McCullough super pro 81

[bobdag]

bobdag, I know less than most of the Macmen but I have experienced new plugs that will spark in open air but apparently don't under compression. I would try another plug. If you get the same results then your timing may be off. Or you don't have the priming down to the science. There has been many times I couldn't get a pop and I could not tell if I flooded it or didn't give it enough fuel. Usually before I fling the saw across the yard, I just do something else for a while and then come back and try again - most times that solves the too much too little fuel dilemma. Ron

This is a saw a buddy of mine has had for years. He told me to hang it in my shop if it wouldn't work. He bought a new ms362 and is happy. I just thought I'd play with it.

 

[rwoods]

Get it going and you should enjoy running it. They are fine saws. Ron

 

[bobdag]

Get it going and you should enjoy running it. They are fine saws. Ron

So I've heard. I've tried 3 plugs so far with the same outcome. The third plug was out of my 290.

 

[Marshy]

Buckin' Billy Ray used a Super Pro 81 on this massive cedar.


Skip to 4:00 for the cutting.

 

[46 Poulan]

If you put enough fuel straight down the carburetor or through the plug hole it should at least pop even with a torn boot, don't do it too much since it will run out of fuel and run lean at the end of every trial.

Mark

Good point I never thought about Mark-Thanks---David

 

[Kensie1988]

Have you put eyes on the piston yet? Too much compression can also be a bad thing, and 150psi with no carburetor sounds kinda high considering the air can bleed out the intake.

 

[Kensie1988]

And if the flywheel key has sheared you should still at least get a pop, but then you would get a huge kick back from the pull Handle, that’s what happened when mine sheared.

 

[Kensie1988]

Sorry for blowing up your thread but I’m just sitting here posting as I brainstorm, if you have a weak coil you can diagnose that by closing the gap on your spark plug and if it fires off that means your coil is too weak to jump the designated plug gap

 

[heimannm]

The switches on McCulloch saws can be tricky at times, often there is a spot that works but if you slide it further the contact breaks again and it keeps going.

Mark

 

[bobdag]

Sorry for blowing up your thread but I’m just sitting here posting as I brainstorm, if you have a weak coil you can diagnose that by closing the gap on your spark plug and if it fires off that means your coil is too weak to jump the designated plug gap

Don't worry about it. I appreciate all input I can get!

 

[bobdag]

Have you put eyes on the piston yet? Too much compression can also be a bad thing, and 150psi with no carburetor sounds kinda high considering the air can bleed out the intake.

I looked through the intake and noticed some scoring on the cylinder. The piston looked fine on the intake side.

 

[Kensie1988]

Was the scoring on the skirt? If it is that means something may have gotten loose in the bottom end, that happened to my Pro Mac 700, now you will need to pull the muffler to look at the exhaust side to see the cylinder walls, when I looked at mine it looked like the needles bearings came loose and scored they cylinder, same exact symptoms as yours except for mine had low compression, but it was on the low side before it ate the needle bearings.

 

[bobdag]

Was the scoring on the skirt? If it is that means something may have gotten loose in the bottom end, that happened to my Pro Mac 700, now you will need to pull the muffler to look at the exhaust side to see the cylinder walls, when I looked at mine it looked like the needles bearings came loose and scored they cylinder, same exact symptoms as yours except for mine had low compression, but it was on the low side before it ate the needle bearings.

No scoring on the piston on the intake side.

 

[rwoods]

Take the muffler off for a look see. I don't know the effect of no carb, but 150 psi is not remarkable for a SP81. Good repair would be 175 psi and up cold.

Ron

 

[happysaws]

Have you put eyes on the piston yet? Too much compression can also be a bad thing, and 150psi with no carburetor sounds kinda high considering the air can bleed out the intake.

Why would removing the carb reduce compression?

Everything in the engine is the same, whether there's a carb installed or not...

 

[bobdag]

Why would removing the carb reduce compression?

Everything in the engine is the same, whether there's a carb installed or not...

I've always heard to do your comp test with the saw wide open.

 

[rwoods]

I don't have a clue. Any effect of the impulse being open?

Ron

 

[happysaws]

I've always heard to do your comp test with the saw wide open.

I've tried it both ways on the same saw, made no difference.

 

[Kensie1988]

I’ve had a Saw on the bench before testing for compression with and without the carb, and the compression dropped, it was my Dayton 2z463, but it was when I first started working on chainsaws and didn’t really know what I was doing and I don’t use a compression tester much anymore, so it’s not something I’ve really ever thought about hard, and in the back of my head maybe I was thinking of pressure vac testing, who knows, Work has my brain like jelly.

 

[LonestarStihl]

I've tried it both ways on the same saw, made no difference.

Another for it doesn’t matter. I’ve trie both and I’ve tried switching to one or the other after using the opposite. Never changes it