Mac 10-10 automatic 600002U, Walbro SDC, throttle issues

[Gmn1996]

Long story short, saw won’t hold RPMs at full throttle. Starts first pull, idles properly, drops RPMs while throttling up. Both the high and low jets are set to a point where the low is rich enough, and the high is maybe a full turn from being maxed. Any leaner on the high and the saw drops rpms on the high end. Fuel line has no cracks.

Is this a case of a possible vacuum leak? Gummed jets? A possible carb kit needed? It’s a fairly new carb.

Also, spark and air are fine.

The carb isn’t the original carb that they put on it back in the day, it was a Tillotson HS series (85720). The Mac 10-10, 600001 came with the Walbro SDC, is that a possible issue? Or are these saws possible of swapping parts like legos?

I’ve got videos of it running, throttling up and whatnot, if that might help diagnose the issue.

Any feedback would help, thanks!,

 

[Mad3400]

I was having the same issue, I pulled the Carb off and tore it all apart, cleaned every hole and port with carb cleaner.

I put it back together, Re-Tuned it and went through a few tanks, then happened again.

I pulled it apart again, found that it got clogged with a bunch of crap and fine saw dust. Turns out my fuel filter fell off.

Cleaned it the same way as I mentioned above, put it back together, Re-Tuned and has been running Great ever since.

Make sure after cleaning the carb to gently blow out the fuel line and make sure fuel filter is good.

Hope this helps,

Mad3400

 

[Mad3400]

Also, the Air Filters aren't great on these, so as soon as you notice the chain getting dull, Touch it up or swap the chain out.

Mad3400

 

[Gmn1996]

I was having the same issue, I pulled the Carb off and tore it all apart, cleaned every hole and port with carb cleaner.

I put it back together, Re-Tuned it and went through a few tanks, then happened again.

I pulled it apart again, found that it got clogged with a bunch of crap and fine saw dust. Turns out my fuel filter fell off.

Cleaned it the same way as I mentioned above, put it back together, Re-Tuned and has been running Great ever since.

Make sure after cleaning the carb to gently blow out the fuel line and make sure fuel filter is good.

Hope this helps,

Mad3400

Thanks for the reply!

I’ll give it a shot, I’m planning on tearing it down completely but I’m fairly new to this. Bought it to learn and hopefully run at work.

 

[heimannm]

Check the condition of the fuel line and the filter inside the tank. The filter might be plugged and/or the fuel line may be so soft it collapses on itself.

Carburetors are interchangeable so that should not be the issue. Do check the condition of the carburetor diaphragms, everything might look good from the outside but the diaphragms might be stiff.

Mark

 

[Gmn1996]

Check the condition of the fuel line and the filter inside the tank. The filter might be plugged and/or the fuel line may be so soft it collapses on itself.

Carburetors are interchangeable so that should not be the issue. Do check the condition of the carburetor diaphragms, everything might look good from the outside but the diaphragms might be stiff.

Mark

Thanks for the reply Mark!

I was told if the fuel line was stiff, that’d be an issue. It seems relatively new, squishy and no obvious signs of damage. I’m going to pull it off and clean it out. Also going to pull the tank and check that out as well, thanks for the advice!

 

[Mad3400]

Also keep I'm mind the Configuration & Order for each gasket when disassembling the Carb.

The 10-10 is a Great saw to learn on.

Mad3400