McCulloch Pro Mac 55 woes

[volvoguy]

Hi all,

I just finished putting my pro mac 55 back together (rebuilt carb, resealing leaky gas tank, new gas line, etc) and I can't seem to get it to idle at all. It will pop when choked, and will start and run if I give it lots of throttle, but will die as soon as I let off and it winds down. I have tuned the carb as per service manual instructions (1 turn out for both h and l), it has a good spark, a clean and properly gapped plug, exhaust is not clogged up, just seems to not want to idle. Any suggestions anyone can provide would be great, I am sure I am missing something stupid and its driving me nuts. Thanks in advance for any help.

 

[cus_deluxe]

Tried just giving it a little more L screw? Could be something in the carb still isnt right too. Not familiar with this saw, can u pull off fuel line after you have it running and it dies? Fuel should spill out a little bit if its pulling fuel properly.

 

[smokey7]

Is the crab properly assembled diaphragms and gasket in right order? Metering lever properly setup? Choke staying shut?

 

[volvoguy]

I assembled the carb according to the service manual, metering lever was set as per manual too. Wondering if my gas cap seal is gone and its bleeding air. Seems to be getting gas though. I am pretty stumped, wondering if my timing is off or my oil seals are gone.

 

[Wood Doctor]

Usually if the engine fails to idle down even when the idle is set all the way up, you have low compression. Eventually it won't even start. Hold the saw up with the starter handle. If it drops by itself, the compression is probably gone. It's not a proof positive test, but it works with most of the saws that I own.

I have a Stihl 025 that has lots of compression and a good spark, but it refuses to pop regardless of what carb I install on it. And, all the carbs will make the plug wet with fuel.

 

[volvoguy]

It has ok compression, 115-125 pounds, and that's probably a bit low since my compression tester has a longer hose.

 

[heimannm]

Make sure the gasket under the carburetor is properly positioned.

Mark

 

[TLL]

I am pretty sure the 55 has points and condenser type ignition. You would have to pull off the flywheel to inspect them, but any saw that old (1965?) must have the points cleaned and reset.
TL

 

[heimannm]

PM55 is mid 70's vintage with points. If it pops and runs with WOT then it has spark. It is possible the spark is weak and won't fire at lower speeds but that is a more remote possibility.

Mark