Mac 10-10 spark “fuel” and compression but won’t start.

[MelonBoi1]

I just rebuilt my mac 10-10 and it has sufficient compression to run, it is above 125 psi and spark is good it is bright blue, and when I put fuel down the carbs throat it starts and then dies. The carb is freshly rebuilt (by leons chainsaw parts and repair) and I am sure we can get this situated because already the good news is that it will fire, it just won't stay running. So I put fuel in the tank and it won't start. Check the fuel line for blockage and it flows just fine. In case the carburetor was just dry and needed to be primed I kept trying to put 2 cycle mix down the carburetors throat and that worked but like I said, it won't stay running, I did that a couple more times and then when I did it again it just wouldn't start. I tried unflooding the engine but that didn't help, I will try again tomorrow but I need answers, I have worked so hard on this saw and I want to try everything before just flushing it all down the drain.

[rusticretreater]

See if this video helps you out.
McCulloch MAC 10-10 Automatic Chainsaw: Get Running Again
https://www.youtube.com/watch?v=bzWvGvlW98U

[MelonBoi1]

I don't need a video, I need someone to help me.

[doc henderson]

so, you are not getting fuel via the "carbonator" (carburetor).  It works when dumped in and not when trying to aspirate from the carb.  fuel is the problem.  

[doc henderson]

see if the folks that rebuilt the carb can look at it for you, if you cannot find the prob.  starts at the tank filter all the way to the carb venturi.  I had one that ran for the first half a tank then would die and not restart.  My Stihl mechanic told me a common prob. is a formed fuel line that had a bend, would get a crack and at half a tank, start sucking air.  he fixed it in 10 minutes.

[doc henderson]

I am not familiar with the mac 10.  will it run on choke, or does it have a primer bulb?  I had two Mac saws but that has been over 30 years ago.  one homelite and nothing but Stihl since.

[beenthere]

Sounds like an air leak in a fuel hose, or something on that order (from listening to others talk about this symptom). 

[chet]

I don't need a video, I need someone to help me.

Just by the fact that you had a shop go through the carb, rather than doing it yourself.  I'm guessing, maybe just maybe, you might have found something to help you diagnose the problem with your saw,  watching the video.  Rude responses such as yours above are not needed or tolerated here.

[Old Greenhorn]

[MelonBoi1]

I don't need a video, I need someone to help me.

Just by the fact that you had a shop go through the carb, rather than doing it yourself.  I'm guessing, maybe just maybe, you might have found something to help you diagnose the problem with your saw,  watching the video.  Rude responses such as yours above are not needed or tolerated here.

I am sorry if that came across as rude for that was not my intent, I am just frustrated that I put a lot of effort into this thing just for it not to run. There is no primer on it and I went through the carburetor myself too and all works fine, I checked the line and it is also fine and fuel flowed through it just as it should. Though When I did take the carb apart I did notice that it was bone dry, as if it wasn't getting fuel to it and that basically confirmed that it wasn't getting fuel to the carb to get into the engine. I suspect it is something with the way it sucks the fuel with crankcase pressure. But I am not sure.

[chet]

Not familiar with that saw, But assuming it doesn't have an impulse line. The first thing to then check, is when you installed the carb, is the carb to intake gasket on correctly. There should be a single small hole on one side of the gasket. That hole must line up with the hole in the intake.  If you flipped that gasket you are blocking the crankcase impulse.

[doc henderson]

they can be tricky devils.  If you take it to the shop that did the carb, they might have a look.  they do not want anyone thinking the carb did not work after a rebuild, but they may charge you a fee, if the problem is not the carb.  there are so many factors, but at least we know it is not getting fuel to the combustion chamber and you have a place to start.  this is the most common problem diagnostically in my opinion and there should be a fix, not a wasted toss "it in the can" solution.

[MelonBoi1]

they can be tricky devils.  If you take it to the shop that did the carb, they might have a look.  they do not want anyone thinking the carb did not work after a rebuild, but they may charge you a fee, if the problem is not the carb.  there are so many factors, but at least we know it is not getting fuel to the combustion chamber and you have a place to start.  this is the most common problem diagnostically in my opinion and there should be a fix, not a wasted toss "it in the can" solution.

Just to clarify I did not take it to a specific shop I bought it as a rebuilt carburetor from Leon's chainsaw parts and repair.

[thecfarm]

Just so you know about the you tube help.
My stepson can watch youtube and change motors. I entered his life in his mid 20's. He had a family and I was not much help showing him how to turn wrenches. His Father was not around to show him anything.
Now he can watch youtube and work on his vehicles.

[Al_Smith]

A common problem with the 10 series McCullochs is the fuel line inside the tank develop a small slit in them which will stop them from sucking fuel .Unless that fuel line has been replaced it might be very old and prone to breakage .Try filling the tank clear up to the top if you haven't already .

[DHansen]

Is the needle stuck in the seat from the carb sitting in storage or on the shelf?  Is the pulse circuit clear at the base gasket and to the block?  The pulse circuit is needed for fuel to be pumped, but the needle is a location that stops the flow into the carburetor.  Just two things that I would check if I was working on this 10-10. 

[MelonBoi1]

A common problem with the 10 series McCullochs is the fuel line inside the tank develop a small slit in them which will stop them from sucking fuel .Unless that fuel line has been replaced it might be very old and prone to breakage .Try filling the tank clear up to the top if you haven't already

A common problem with the 10 series McCullochs is the fuel line inside the tank develop a small slit in them which will stop them from sucking fuel .Unless that fuel line has been replaced it might be very old and prone to breakage .Try filling the tank clear up to the top if you haven't already .

The line is new and flexible.

The line is new and flexible

[Hilltop366]

Old saw, If everything else checks out it could be the crank seals.

[MelonBoi1]

Is the needle stuck in the seat from the carb sitting in storage or on the shelf?  Is the pulse circuit clear at the base gasket and to the block?  The pulse circuit is needed for fuel to be pumped, but the needle is a location that stops the flow into the carburetor.  Just two things that I would check if I was working on this 10-10.

I made sure the needle was unstuck, I do plan to do a full inspection on those pulse circuits.

[MelonBoi1]

Old saw, If everything else checks out it could be the crank seals.

The saw is restored by me, new rings piston, seals everything.

[Al_Smith]

As usual attempting to trouble shoot a chainsaw over the internet is like herding cats .One last thing then I'm done .If I am correct the carb has a hole in it for the impuse which comes from the cylinder via a hole in the intake .It should have a  gasket with a hole in it for the impulse and if it's installed bottom side up it will block the impulse .No impulse no putt putt.

[chet]

Al you weren't paying attention, we covered that. 

[DHansen]

You could try this to help with diagnosis.  Get a clear bottle Put 2 stroke fuel in it about half full.  Mark fuel level with a sharpie.  Use a clear hose from the bottle to the carb inlet fitting.  Remove the spark plug.  Have ignition shut off so there is no spark.  Pull the engine over a few times and see if it pulls fuel through the clear hose.  This would determine if the saw is capable of pumping fuel.

[doc henderson]

OK, I misunderstood.  so, are they online?  If it checks out bad, you may want to let them know to see if they can make it up to you.

[lurk]

Didn't see any mention of pressure and vac testing the crankcase after the rebuild, I read the seals were changed but that doesn't mean they're not leaking. Obviously a leak would cause a very weak or non excitant pulse to the fuel pump. 

Also if you used sealant on any of the gaskets make sure it hasn't plugged the pulse channel.   And as mentioned many times, the inlet gaskets and insulator need to be the correct ones and fitted correctly.