McCulloch 740/Mc70 revival

[Yukon Stihl]

Hi All
A couple of years ago i picked this saw from an old logger that was semi local to me growing up.I remember him coming into our highway lodge when he was driving some of his trucks.Leo Smith was his name and company went by Leo Smith Logging from Haines Alaska.He was in his eighty's when i got some saws from him.He told me he quite using the saw when he couldn't start it anymore,it was one of his toys,and the last one he sold.I was going to get it running and take it back so he could cut some wood again with it.He was killed last winter by his skidder running over him.At the time he was still using a 046 and an 036 to block up wood and sell it on the honer system from his porch.

 

[Yukon Stihl]

My plan was to give it a good cleaning on the outside and make sure it was tuned and use it as a sleeper saw,there is only one person around here that would know what it was,Gypo Logger lives just down the road from me.
I got it apart and outside cleaned up,then started to make a couple of gaskets and clean the intake area of the block when i saw something that made me look a little deeper and i realized that there was some corrosion inside the saw.
The corrosion is limited to the engine pan and the points/bearing plate on the side,thank god for that because the Mc70 block is untouched and looks like very little run time on it.Can still read the part number on the piston.Yea

 

[Yukon Stihl]

So now that i have it torn down this far i am going to replace the seals and bearings,i think they could be cleaned up but this is more than just a firewood saw,this one will stay here for a while.
So i need a little help,if anyone has bearing and seal numbers i can start the search for parts.Also looking for an engine pan,bearing retainer plate,gasket kit and carb recommendation.I did clean up the bearing plate but it still has corrosion in the deep pits.I am worried that the corrosion will start again.My thoughts are that the old parts that were from the original saw probably had corrosion on them when they were used,and after the saw wasn't used for a number of years the corrosion started to grow again.If anyone has a way to stop it i am all ears.The pan is to far gone to think about using.I scraped about a tablespoon of gritty stuff off it,and i believe some of that gunk is in the bearings.
I have the number off of one bearing,it was made in Canada so it must be old.

 

[heimannm]

Bearing and seals are standard issue so just take the parts to a reliable bearing supply outfit and they can match you up with new ones.

Mark

 

[Al Smith]

You could probably do about as well on prices at this place .https://randysengine.repair/

 

[Al Smith]

As far as that corrosion issue it's probably galvanic reaction more often attributed by being stored on a concrete floor .Happens quite often on old saws .
They make a "fogging oil " used at marinas for storage of outboard boat motors .I've never used it myself but something that might be of interest .

 

[Al Smith]

Now that "pan" deal I assume is the stuffer ? If It were I I wouldn't worry about it .Gaskets,if they aren't torn to shreds clean them up and use a little Permatex number 2 .You'll never know the difference .
That one ,although I didn't look at the IPL should have a piston pump for the bar oiler .Not a bad idea to replace the O ring since it's easy to get too .I didn't once on a 650 gear drive only to later have too .Live and learn .

 

[Al Smith]

Another thing while I'm on a roll .Those old style flat air filters were not the best method to filter out dust etc before the engine injested it but that's about the best they had for the time period .Hard to say the amount that old engine ate .They are pretty tough and it doesn't seem to hurt them .
So ,again just clean the crude off as best you can .Odds are you'll never run that thing long enough to ever wear it out .It might be around another 50 years .

 

[Lee H]

As Mark stated, Bearings and seals can be had at a local bearing supplier.
Gaskets are all over ebay. The gaskets fit many models other than 740 or MC70
so you will have to go by the pic's or part numbers. Ebay seller gotfishon43 is
reproducing many of the Mcculloch gaskets.

 

[Yukon Stihl]

Thanks All for the comments
The "pan"which is the stuffer...
I would like to replace it,there are a couple of deep pits in it that if the corrosion starts again wouldn't take long to get to the oil tank.
Seeing there wasn't any corrosion on the block i think the parts must of had corrosion on them from the original engine.The rest of the saw has the signs of a hard life.I think that when he built this saw it was a toy for playing and racing in the state fair,but being self employed back then the budget was limited.So a dead saw from the junk pile was the base for the Mc70 block.He lived right on the coast so corrosion was a constant companion.
I was told that the flatback carbs had issues.
I also read that the 090 carb has been used on these.
I had cut a couple of gaskets as i was getting ready to reassemble,before i found the rot.
The flywheel has been lightened,by hacksaw.I am going to smooth it up a bit on my lathe.

 

[Al Smith]

The only reason they hacksawed the fins was to get it to wind up faster .On a kart engine and an oval track they wanted them to reach about max RPM's just prior to slowing to drift for the turn .Sprint cars are set up the same way .Kart engines were set up.port wise with what the race conditions might be and the gearing .You had short dirt track,long county fair horse tracks,road courses etc .The karts would actually outrun the midget racers back in the day .Hard to believe a souped up McCulloch outrunning a souped up Ford 60 V8 flathead or Offenhauser 143 --Memories --
You either love a flatback or hate them .I'm in the later club .A good functioning one runs great but getting one there has never been my strong suite .A Tillotson model HL might be a better choice .

 

[Al Smith]

Forgot to add that fellow at Sugar creek supply I hear is making the kits to rebuild a flat back if you want to go that route . Other than that they are rare as a hens tooth .

 

[Lee H]

The block is aluminum and doesn't corrode like magnesium. The stuffer still
might be usable. If you have access to a bead blaster you can see how deep the
corrosion is. You can also add some JB weld to the stuffer on the oil tank side.

 

[Al Smith]

A thought just occurred to me .If that kart engine was used on a kart it probably inhaled a dump truck full of dirt .Most of them had no air filters back in the day .Then too if it was raced on a kart they used heavier oil mix,often castor oil .None of this super duper 50 to 1 stuff .Chances were it was a gasser not a fuely .Some of that crude in the engine might just be cooked earth .If so those were pretty tough engines all things considered .

 

[Chainsaw Jim]

These kits are available, but the metering side is flatter and doesn't have the travel distance the oem ones do. I raised the metering lever a tad bit higher to compensate and had very good results.

 

[Lee H]

Jim, Are you saying the diaphragm is a tad tight like a drum
and doesn't have quite the flex like the oem's.
I believe these kits are made by Joe Salva from Sugar creek supply.

 

[MS290man]

Is it the same as a Mac 10?

 

[Lee H]

From the pic it looks like it should be the same as a MC70 but a MC10 should
have the long finger stuffer do to the shorter stroke they have. Yours is the short
finger which is used in the long stroke motors like the MC70, 75, 100 and 101
as well as the saw motors 797 and SP125's.

 

[MS290man]

It was used on this motor. It’s a kart motor my dad and older brother ran in the mid 60’s.

 

[MS290man]