Anyone want to help me with a mini mac? Carb problem

[Deegore]

It's a top handle McCulloch mini mac 35.
Got the saw for free. It ran great. Started on the second pull. Lots of power for its size.
The problem was when it ran out of gas it wouldn't start again until it sat for a half hour.
I took it apart and found the fuel line was cracked. I figured I'd put a carb kit in it since it's kind of a pain to take apart.
Now it runs for a couple minutes and dies. I think the crank case is filling with fuel. The spark plug is wet and a little fuel sprays out the muffler as I'm pulling. If I drain the fuel, pull the muffler off, set the piston at the top, and set it in the sun for a half hour it will start again and run for a couple minutes.
My guess is the needle isn't seating. It's a walbro mdc carb. The instructions I got say the metering lever should just touch a straightedge placed on the carb body. I tried setting it lower but it didn't make a difference.
Any ideas what I'm doing wrong?
I replaced the Welch plugs. If they aren't sealing would that explain the problem?

 

[lone wolf]

It's a top handle McCulloch mini mac 35.
Got the saw for free. It ran great. Started on the second pull. Lots of power for its size.
The problem was when it ran out of gas it wouldn't start again until it sat for a half hour.
I took it apart and found the fuel line was cracked. I figured I'd put a carb kit in it since it's kind of a pain to take apart.
Now it runs for a couple minutes and dies. I think the crank case is filling with fuel. The spark plug is wet and a little fuel sprays out the muffler as I'm pulling. If I drain the fuel, pull the muffler off, set the piston at the top, and set it in the sun for a half hour it will start again and run for a couple minutes.
My guess is the needle isn't seating. It's a walbro mdc carb. The instructions I got say the metering lever should just touch a straightedge placed on the carb body. I tried setting it lower but it didn't make a difference.
Any ideas what I'm doing wrong?
I replaced the Welch plugs. If they aren't sealing would that explain the problem?

Is the needle sealing? Check to see if it shuts off with the carb out.

 

[HarleyT]

Needle!!!!!
Get a full oem kit, polish the seat with a q-tip and baking soda.

 

[lone wolf]

Skip ahead to about 4 minutes

 

[HarleyT]

Skip ahead to about 4 minutes

My wife always says that........

 

[lone wolf]

My wife always says that........

 

[s sidewall]

Don't you hate when that happens.

Steve Sidwell, Samsung On5 using Tapatalk

 

[heimannm]

There is a flimsy check valve in the MDC, like a piece of diaphragm in a brass body. If it was setting too long with fuel the check valve may have gotten gummed up.

Make sure to pressure test the carburetor when you have it out again to make sure the needle and seat are functioning properly as well.

Mark

 

[Deegore]

Thanks for the help.
I put 10psi to the carb and it is slowly losing pressure. Put it in water and the bubbles are coming from a small hole next to the venturi on the side that bolts to the engine.
I think this hole provides pressure from the crankcase to the fuel pump. Maybe a bad fuel pump diaphragm?
I put it together and it runs ok but I have to back the low screw out way past best idle to keep it from bogging down when I pull the trigger. Still doest want to start when its warm.

 

[heimannm]

Certainly acts like a bad fuel pump diaphragm, there should not be any leakage at that point.

L screw adjusted further open than normal suggests you may still have a partially plugged passageway in the carburetor. Remove the L screw completely and try shooting some carburetor cleaner through, let it soak for a bit, repeat until you get a nice clear stream coming out of the opening in the venture.

Mark

 

[lone wolf]

Thanks for the help.
I put 10psi to the carb and it is slowly losing pressure. Put it in water and the bubbles are coming from a small hole next to the venturi on the side that bolts to the engine.
I think this hole provides pressure from the crankcase to the fuel pump. Maybe a bad fuel pump diaphragm?
I put it together and it runs ok but I have to back the low screw out way past best idle to keep it from bogging down when I pull the trigger. Still doest want to start when its warm.

I can say many of my problems with all my equipment is always a damn carb! I hate Ethanol!

 

[Deegore]

Thanks Mark, I followed your advice and that helped me to find the cause of my problems. There is a nice big Crack inside the venturi. Replacement carb on the way.

Unrelated: it looks like some of these saws came with a chain brake. Mine doesn't have one. If I buy one will it fit?

 

[heimannm]

The clutch cover with a brake should be a bolt on replacement for what you have currently.



Bad photo but the only one I have with the brake on a short clutch cover



Later models had a longer clutch cover that also enclosed the muffler. This should also be a bolt on replacement if you don't mind the added weight & bulk.



Mark