McCulloch Chain Saws

[Jethro 2t sniffer]

The sp70 was auto oiling a little. I've checked the pump and the adjuster wasn't out very far so I've opened it out a heap n see what happens. It does manuel pump a bit too.

never seen a lid cracked before

wound it out

 

[edju1958]

Jethro,something else I thought of - check your oil pick up line to make sure it doesn't have a crack in it,or make sure it's not plugged.(see if you can blow through it).Another thing to cherck is the pulse opening going to the engine,that may be plugged.

If you need more kits just let me know.

 

[edju1958]

The last setting I tried yesterday was 3/4, well it fired up today still set at that - perhaps it needed to dry out after initially being too rich?
There was a bit of smoke coming off the muffler whist pulling it over - unburnt fuel?

View attachment 1094381

Ugh I guess I need to tune it now...

Sounds pretty good.I was going to suggest a new or different spark plug.A fuel system issue & an electronic issue are very close in nature as far as symptoms go & can be difficult to distinguish between the 2.

 

[Jethro 2t sniffer]

Jethro,something else I thought of - check your oil pick up line to make sure it doesn't have a crack in it,or make sure it's not plugged.(see if you can blow through it).Another thing to cherck is the pulse opening going to the engine,that may be plugged.

Good thoughts. I wonder about that 850 losing prime could be the hose

 

[Woodslasher]

Anyone on here have a Super 250 they'd part with? I got a message from the guy who hooked me up with my 125 asking if I could find one for him.

 

[Jethro 2t sniffer]

Sp70 update after a proper run.

It now oils yay but...
Once Hot the tune is all over the place. Crank seals I'd say. Tipping it around changes heaps.

Hopefully not flywheel side as I have pto side seals here. Or 2nd hand flywheel side

Might put fresh carb on 81 n see how it goes

It's annoying right now as I have trees to cut and a baby nocking on the door. Might get a 7-10 out

 

[Squareground3691]

Sp70 update after a proper run.

It now oils yay but...
Once Hot the tune is all over the place. Crank seals I'd say. Tipping it around changes heaps.

Hopefully not flywheel side as I have pto side seals here. Or 2nd hand flywheel side

Might put fresh carb on 81 n see how it goes

It's annoying right now as I have trees to cut and a baby nocking on the door. Might get a 7-10 out

Really like the 7-10 , strong runners

 

[knightmax]

Sp70 update after a proper run.

It now oils yay but...
Once Hot the tune is all over the place. Crank seals I'd say. Tipping it around changes heaps.

Hopefully not flywheel side as I have pto side seals here. Or 2nd hand flywheel side

Might put fresh carb on 81 n see how it goes

It's annoying right now as I have trees to cut and a baby nocking on the door. Might get a 7-10 out

I think you said you already built the carb. Is that crack all the way through the oil tank cover? With the impulse from the crankcase for the oil it could cause an issue though Like You I have never seen one cracked in person to know. otherwise yes I agree you need seals.

 

[Squareground3691]

Anyone on here have a Super 250 they'd part with? I got a message from the guy who hooked me up with my 125 asking if I could find one for him.

https://www.ebay.com/itm/1157163392...lx6FfZ4S9a&var=&widget_ver=artemis&media=COPY

 

[harlanprine]

Can the wise share the use of a vacuum gauge to diagnose? Would it be used to suck out the feul system instead of blowing air? Cause I got one and would love to put it to use for the second time in 20 years.
Trying to resurrect mini mac 30 and 110. Grateful newbie.

 

[Jethro 2t sniffer]

I think you said you already built the carb. Is that crack all the way through the oil tank cover? With the impulse from the crankcase for the oil it could cause an issue though Like You I have never seen one cracked in person to know. otherwise yes I agree you need seals.

The crack isn't leaking oil so hopefully not air. Definitely changes as the crank walks around a little.

Do I try dig out the seal or split it? I don't have flywheel seals or anyway of testing it either except squirting the seal while running.

 

[Maintenance supervisor]

The crack isn't leaking oil so hopefully not air. Definitely changes as the crank walks around a little.

Do I try dig out the seal or split it? I don't have flywheel seals or anyway of testing it either except squirting the seal while running.

Pto side is gonna go in the little bearing cup anyway, I'd try and sneak it in without splitting the case.
Most oil tanks had a hole drilled in the top with some felt and a cotter pin to slow the oil leakage, I wouldn't sweat the crack in the cover.
I'd still spray the seal to see if it kills the saw?

 

[Jethro 2t sniffer]

Pto side is gonna go in the little bearing cup anyway, I'd try and sneak it in without splitting the case.
Most oil tanks had a hole drilled in the top with some felt and a cotter pin to slow the oil leakage, I wouldn't sweat the crack in the cover.
I'd still spray the seal to see if it kills the saw?

I'm not convinced it's seals. I sprayed it at all kinds of angles n no change at all.

What else could be a stray in this carb? What are check valve symptoms? I'll try a known runner carb on after work n see what happens

 

[Jethro 2t sniffer]

No joy. Still running strange. Exactly the same with a good runner 700 carb.

Think it's on the shelf for a tear down and a box of goodies.

Guess it could be any number of things sucking air

 

[vinnywv]

It could be for sure. Impulse line, seals, oil pump seal, manusa oil pump seal, carb sealing, fuel line...lots of places to check. Youll figure it out eventually.

 

[Maintenance supervisor]

I'm not convinced it's seals. I sprayed it at all kinds of angles n no change at all.

What else could be a stray in this carb? What are check valve symptoms? I'll try a known runner carb on after work n see what happens

The check valve is supposed to seal by sucking closed with vacuum after a set point in the throttle position, just after low speed port.
So usually, the saw will idle all day and be fine till the throttle is stabbed then it dies or falls on its face, when the check valve is bad.
A torn or cracked gasket under the intake insulator can lead to all kinds of weirdness also.
Does the tune wander at low idle , or mid/high?

 

[Jethro 2t sniffer]

It could be for sure. Impulse line, seals, oil pump seal, manusa oil pump seal, carb sealing, fuel line...lots of places to check. Youll figure it out eventually.

The joys of old saws

The check valve is supposed to seal by sucking closed with vacuum after a set point in the throttle position, just after low speed port.
So usually, the saw will idle all day and be fine till the throttle is stabbed then it dies or falls on its face, when the check valve is bad.
A torn or cracked gasket under the intake insulator can lead to all kinds of weirdness also.
Does the tune wander at low idle , or mid/high?

Thanks for that description.

When cold it starts n idles happily. Once warm the tune floats around at idle and has got worse. Before it would run mint as then stop after a while and had gone rich but only at idle. On throttle it was fine at any angle. Now it goes lean on throttle when tilted. Gotta be seals

 

[IdahoMac]

This is a start... Ipl and service manual for a 790 and other big saws....

Hey thanks! That service manual should be pretty handy. My 790 has a w-1 welder engine in it, trying to find an airleak at the moment.

 

[Breckinridge Elkins]

Hello folks,
I am hoping for some information about an old saw. On the bottom of the case it has a big "1" next to 51 over 61. I am guessing the 1-51 is the base powerhead and 1-61 is the gear drive conversion? On the other side I see a "1692". Maybe the serial? Would anybody hazard a guess as to when this saw was made? I apologize if the information has already been posted. This thread is 2400 pages and I am slowly chewing through it.
I have been looking at this saw for days trying to figure out the model number. Then I blasted the underside with some brake cleaner to knock the old redwood dust and oil off. Well, don't do that. The old paint doesn't like brake cleaner. It curled right off. But it did reveal the model number.

I am hoping to get this saw running, purely for nostagia reasons. It was my grandpa's saw and he gave it to my dad in the 70's. It ran strong when dad parked it back in 1990 or so and hasn't been started since. Gotta drink some beer and burn some steaks right now but I will post more pictures later.

 

[vinnywv]

Yes its a 1-61 if its gear drive. If its not its a 1-51. Made in 1960 or 1961 according to acresinternet site.