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View Full Version : OT: Odd snowthrower problem and cure



CarlByrns
03-12-2014, 07:14 PM
OK- we are in the grips of a winter storm that has dumped about 10 inches of snow so far. When I got home from work, I pulled the trusty Toro two-cycle snowthrower out, it starts on the first pull as always and then I start cleaning out the driveway. After about ten minutes, the engine loses power and -puff- dies. It restarts but has no power at all.

I dragged the machine back into the garage and, suspecting a clogged main jet, pull the carb bowl off. Everything looks good, but I clean the jet out anyway.

Back outside- same results. Runs fine, then poops out.

In the garage, I started tinkering with the governor linkage- there is an air vane that pulls the throttle shut, and a spring that pulls it open. Ah-ha! The linkage is binding so that the engine can't power up. I sprayed the linkage with carb cleaner, but it doesn't help.
Next, I pulled the carb off to check the butterfly. Its nice a free, as is the air vane and linkage. WTF.

I put the carb back on and tightened the mounting screws, working the linkage as I go. When the screws are nearly tightened, the butterfly sticks.
After pulling the carb off- again- I noticed that the carb flange gasket doesn't look right. Sure enough, the gasket has softened, changing the clearance between the carb and the intake pipe (which the butterfly is hitting and binding). I made a new gasket out of sheet stock that I keep on the shelf, put everything back together and now it runs like gangbusters.
I believe the butterfly was just missing the intake pipe when cold, but binding when warm.
What an odd failure!

Wayne Sippola
03-12-2014, 07:51 PM
That's a new one to me. Nice deduction of the problem - but you probably could have used a bigger snow blower this year anyways, and you just ruined the perfect excuse!

lynnl
03-12-2014, 08:09 PM
Toro makes a good engine. I once had a Toro two cycle lawn mower. Had it stored under a crawl space and got heavy rains so it was under water for about a week. Pulled the spark plug, drained and cleaned the fuel tank and carb, and it cranked right up and ran fine.

Dave P.
03-13-2014, 11:02 AM
Carl,
Long time Toro dealer here....it's a common issue with the plastic bodied carbs on some units.
As soon as the engine warms up a bit it, will bind the butterfly shaft, the tighter the mounting screws
the worse it gets.
You can try pulling the shaft and reaming the bore a bit....may help.
In a service shop situation we just replace the carbs. The new ones are cast bodies.
Our experience has been it's not the butterfly hitting but rather the shaft binding.
You can sometimes heat the carb with a heat gun and see/feel it.
Dave

dneufell
03-13-2014, 04:09 PM
great tech tip! Thank you.... I have a few (4) of them Toros for my girlfriend. She prefers them over the heavy 2 stage snowblower.

MotorradMike
03-13-2014, 04:21 PM
Mine acted up today as well.
Started backfiring as I was putting it away, I sure didn't want to work on that thing in the Winter. Trouble went away in a few hours, I have no idea what the trouble was.
In the Spring, which I fully expect by June, I'll change the plug and air filter.
Not a great wrench on small engines.

Today was the most Wintry I've seen in 20 years, the roads were white and banks were high.

krutch
03-13-2014, 07:15 PM
Mine acted up today as well.
Started backfiring as I was putting it away, I sure didn't want to work on that thing in the Winter. Trouble went away in a few hours, I have no idea what the trouble was.
In the Spring, which I fully expect by June, I'll change the plug and air filter.
Not a great wrench on small engines.

Today was the most Wintry I've seen in 20 years, the roads were white and banks were high.

Ain't ya glad all those taxes we've been forced to pay to our various governments fixed global warming?

CarlByrns
03-13-2014, 08:37 PM
Carl,
Long time Toro dealer here....it's a common issue with the plastic bodied carbs on some units.
As soon as the engine warms up a bit it, will bind the butterfly shaft, the tighter the mounting screws
the worse it gets.
You can try pulling the shaft and reaming the bore a bit....may help.
In a service shop situation we just replace the carbs. The new ones are cast bodies.
Our experience has been it's not the butterfly hitting but rather the shaft binding.
You can sometimes heat the carb with a heat gun and see/feel it.
Dave

Well, I've put about 30 minutes of moving heavy snow on it with no issues. Since the snow is still coming down and the machine is working, I'm calling that a win.

Given that this is a 9 year old machine (38515 S/N 25XXX) and this problem has never happened before, I'm still inclined to blame the spongy gasket- maybe its allowing the carb body to warp.

I'll heat the carb when the snow is gone and see if it binds. If it does, I'll ream and bush the shaft bore.

I work for a Toro Commercial Distributor and even at my cost, a new carb ain't cheap.

CalM
03-13-2014, 10:23 PM
Not directly related, But the SYMPTOMS were the same.

I was using a Toro walk behind to clear snow off a deck and the unit would throw the snow just fine for about 5 minutes or so.
Then the engine would start choking down, losing power, coughing and sputtering. Soon it would die alltogether.

While trying to restart, all the usual "stuff" was looked to. Spark? OK, fuel? OK, dri-gas?, fuel filter?, fuel tank vent? all OK. But after all the checking and dicking around and about 100 pulls on the starter rope, the engine would start again . Only to repeat the failure in about five minutes of operation. If allowed to just sit and run, the engine did so without a hitch. It was only when called to actually blow snow did the trouble arise.

This went on for several snow removal efforts, and the same report was made by others who tried to use the machine at other times.

The last time I used the blower, I checked to see if the air cleaner was clogged. There was no air cleaner fitted under the cover! And the bore of the carbie was iced up tighter than toby's touch*****

Seems that the fresh blown snow was being caught up in the intake air, causing carb icing , only to melt away after the engine heat soaked in. Allowing the engine to restart and repeat the entire frustration.

Note: the blower is assigned to clear snow from the deck of building with changing staff, including "volunteers" like me, hence the various "operators")

So... sometimes, the trouble "escapes" due to temperature changes, but it's not mechanical.

Just a heads up.....

CarlByrns
03-13-2014, 10:57 PM
The last time I used the blower, I checked to see if the air cleaner was clogged. There was no air cleaner fitted under the cover! And the bore of the carbie was iced up tighter than toby's touch*****

Snowblowers almost never have air cleaners. Apparently, the theory is that winter air is pretty dust-free and the typical paper filters would clog with snow.

Snowthrower engines always have some form of carb heat. Four cycle machines use a box where the air is heated by the muffler (and when the old muffler rusts out, you can't just stuff a generic one on the engine. Don't ask me how I know this.) Two cycle machines usually have some kind of ducting directing warm air from the cylinder over the carb.

Dave P.
03-13-2014, 10:58 PM
Well, I've put about 30 minutes of moving heavy snow on it with no issues. Since the snow is still coming down and the machine is working, I'm calling that a win.

Given that this is a 9 year old machine (38515 S/N 25XXX) and this problem has never happened before, I'm still inclined to blame the spongy gasket- maybe its allowing the carb body to warp.

I'll heat the carb when the snow is gone and see if it binds. If it does, I'll ream and bush the shaft bore.

I work for a Toro Commercial Distributor and even at my cost, a new carb ain't cheap.

It's good that it's working, I'm damn sick of winter, but afraid it's not over yet.
I could see that gasket warping the end of the carb a bit and adding to a binding issue.
Next time we see one I'll get a look at it myself.
Regarding air filters on snowblowers....never seen one.
Dave

Dave P.
03-13-2014, 10:59 PM
Duplicate post...deleted.
Dave

CalM
03-13-2014, 11:11 PM
Snowblowers almost never have air cleaners. Apparently, the theory is that winter air is pretty dust-free and the typical paper filters would clog with snow.

Snowthrower engines always have some form of carb heat. Four cycle machines use a box where the air is heated by the muffler (and when the old muffler rusts out, you can't just stuff a generic one on the engine. Don't ask me how I know this.) Two cycle machines usually have some kind of ducting directing warm air from the cylinder over the carb.

"Always have" and "have a sufficient" carb heater must have escaped the Toro designers ;-)

Ice in the throttle bore is conclusive evidence of an insufficient design easily rectified by fitting a particulate filter. (snow being the particulate form of water ;-)

Willy
03-13-2014, 11:14 PM
Most dedicated 4 cycle snow blower engines are different than there warm weather brothers in several ways.
In the context of this discussion the key difference is that the exhaust port is closest to the cooling fan and the intake port. The carburetor and air intake is down stream of the heated air from the exhaust system. In conjunction to the carb being down wind of the exhaust port and muffler heated air, there is also a sheet metal shroud around all of this in order capture and retain as much of this warm air as possible.

All of the snow blowers I've ever used at least had this system and also did not utilize an air cleaner. I have never experienced an ice build up in the carb or air intake so the system must work.
A neighbor of mine seeing that I had no air cleaner on my snow blower insisted that I install one so that I would not dust the engine.
I told him that if I get dust in the engine....I'm doing it wrong.:)

CalM
03-14-2014, 12:21 AM
Most dedicated 4 cycle snow blower engines are different than there warm weather brothers in several ways.
In the context of this discussion the key difference is that the exhaust port is closest to the cooling fan and the intake port. The carburetor and air intake is down stream of the heated air from the exhaust system. In conjunction to the carb being down wind of the exhaust port and muffler heated air, there is also a sheet metal shroud around all of this in order capture and retain as much of this warm air as possible.

All of the snow blowers I've ever used at least had this system and also did not utilize an air cleaner. I have never experienced an ice build up in the carb or air intake so the system must work.
A neighbor of mine seeing that I had no air cleaner on my snow blower insisted that I install one so that I would not dust the engine.
I told him that if I get dust in the engine....I'm doing it wrong.:)

Calling it "just doing it wrong" doesn't get the snow off the deck ;-)

perhaps there are some baffels or other important parts missing, It is not my concern, I;m just relating the fact that carb icing brought on symptoms much like the OP's.

Might be something to it. Have you ever experienced such troubles with your blowers?

If so, Chime in!

Willy
03-14-2014, 12:51 AM
Calling it "just doing it wrong" doesn't get the snow off the deck ;-)

perhaps there are some baffels or other important parts missing, It is not my concern, I;m just relating the fact that carb icing brought on symptoms much like the OP's.

Might be something to it. Have you ever experienced such troubles with your blowers?

If so, Chime in!

Cal, when I said "doing it wrong" I was being facetious. LOL
I mean really, if you are using a snow blower and you're getting dust into the engine...well you know..........

In over 40 years of using snowblowers with heated air intakes, and I'm talking units from 5-500 HP, no never a problem with intakes freezing up if the system is functioning as designed.

Unlike a summer application though where particulate filters or pre-cleaners are very effective, I cannot envision this type of system to work for an application of this type.
Because of the shear volume of particulate that one has to trap when snow/ice dust is allowed to be ingested into the engine's intake air stream it simply would not be practical.

The engine's combustion air intake should be not only shielded from the ingestion of snow/ice, but it should also be pre-heated to prevent carburetor icing.