Rust in carburetor?

[climbstihl]

I just noticed rust in the area of the carb where the impulse line comes in. Is that something to be concerned about? It doesn't appear to be clogged because of that.
I also noticed a small hole in the cover on the metering side. I'm not sure that's supposed to be there.
The carb is a Walbro WT-22B, off of my 026. I took a look at it because the saw would flood after letting go of the throttle. The carb kit was recently replaced, the carb is original.

 

[Rob Stafari]

I'd hit it with some carb cleaner and scotch brite and call it good enough. My only concern would be the question of why it is there. Shouldn't be any rust in a chamber filled with oily fuel. Did it sit for a long period of time or get some water in fuel tank?

As far as flooding after a carb rebuild... did you set the metering lever height when you put the kit in? Too high or too low and it won't run right.

 

[Matthew Stone]

That appears to be sludge from ethanol gas to me. It's different colors depending on premix brand/colors.

 

[climbstihl]

I'd hit it with some carb cleaner and scotch brite and call it good enough. My only concern would be the question of why it is there. Shouldn't be any rust in a chamber filled with oily fuel. Did it sit for a long period of time or get some water in fuel tank?

As far as flooding after a carb rebuild... did you set the metering lever height when you put the kit in? Too high or too low and it won't run right.

I don't know the history of the saw and carb, I've only had it for about 3 months.

The flooding didn't start right after the carb rebuild, and I didn't rebuild it, so I don't know if the metering lever was set correctly, And I don't have a way of checking. I think it might be set to high, or the seat or needle is damaged, but they looked alright.

 

[climbstihl]

That appears to be sludge from ethanol gas to me. It's different colors depending on premix brand/colors.

No, it's definitely rust.

 

[Tom Dunlap]

Metal gas can?

 

[Birdyman88]

Metal gas can?

If this is it, then I would definitely change cans.

Otherwise, It's probably just from ethanol/water interactions of a sitting saw with the steel inside the crank case and cylinder like crankshaft, bearing, etc. Clean it and don't worry about it.

 

[Tom Dunlap]

It's probably just from ethanol/water interactions of a sitting saw with the steel inside the crank case and cylinder like crankshaft, bearing, etc. Clean it and don't worry about it.

How can there be any 'interaction' consequences showing up there? Isn't this upstream from the air/fuel flow? Maybe I'm missing something.

Going wayyyyyy back to the days of running leaded gas the gunk in the pic looks no different than what I've seen in almost every carb I've opened up. Most of those years were with using plastic gas cans. Who knows what dirt and crud from around the fuel plug might be washed into the tank during refueling?

 

[Matthew Stone]

I believe in the moment of backfire or flooding there is fuel rich pressure on the filter side.

 

[Birdyman88]

Direct route from crankcase to impulse port on carb where the rust is showing. Pressure-vacuum cycle could cause some migration if there was any rust in crankcase. Saw would have to have sat for a while and had some water contamination though.

 

[Tom Dunlap]

I think I understand...LOL

Will you open the carb in a month of use to see if more gunk shows up?

 

[Birdyman88]

Will you open the carb in a month of use to see if more gunk shows up?

Yes. This is TreeBuzz and we must have resolution. All those other sites leave ya hangin'.

 

[climbstihl]

Maybe someone used a metal gas can before, but not in the time I've had it.
I have to get it running before being able to use it for a month and inspect it then.

 

[Rob Stafari]

They make a tool to check metering lever height, but you don't need it for most. Just a straight edge.

Should be flush with the bottom of the bowl at rest. Just bend it up or down, whichever it might need, if it is not. Check there first, a lot of people don't know to adjust accordingly and just throw the kits in.

 

[climbstihl]

Thanks, I knew about the gauge, was thinking about getting one at the dealer's tomorrow, I didn't know you could use a straight edge across the bottom.

 

[Matthew Stone]

I was looking today and found a new carb for 026/028- it does indeed have the small hole. I couldn't see on mine and didn't really want to pull the carb.. but I was curious enough that it was already in the basement.

 

[climbstihl]

I was looking today and found a new carb for 026/028- it does indeed have the small hole. I couldn't see on mine and didn't really want to pull the carb.. but I was curious enough that it was already in the basement. View attachment 64778

Thanks, that good to know. it seemed really out of place to me...

 

[Matthew Stone]

I agree! I didn't remember it there, seems so strange that they're both kind of rough also, for a factory item.

 

[Birdyman88]

I also noticed a small hole in the cover on the metering side. I'm not sure that's supposed to be there.

I just noticed you asked about that hole. That is the pressure relief hole for the metering diaphragm. Just like the impulse line pushes and pulls on the fuel pump, the metering diaphragm has to has an air relief to keep from building a vacuum or pressure (during the impulse cycle) on the dry side. Without that hole, vaccuum and pressure on the dry side of the metering diaphragm can interfere with the proper movement of the diaphragm.

On some carbs, they have a port built into that cover that interconnects back to the breather. If you have that port, you can just switch it over to your new carb that has only that little hole.

 

[eyehearttrees]

How can there be any 'interaction' consequences showing up there? Isn't this upstream from the air/fuel flow? Maybe I'm missing something.

Going wayyyyyy back to the days of running leaded gas the gunk in the pic looks no different than what I've seen in almost every carb I've opened up. Most of those years were with using plastic gas cans. Who knows what dirt and crud from around the fuel plug might be washed into the tank during refueling?

Good post thanks!! I'd been blowing-off my plugs/caps before filling oil/fuel but now whenever possible I simply hit it w/ brake-cleaner before opening (am I using brake-cleaner properly that way? My understanding is I use my carb-cleaner spray for anything that'd take oil, since it leaves an oily residue, and the brake-clean spray for everything else!)

It's amazing what a % of 2-stroke problems are due to fuel, hell I got a 125b Husqv blower, like-new condition, for free because someone had curb'd it over nothing more than bad gas! I'd used eth.-free gas + synthetic oil for the past ~6mo but just bought my 1st canister of pre-mix, couldn't find MotoMix anywhere local so got "SEF" brand, pretty odd in that it says it's for BOTH 40:1 and 50:1 engines but in-practice I was using 45:1 for everything anyways, just for convenience But after all I've learned & fixed I am now sold on only using pre-mix in my gear!!!