MTD Snow King only runs with choke on

[prorec]

Hello. I have an old MTD Snow King (circa 1970) snowblower that will run only if the choke is at the halfway position. It starts on 2-3 pulls and it will throw snow but it lacks full power. It seems to run a bit fast and will quit if the throttle is closed too much or if the choke is off. It doesn't hunt for the correct RPM.

I have cleaned the carburetor and installed a complete rebuild kit. I also have adjusted the screws to factory specs and tried to further adjust them with the engine running but it didn't help.

As far as I understand it the problem is likely an air leak or the fuel is being restricted. Since I have cleaned the carburetor, fuel tank and fuel line I think it may be the throttle shaft that is leaking air.

With the engine running I sprayed WD-40 around the intake gasket and throttle. The engine speed increased when I sprayed around the throttle only. It will also increase when I spray into the choke. The carburetor is a Wabro LME.

The thing that puzzles me is that the throttle shaft doesn't "seem" to be loose. It will move up and down a little but it's firm when turned from side to side. Is this little bit of play enough to allow a substantial air leak that would cause the engine to quit with the choke off? Thanks for any replies.

 

[awlchu]

Does the carb have a mounting flange? It is possible the flange is warped. If you have a piece of glass, check for flatness.

Some wet-dry snadpaper and WD-40 lube, you can true of the flange. BE CAREFUL, only slight pressure is required to remove the soft cast AL mat'l on the flange.

 

[prorec]

Thanks for your reply. I'm not sure what you mean by the mounting flange. I installed a new gasket where the carburetor mounts to the intake. With the engine running I sprayed WD-40 all around that gasket but the engine didn't speed up so it seems it's not drawing in air there.

I also sprayed the WD-40 around the throttle and the engine did speed up, so it seems to be drawing air in around the throttle but is that air leak enough to make the engine quit without the choke on?

 

[mainiak1]

You said you rebuilt the carb. I'm assuming you replaced the jet or took it out and cleaned the orifice. I had the same problem several times and it was a partially plugged jet.

Just a thought.
Mainiak1 /forums/images/graemlins/confused.gif

 

[prorec]

I did replace the main jet adjustment needle and cleaned the orifice. There is a slotted brass fitting where the needle seats but I didn't remove it. I sprayed it with carb cleaner and pushed a plastic pick through to clean it. I will try to remove that fitting and see if there is more dirt. Thanks for the tip.

 

[mark1]

Hi..Lots of times these old engines seem like they have a fuel problem and it turns out to be ignition..Have you ever installed new points? poor ignition,lack of power,needing "Choke" backfiring, many times are old worn out points..sometimes even a partially broken flywheel key,will act similar as it changes the ign timing..Let us know. /forums/images/graemlins/blush.gif

 

[HammerFour]

With it requiring partial choke to run, it sounds like a plugged jet or plugged fuel passage. The carb body may need a soaking in a carb cleaner to get the internal passages clean.

 

[prorec]

Thanks; I hadn't considered the ignition since it starts right up. I will have a look at the points and flywheel key. I did remove the spark plug and ground it to have a look at the spark (at night) and it seemed pretty good. Might be different when running though. I will check further.

(I'm assuming you don't think the throttle air leak could be the culprit.)

As far as soaking the entire carb, I thought that might be the next step if the throttle wasn't bad.


I have cleaned every passage possible so the only other thing to try regarding a fuel problem is soaking the carb.

The rebuild kit I bought came with a tiny rubber O-ring but there isn't one on this carb. Is it possible that the idle mixture screw should have one? Maybe that is a possible air leak too.

I did take out the slotted brass fitting I mentioned above. It was very clean. There are several small metering holes in the fitting and they were all clear.

Back to work. Thanks a lot.

 

[TWINKLE_TOES]

prorec, is it possible when you say you spray the throttle with WD40 that you may be spraying the head and what you have is a head gasket leak?

 

[prorec]

I suppose it's possible but I don't really think so. I used the red plastic straw to control the spray and was pretty careful where I sprayed.

I could try spraying the head gasket just to see what happens though; great idea.

The carb is off right now so when I get it back on I'll try it and post on what I find. Thanks.