Troy Bilt Snow Blower - Engine Surging

[Hammermechanicman]

Hey, i hit something with my new mower and now it shakes real bad. You will fix it under warranty. Right?
Hey, i left the key on for a few days on my new mower. Battery is dead. It's under warranty isn't it?
Hey, i forgot to put oil in the new mower and it locked up. I did put oil in after the fact to fool you. Should be under warranty I'm sure.
Hey, i hit a tree because this new mower turns too tight and broke the hood. Warranty repair isn't it?

 

[AVB]

When an engine is running without a load it is actually drawing fuel from the idle circuit of the carb. But because the idle circuit in your carb in clogged the engine is is slowing down due to lack of fuel which then the governor spring pulls the throttle to run faster which exposes the high speed jet of the carb to the low pressure air in the carb, and then slows back down after getting a gulp of fuel. When you put a load on the engine the engine governor tries to maintain the engine speed, and in doing so gets fuel from the high speed jet.

+1

There is also one other possibility that I have seen and that is the idle speed itself can be set too low; therefore the starves for fuel as even the idle bleed circuit is partially blocked by the throttle vane.

But as noted if it started surging after sitting over a month a carburetor cleaning is recommended first as fuel does evaporate leaving the additives behind plugging the tiny fuel passages in the carburetor. Ethanol fuel have a lot more of these additives plus the alcohol attracts moisture from the air which it more prone to causing problems but non ethanol fuel also have additives just not as much so both can cause problem if left unused for extended peroids.

 

[AVB]

Hey, i hit something with my new mower and now it shakes real bad. You will fix it under warranty. Right?
Hey, i left the key on for a few days on my new mower. Battery is dead. It's under warranty isn't it?
Hey, i forgot to put oil in the new mower and it locked up. I did put oil in after the fact to fool you. Should be under warranty I'm sure.
Hey, i hit a tree because this new mower turns too tight and broke the hood. Warranty repair isn't it?

I haven't read a warranty yet that covers stupid things. Most don't cover anything other than factory defects in materials and workmanship plus most warranties are written in such a way that technically everything is not covered. Basically it is only warranteed until up start it up or the warranty period expires which ever comes first.

 

[l008com]

Update!!

I finally got around to ordering a new carb. $10 shipped off ebay. I threw it on tonight and it immediately ran like it was brand new. Started right up, ran great, lowered the throttle to idle and it idle'd great. So as far as that main problem, mission accomplished!

But I had a slight problem during reassembly
Spare parts! I looked close and watched videos and could not find where these parts go!
The loop looks like it would go in the belt area, but the video I watched had no such loop. But then it was a similar model but not the exact same model so I'm not sure.
And the two screws, they may or may not be the screws that keep that loop bolted down. They look like they are similar to the screws holding the outer body panels on, but they are longer. And I looked everywhere and couldn't find any 'missing' screws. Unfortunately I had to leave the blower disassembled for a few weeks while I waited for the new carb. Just long enough to forget where everything goes!

 

[Ken Kegris]

It is in the low speed circuit, Remove the idle speed adjusting screw and look stright under where you took that screw out and you will see a black pc of plastic or a phillips screw. gently remove the plastic pc and clean the jet I think it is about .013 hole size and then blow it out the jet is the pc of plastic. Now if you have the phillips screw type you remove the screw and then with the 013 cleaning tip reach down in and clean the brass jet. Sometimes this is very hard to get to with the carb installed.

 

[l008com]

I'm not convinced it was the low speed circuit. While my original post said it ran fine under load, that was only after the first snow storm. As time went on, it would run poorly under load too. Still much better than when idle, but definitely not normal.

Also I've already replaced the carb with a new one and that problem is long gone.

Also regarding my spare parts, I looked through a bunch of parts lists and couldn't find that metal loop. I watched video after video until I finally found one that had it! So now I know where that goes! And I suspect the two extra bolts go on the inside of the airbox area. So next time I have a few hours to work on it, that beast should be good to go.

 

[l008com]

Follow-up follow-up: Everything is back together properly and the machine is running great. The wire loop went where pictured in the previous post, and the two bolts were part of the airbox. Now we just need some snow.... wait I mean heat waves.