Mechanic’s Grind

A few months back, I picked up a Jacobsen Sno-Burst on Craigslist for $20. Surprisingly enough, it ran when I got it home. I used it happily for the first half of the season and had no problems up until today. I was slogging my way through the five inches of slush that was dumped on Milwaukee last night when the thing just died. It wasn’t its normal bog-out-and-die, it was just pum-te-pah—dead. Well, as normal, I ripped on the cord a couple of times. Unlike normal, I got nothing. After a little common troubleshooting, I determined that I was going to have to tear down the carburetor. I figured I could go online and get myself a manual, but found no such luck. Since there was no such luck, I figured I would fill the void. Please read this whole guide before starting work. It’s written in my order of operations and I came upon better ways of doing things part way through.

This is a Jacobsen Sno-Burst. If your snowblower looks like the one in the picture, then you’re probably in the right place.

The first thing you need to do is take off the top cover. In the case of my old beat-up unit, there was only one screw holding the cover on. I took it out and had a look at the engine. The carb is the little metal box on the front left from the driver’s position. On initial inspection, it looked like it was going to take some wizardry to get the carb off, but I think I handled it pretty easily.

Before you can do much else, you have to detach the paraphernalia from the carburetor. The choke cable is removed by simply unscrewing the phillips head screw that secures the cable, then weaseling the little hook out of its eye-hole by hand. If your machine has been in service as long as mine has, the fuel line is going to be a pain to remove.

(Don’t forget that you’re going to have gas running out when you disconnect / puncture the line. Even if you siphon out the tank, you’re never going to get the gas that is in the line itself. I chose not to siphon out the tank, but rather had a connecting hose on hand to let the gas run into a collecting tank.)

Unscrew the hose clamp and get it out of the way. I wound up using a pair of vice-grips and ripping the fuel line apart to get it off. Even so, it left a chunk of line still on the tap that I had to cut off with a pair of dikes. Other than being fused to the tap, the fuel line was in great shape and plenty long, so I just used a sharp knife and fashioned a new end for it.

I decided that the best approach for carb removal would be to remove the carburetor and flange assembly intact from the intake body. There are two 3/8″ bolts that hold the flange to the intake body. Unfortunately, there is a little bit of difficulty getting to them. On the left side, the galley cover is in the way. (In the picture, you can also see the clear tube running from the fuel line to my collecting tank.)

On the right side, the diaphragm cover is in the way.

There isn’t a lot of room to work around the engine so getting the galley cover off required the use of a simple jig that I assembled out of a 3/8″ box-end wrench and a flat-blade screwdriver bit from my hand impact driver.

Once the galley cover was off, there was just enough clearance to fit a socket over the left-hand flange bolt.

To remove the diaphragm cover, I used the long, flat-blade screwdriver that I use to tune the carbs on the bikes.

Once the diaphragm cover is off, there is clearance to get a socket over the right-hand flange bolt as well.

Although you can get a socket on the bolts, there is no way that you’re going to get a socket wrench in the tight space, so once again I made a little jig. This one is a 1/4″ wrench, a 1/4″ hex-to-square adapter for a multi-bit screwdriver, and a 1/4″ drive, 3/8″ socket for the bolts.

Once you’ve got the bolts out, you may think you’re home free … but you’re not. The automagic throttle is still connected to the bottom of the carb. The linkage between the vacuum actuated throttle and the carburetor is flexible plastic, so you can flip the carb over with it still attached to get access to the circlip that holds it on.

The circlip (like all snap-rings) is a pain in the ass to get off. A circlip remover won’t even help you as there are no attachment dimples and the ends are too far apart to use inverse pliers. I lucked out and after a while one end of mine jammed in its galley so all I had to do was jam my trusty carb-tuning screwdriver into the circlip galley and pry out the other end.

As of now, you should be able to remove the carb from the engine completely and take it to your bench.

Be sure to put the flange bolts somewhere where you won’t lose them.

At this point, you should make sure that both your choke and throttle butterflies work easily as expected.

Also, the fuel tap may fall out. This is no big deal as it’s just a press-in part. Just be sure to put it back later.

Before we can really clean anything, we need to get the diaphragm out of the way, mostly to avoid damaging it. I had no intention of replacing the diaphragm, so I used a very sharp knife to slowly work around the edges and separate the diaphragm gasket from the carb surface. This takes time and patience. If you cut or tear the diaphragm, you’re looking at hard-to-find new parts.

Once you’ve got the diaphragm loose all the way around, you’ll notice that it’s still connected in the middle. This is the connection to the “float needle”. You can safely bend the diaphragm back a little bit so that you can see which way you need to slide it to disengage the needle. Don’t worry, nothing is going to fall out.

Once you’ve got the diaphragm off, you can start honestly cleaning the carb. Spray carb cleaner or WD-40 into every hole you can find (you need the straw) and make sure it comes out somewhere else. Pay special attention to the big hole at the bottom of the carb. That nasty brown thing is a fuel strainer. It may fall out on its own; you may need to help it with a wire or screwdriver. Clean it well and make sure the passage below it flows. Don’t forget to put the screen back when you’re done.

The trickiest and most important (read: likely to get clogged) are the tiny holes in the track above the diaphragm. One of them connects to the “bowl” under the diaphragm. The other connects to the main air passageway where the butterflies are. Make absolutely sure that these flow as they should.

That’s really all there is to cleaning the guts of the carb. If you want to separate the flanges, you can do so by taking out the two big screws by the choke butterfly.

Because of this separation, you can reattach the flanges to the engine first, and then attach the carb to the flanges with the two screws. I didn’t trust myself to line everything up well enough, so I just assembled in the reverse order of removal.

First, I reattached the flanges to the carb assembly.

Next, I reattached the diaphragm to the needle.

Next, I reattached the throttle and circlip taking care to twist the throttle linkage such that it would be properly oriented once the carb was righted.

Next, I righted the carb and bolted it back to the intake with the flange bolts, taking special care not to hurt the diaphragm which is now only loosely attached to the carb.

Next, I screwed on the diaphragm cover using my carb-tuning screwdriver.

After that came the galley cover with the screwdriver jig …

Finally, I reconnected the choke cable and the fuel line. (I forgot to take a picture with the fuel line connected. You get the point.)

Put the cover back on, put some premix in and give her a rip. Mine fired right up and ran like a dream. I hope you can say the same.

Carburetor Cover?
Evidently, these machines had a carb cover from the factory. Mine was gone when I got the machine, but Tom was nice enough to send me some pictures of his:

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