McCulloch Chain Saws

[MacAttack]

I guess my points need some attention....thoughts? Source of my weak spark?

 

[vinnywv]

Cleaning them yes. They arent horrible but pitted. Clean them up anf that will help. With electircity in any form....clean everything. All points of contact with every terminal. Clean off where the coil mounts to the engine so you have a good ground. Clean every spot that any electrical part touches anything. Without good clean contacts electricity can weaken. Also maybe think about the condenser. That helps store the spark. It could be a hinderence also. Power chips such as nova II chips or others can help diagnose problems. They take the place of points and condenser. I will often temporarily put one on a saw to test the points and condenser. If i have the hot white spark with a chip and a orange or less white spark without then likely the points or condenser are the culprit. I do have several saws that run with a chip all the time and others i keep the points. But clean every contact and try again.

 

[cbfarmall]

Depending on how the points come apart, I clamp them in a vice and hit them with a chain raker flat file, then polish with ultra fine sandpaper, degrease and wipe with a dollar bill. Both sides.

I found on my S250, which uses the same ignition, they get real touchy if the gap is too wide. And by touchy, I mean they don't spark. Double and triple check the gap after you tighten.

 

[matt_lamb_160]

Check the condenser. The coils on these saws are very reliable and the points are pretty robust.

 

[Rocker59]

I was taught to take a strip of 1000 grit sand paper and fold it over. With the points assembled, put the sand paper between the points and pull it slowly through the points, keeping pressure on assy to keep it closed. This way, if the contacts are not flat to the assy, they are parallel to each other.

 

[MacAttack]

Not perfect....but a LOT better.

 

[MacAttack]

Thanks for all the ideas!

I do have a Fluke meter that measures capacitance, I'm going to try and get a reading on the condenser.

 

[Joe Crow]

I used Mark's method to clean the points and the saw fired right up

 

[MacAttack]

What is a good value for the condenser?

I'm showing about 274 nF of capacitance.

I think that's about .274 Microfarads. My shop manual says .18 to .22 is in-spec. I don't know if .274 is better or worse than that....

 

[Jeffrey F.]

This saw is just filthy.... I got the phenolic disc and pump shaft out of the oil pump, I have PB blaster soaking it. I'm crossing my fingers that it works, especially if it has one of those tiny check balls like in a Mini Mac.
I will also need to clean up the bore for the disc and hopefully get it moving smoothly again.

Slow and steady on this rebuild....

View attachment 1212471View attachment 1212472

If you need any gaskets or diaphragms made let me know.

 

[MacAttack]

If you need any gaskets or diaphragms made let me know.

Thanks Jeff!

I'll let you know if I end up needing anything made. I think once I get a good spark the saw will run.

 

[Jeffrey F.]

Not perfect....but a LOT better.

View attachment 1219546View attachment 1219547

My Dad always told me to use Moms emory nail file. But don't get caught .

 

[MacAttack]

Our meters have a pretty hard time distinguishing between 0.5 and 1.0 Ω ... I don't think that would be a problem in your case.

I would check the points again, and clean them with some fine emery or crocus cloth followed by several swipes with clean paper.

Also confirm your point gap is around 0.018".

Mark

The points were pretty pitted and a layer of oxide on them, I now have them like a mirror finish.

The condenser checks out at .270 microfarads of capacitance and when i test it for resistance it climbs to infinity.

I'm hoping to put the saw back together and try it again tonight and see if it runs.

 

[vinnywv]

Yes the points look much better.

 

[MacAttack]

Well fellas....the 450 lives!

It doesn't just run, it runs spectacularly.
I can't say with 100% certainty what it was. I cleaned the points and also swapped the condenser, it took some pulls to get primed up but once the Tillotson was primed up, it started and ran amazing. The auto oiler is even pumping oil like crazy.

There was just one casualty in all this...me. It was after 11pm when i finally had my successful run. Let's just say the wife was not pleased. A 90cc McCulloch with a stack muffler is a tad loud.... and I'm in the doghouse. I probably should have known better haha....but i could taste victory!

Thanks to everyone for all the advice, and a special thanks to Mark and Jeff for supplying parts.