MCCULLOCH The official McCulloch thread

[Lee H]

Double check your points. They must be cleaner than clean. I don't think I
have ever seen a bad Mac condenser or coil.

 

[PogoInTheWoods]

I don't have many Macs, but the first one I rebuilt (SP81) had a bad condenser. From all my reading on the subject I'd say the condenser is the weak link in most points systems and the most likely component to flat out fail. Also easiest and cheapest to replace if only for testing purposes. And even dirty points should make spark..., not necessarily very good spark, but at least something.

 

[heimannm]

If you put dielectric grease on the points, you will have to cleans them very thoroughly, dielectric grease is an insulator (non-conductive is the whole point) so it will prevent the current from flowing as intended.

I like to use some carburetor cleaner to make sure all of the grease, oil, wax, etc. are completely removed.

Mark

 

[Al Smith]

Another little tip on points,on anything is to use a piece of paper,lens cloth after you burnish them .All it takes is a little residue of sand grit to prevent them from working .
I too have never seen a bad points type McCulloch coil and only one solid state coil go bad .

 

[Steve]

You can also eliminate the condenser for testing purposes. Don't go cut wood without it or your coil and points won't last long. Also make sure your points are actually closed. My CP-70 had no spark like your situation and found that when timed by the flywheel the gap was just too big and they looked closed but the connection was not good enough for coil saturation. Lessened the gap .002" and had the bright blue McCulloch spark!

 

[Steve]

Al, I too have only seen one bad electronic coil. On my pm850 it would start and idle but cut out bad above 5000. I guess the transistor was being feed a 2 instead of a one or zero!

 

[Al Smith]

If I'm not mistaken the 850 might use the same coil as the PM 610 .The 610 was the one I bought with a bad coil 25 bucks later it ran like a charm .By the looks of it I doubt it had more than half dozen tanks of fuel through it ,one of the nicest ones I'd ever seen .It's in my shed being stored for my son who now lives in Louisville and has no use for it at the present time .

 

[Al Smith]

Every so often somebody mentions repairs on solid state coils .Problem being a self contained unit is encapsulated ,you can't get into it .
With a separate trigger not a big deal just use another trigger device .Any more they are inexpensive and small .
The trigger itself is relatively simple if you understand electronics being a darlington type transistor gating an SCR using a capacitor ..I'd imagine the RPM limited kind use a zener diode to crow bar the circuit at some predetermined voltage level which be related to RPM's .
Heat is what damages most solid state circuitry .Anything to prevent that keeps them working .

 

[usmcbuckwild]

If you put dielectric grease on the points, you will have to cleans them very thoroughly, dielectric grease is an insulator (non-conductive is the whole point) so it will prevent the current from flowing as intended.

I like to use some carburetor cleaner to make sure all of the grease, oil, wax, etc. are completely removed.

Mark

Absolutely NOT! No grease on the points at all and ensured the crank wipe was not over saturated.

 

[usmcbuckwild]

Every so often somebody mentions repairs on solid state coils .Problem being a self contained unit is encapsulated ,you can't get into it .
With a separate trigger not a big deal just use another trigger device .Any more they are inexpensive and small .
The trigger itself is relatively simple if you understand electronics being a darlington type transistor gating an SCR using a capacitor ..I'd imagine the RPM limited kind use a zener diode to crow bar the circuit at some predetermined voltage level which be related to RPM's .
Heat is what damages most solid state circuitry .Anything to prevent that keeps them working .

I understood all the way up to RPM...

 

[Ikeholt]

I guess I'm more of a bottom feeder on old saws than many of you. The junk I get rarely has a good coil. Many of the old yellowish Mac coils have visible cracks. I've read threads about drying them out and getting them going with an impact wrench, but that doesn' always work.

 

[Steve]

I guess I'm more of a bottom feeder on old saws than many of you. The junk I get rarely has a good coil. Many of the old yellowish Mac coils have visible cracks. I've read threads about drying them out and getting them going with an impact wrench, but that doesn' always work.

Getting them going with an impact wrench???

 

[heimannm]

My brother alerted me to a brick and mortar auction site that is located near him. I "won" a couple of auctions this week.





Not cheap, but I should be able to move some of these along.

Mark

 

[joeymt33]

If I'm not mistaken the 850 might use the same coil as the PM 610 .The 610 was the one I bought with a bad coil 25 bucks later it ran like a charm .By the looks of it I doubt it had more than half dozen tanks of fuel through it ,one of the nicest ones I'd ever seen .It's in my shed being stored for my son who now lives in Louisville and has no use for it at the present time .

They do use the same coil but the 610 wire is longer and can be cut down.

 

[Al Smith]

I understood all the way up to RPM...

The voltage generated by the low voltage side of the coil circuit will increase depending on the speed it turns up to the point of "coil saturation" or max amount it's capable of . It's my understanding at some point a certain voltage will be reached that equates to the given speed it is turning .If the designed circuitry recognizes that it can cut the spark out above that speed acting like a governor .Chop saws and some chainsaws use speed sensing ignitions .One method to do it could be using a Zener diode AKA as a break down diode .At a predetermined voltage the diode becomes in effect a short circuit .What that voltage would be or how to determine that is entirely above my knowledge .

 

[Sleeper]

My brother alerted me to a brick and mortar auction site that is located near him. I "won" a couple of auctions this week.

View attachment 108826

View attachment 108827

Not cheap, but I should be able to move some of these along.

Mark

Is that a PM700? Or SP70? (in the first picture, front)

 

[Ikeholt]

Getting them going with an impact wrench???

Sometimes a saw that has been sitting for years won't have spark when you pull the rope. But if you turn the motor (with the plug out) with a drill or impact wrench it can kind of "wake up" the coil. Not my invention, but I have seen it happen. Your mileage many vary.

 

[Al Smith]

My dad bought a Husky walk behind garden tractor when I was 3 years old .Later in life it might sit a few years between being used .It did not have a recoil type starter .He would belt up another engine from a reel type lawn mower with sliced loop of rope and wind that thing up .It never failed to start .I'm not so certain he ever even changed the oil in it ,looked like creosote.He just added a little if it needed some .Smoked a little is all . I have that thing now since he passed on .It's not stuck and I'll make a bet that even nearly 70 years it will still run .

 

[Steve]

My dad bought a Husky walk behind garden tractor when I was 3 years old .Later in life it might sit a few years between being used .It did not have a recoil type starter .He would belt up another engine from a reel type lawn mower with sliced loop of rope and wind that thing up .It never failed to start .I'm not so certain he ever even changed the oil in it ,looked like creosote.He just added a little if it needed some .Smoked a little is all . I have that thing now since he passed on .It's not stuck and I'll make a bet that even nearly 70 years it will still run .

A Bolens Huski walk behind?

 

[Al Smith]

I don't know if it was or not .Painted green.either Husky or Huskey .It was smaller than the old David -Bradley that used automotive sized tires .2.5-3 HP Briggs engine 6 to 1 reduction . Evidently that winding it up to about running speed woke up the mag so to speak . After that first start up it would light right off from the rope .
The problem with winding up a chainsaw engine with a drill motor is you are trying to unscrew the flywheel nut .I know what happens,the nut comes off ,the flywheel orbits your garage about three times as you run for your life .--Just missed my wifes Cadillac .That would have been very bad .