's why I thought too rich.

Before I start messing with settings I'll remove the bowl and do some cleaning.

When you pull the bowl keep it upright and look in the bottom for water. Water will glob together and can stop gasoline from getting drawn up main jet.

 

[RichWolfson]

Clean the carb and try new fresh low-test gas. If you can, get gas with no alcohol.

 

[DGersic]

My SB has a Tecumseh oh318ea 11hp motor. It runs like a champ. However. If I need to make a long pass through extra heavy snow after about a minute it starts to balk and stutter and lose power and rpm. I need to stop and let it complain for another full minute, with no load, for it to recover.

So when it's under load the governor linkage opens the butterfly to try to maintain consistent rpm. It does this wonderfully by the way, since it's a 1978 toro 24in that had a 7hp Lhead that I replaced with an 11hp ohc. So it maintains rpm. But soon starts to stumble and want to quit.

So is it too rich? The carb does have a needle adjustment screw under the bowl. And I also wonder if the governor linkage adjustment could be causing this But I'm hoping to get some advice on what is going on here before I go hunting with adjustments.

I’m going to go a different direction here. Everybody jumps on the carb and gas first. If it starts and runs ok, and generally seems to be working, I’m going to suggest that the carb is fine.

A full minute of heavy load and it starts to lose RPM, then takes a minute or so to recover, I’m wondering if it’s starting to overheat.

I had a lawnmower with a Tecumseh engine that would run great right up until it would overheat and die. So what you’re describing sounds kinda familiar.

Is this engine a Snow King? Or are we assuming that because it’s a Tecumseh and it’s now on a snow blower? What was it mounted on originally?

 

[Motown]

Those big Tecumseh have a habit of hammering the valve seat down in the block, also. And they will start to pop out the exhaust. Something to keep in mind.

 

[finn]

The other zero cost thing to try is throwing a little choke at i when it starts to stumble. If it clears up, rebuild the carb. It’s partially clogged or the fuel pump diaphram has hardened.

 

[nbpt100]

When ever there is a small engine problem, regardless of the board, 90% of the answers are some form of clean the carb.

It is true it s a very common problem. It makes me laugh. It may very well be, However, Far from the only possibility. It does sound like a fuel delivery issue. It would be good to have more info.

Everyone is assuming it is a Snow King engine. It Probably is as it was the #1 snow blower engine on US built machines for decades. but please confirm. You did say you re powered it. Exactly what is on it now? Can you take a pic. I would love to see how you fit that 11HP on that 24" Toro. Does it have points and condenser or electronic ignician? Did you pull the plug and see if it is running lean or rich? I only use Champion or NGK in Tecumseh engines. Do not use those E3 or other cheap plugs.

If you have a warm weather engine on it, and did not make a heat box, you do have to worry about icing. Also, you need to be concerned with the governor link getting interfered with by ice forming and snow landing on it. When you get into deep snow is the snow falling over the top of the bucket and hitting the Governor link????? Is that maybe the problem? Just thinking out side the current box here.

If you decide to clean the carb (which is very reasonable) take it off and do a thourogh job by removing both jets. Dont just do a half *** job. Even if the bowl looks very clean. Check the float for proper height. Also check for good fuel flow from the fuel line. There is a screen in the bottom of the tank. Make sure it is not partially blocked or the hose has a restriction. Does it have a gas shut off? make sure it is not acting as a restriction and is fully open. The gas tanks come off pretty easily.

Also check the valve lash. Easy to do when the carb and muffler are off. This is also common on these engine at Motown already said. The exhaust valve may not be fully closing as it may show up when you need power and the engine gets hotter.. If you run with the valve lash too low, you can ruin the engine. Or at least need an expensive valve job which for most practical purposes totals the engine.

I would suggest you check the valve lash with feeler gauge, in any event, if you have not already. If you run at night and see a Red Glow of the muffler that is good clue the valve is not seating 100%. It could mean other things too. But a simple to observe clue you could have this problem.

I hope this gets you thinking beyond the standard responses and you can solve the root cause.

Let us know how you are making out and post a few pics if you can. Good Luck!!!!

 

[PoorUB]

Does it have points and condenser or electronic ignition?

It is an OH318EA, they were all electronic ignition, so I doubt it is ignition related, although a new spark plug would not hurt.

Good question if it is a snow king as the air shroud over the carb does make a difference.

I ran a small engine shop for a few years. Snowblowers? Like you say, 90% of running issues is carb related. Most don't get enough hours on them to have valve issues, and the newer engines have electronic ignition which getnerally works or it desn't.

 

[Bert_]

I don't think its icing since load does not decrease rpm/airflow. But the governor is giving it more fuel when it senses a lowering of rpm at the same throttle setting. That's why I thought too rich.

When you evaporate fuel you lower the temperature. High load = lots of fuel. Large temperature drop.

I vote either restricted fuel supply or carb icing.

 

[joel_400]

Another of the Tecumseh fuel tanks had a screen in the bottom at the ****** for the hose to attach...seen more than one plug up over the years. Pull the tank, punch it out, and add an inline rock catcher fuel filter. And while your at it replace the fuel hose to the carb to make sure there aren't rubber pieces floating around and turning sideways causing intermittent fuel blockage. If it runs good for a pass then starts acting up maybe it's because the carb bowl is just about out of fuel by the end of the run and letting it "catch" up temporarily fixes it until the "supply" problem kicks back in....kinda reminds me of our economy right now...."supply chain issues" haha
Joel

 

[frascati]

And it was....

Restricted fuel supply.

Once again, you guys ROCK. I think you're right. I'll look to see if there's a screen in there. I'm ashamed to admit that after all I forgot a cardinal rule to keep it simple. Occam's razor and all that. Finally deciding to rebuild the carb I removed the gas line from the carb and ....nothing. Barely a trickle. Something was stuck in the line ahead of the filter. I removed line and filter. Blew it all out. Reassembled. And off to the races!! I was so damn excited I did my, AND my neighbor's driveways.

"What's got into HIM?" he wonders

nbpt100, I will load some pics. This is an ancient toro 724 from the 70's passed down from my older brother who took great care of it. It's been through the war in Michigan. That idlerwheel-on-plate 3 speed transmission is a marvel of simple longevity.

I top to bottom rebuilt this thing about 5 years ago. Replaced wheel, auger, and impeller bearings with pillow block ball bearing units. Put a zerk fitting on the auger worm gear housing and pumped axle grease into it until it burst out of every seal. Good for bronze worm gears? Who knows? We're on a roll here. Tig welded reinforcement at the weakened bases of the auger times.

Repowered it with a Tecumseh OH 318 ea 11hp OHV that I bought for 120USD brand new +ship. Can't remember how much I paid for ship. Astonishingly, the same website still has these in stock for the same price. They don't sell because they have tapered shafts meant for obsolete and unpopular Campbell Hausfield generators so no one thinks they can use them. But the taper is only an extension of the otherwise standard sized shaft. I just ran the engine clamped to my work bench and sawed the tapered section off with a hacksaw. Easy. Five minutes. The Toro dual pulley slid right on. Lacking a keyway on the section that was left I just ghetto rigged it with a couple of tac welds on the outboard side to secure it. The dual pulley is a massive heat sink. Did I damage the oil seal with heat? No I didn't. Stop nit picking. It's held fast for five years now. Easy to grind off the tac welds if I ever need to.

If there was a hitch I'd say it was the carb. The emissions regulated plastic bodied carb that shipped with the engine was a NIGHTMARE!
Fortunately I have a good supply of spare parts in my shop/dungeon. So I unboxed a "vintage" spare carb from a 12hp briggs I had on the shelf...old school with the adjustable main jet screw under the bowl, and fitted it to the Tecumseh. Night then...day! For modern 4cycle utility engines NOTHING screams inconvenience more than the omission of a user adjustable main jet. I get it. Most people should not be fu@@ing with it. If the motor is running badly then it probably needs professional help, not some idiot just band-aiding the problem with a mixture tweak. But for those of us that need more control.... like fitting a non oem carb to a different motor, an adjustable main jet is a godsend.

 

[frascati]

oh, and, the best non stick coating I've found so far after many experiments is a spray/mist bottle of decent quality mopable floor wax. There are a hundred brands but basically just a watery viscosity white liquid that sprays well and dries/hardens ready for 'use' within an hour. Formulated to withstand foot traffic it holds up well to snow. My garage is heated so I just respray the parts exposed to snow the next day with a little misting.

It's practically made for this job.

 

[theoldwizard1]

Now I had an issue with a 10hp Tecumseh with this setup and the hose was restricted. Idle and operating speed were fine but if I dug into heavy snow the bowl would run dry. It wasn't OEM hose but something thicker.

Most people don't know this. The standard 1/4" ID fuel line you buy at an auto parts store has a LARGER OD than the typical fuel line used on small engines ! Tygon (the funny green/yellow hose you find on chain saw engines) comes in various IDs and all of it has thinner wall than neoprene hose