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Looking for help reguarding a old saw my father in law used in the late 70s.He passed away last year and my mother in law wants me to get it running.
The saw is a McCulloch pro mac 510 and not many parts are available.
Started out rebuilding the zama c1 carburetor,replacing the fuel lines and adding a bulb type primer. Got the saw running and after a few seconds it would lose all spark and die.Coil tested bad so i replaced it with a used one as they are no longer available.Replaced the points and condenser with the oregon ignition module.Saw starts and runs but when running at a constant speed it will begin to rev then die. Any help woud be appreciated.Thanks

Sounds like its (carb) either out of adjustment or its sucking air.

Ive tried settings from 1 turn out on both needles to 2 turns out.This saw doesnt have a vented fuel tank.Could a leak in the tank cause this?

OK,Repared crack in tank.Replaced intake and carb gasket and still no change.It will start,run a few seconds,rev then die.Checked compression and it has 82 psi and 85 with oil in the chamber.
What is the problem with this thing?

Just a thought is the fuel lines swapped to the wrong spot?

Tried that too.push the primer in and it would stay sucked it.
Relized last night I was suppose to do the compression check with therotle wide open.I didnt do that.
Latter today I will recheck that.

Re done the compression test and got the same reading 82 psi.

Instaled a new piston and ring.Got a 3 pound increase in compression.
Same result.Its hard to start,runs about 30 seconds.revs and dies.
Where could this be sucking air from?Im at a lost.

There is NO WAY to correctly add a primer on these units without changing the carb. Could you give me a diagram of how you routed it?

I just restored one of these units, and they really don't need a primer - adjust them correctly and they will start in a few pulls.

midnightmaniac said:

Instaled a new piston and ring.Got a 3 pound increase in compression.
Same result.Its hard to start,runs about 30 seconds.revs and dies.
Where could this be sucking air from?Im at a lost.

Click to expand...

Maybe a fuel problem the Mac is not designed for a primer.

There are several areas it could be sucking air. Ran across this article a while back while working on a saw- http://www.madsens1.com/saw_airleak.htm

Tried replacing the crank seals and strill have the same problem.

If you compression readings are correct then the saw has marginal secondary compression.
Have you done a leak down test on it.?
If it was used a lot there could be significant wear in the bore.
You said you replaced the piston & ring but did you measure the bore first ?
Not sure if this one had a blind barrel or not but I have sent back a lot of basket cases because the owners bought all the bits without first measuring things.
More than one had barrels so worn, the ring only touched in 2 or 3 places.
Single ring motors are not meant to be repaired.
You say you replaced the crank seals but did you pressure test them in both compression 5-10 PSI and vacuum 12" ?
You say the tank is not vented, well it has to be vented if air can not get in fuel can not get out .
Some have a vent in the cap while others have a vent in the tank itself and some tanks have a double vent to prevent over pressure.

Have you tried the engine with the kill wire removed from the magneto ?
Have you done an air gap evaluation of the magneto ?
How strong are the magnets in the flywheel ?
They should be strong enough to support the weight of the flywheel hanging from a length of pipe or under a steel shelf.

We have no idea about your mechanical aptitude
People tell us all sorts of things like "I cleaned the carb real good " = sprayed a full can of cleaner through the venturi
or
Replaced the seals - put them in backwards - failed to clean the shat properly sore tore up the lip
etc etc etc

And finally, a primer bulb on a hand held is actually a purge valve, it's job is to suck all of the air out of the carb so the diaphragm chamber is full of fuel.
As such, it sucks from the carb and blows into the tank.
It is not like a mower which really is a primer and floods the engine for starting.
If you have hooked one up to a non primer carb so it is pumping into the carb, it will not work as all you do is compress any air in the system.
Primers have a one way valve in them that prevents back flow and keeps a constant pressure head on the carb.

by any chance do you have an update to how far along you got with this?.......really would like to know

midnightmaniac said:

Looking for help reguarding a old saw my father in law used in the late 70s.He passed away last year and my mother in law wants me to get it running.
The saw is a McCulloch pro mac 510 and not many parts are available.
Started out rebuilding the zama c1 carburetor,replacing the fuel lines and adding a bulb type primer. Got the saw running and after a few seconds it would lose all spark and die.Coil tested bad so i replaced it with a used one as they are no longer available.Replaced the points and condenser with the oregon ignition module.Saw starts and runs but when running at a constant speed it will begin to rev then die. Any help woud be appreciated.Thanks

Click to expand...

Might try here ...... http://www.lilredbarn.net/McCulloch-510-Chainsaw-Parts-s/1605.htm

Check the diaphragm's again it sounds like a fuel problem.....

Slow down fellas, this is a thread ran from OCTOBER 2016 to JUNE 2017.
Last post from the originator June 23 2017.
Russ just wanted to know the outcome, I doubt the OP needs any help as they have either fixed it or given up & tossed it.

exactly