McCulloch I-70 rebuild

[Jasonrkba]

I have picked this thing up and started in on it a few times but always got distracted. Today I broke it down. The Piston and cylinder look good. My plans are crank bearings, seals, nuts, bolts ect. I have a few questions to anyone that has worked on these.

Is there an ignition module to delete the points?

I see there are rebuild kits for the carburetor. Is there anything I should be aware of before diving in? I have never messed with this type of carb.

I would like to repaint it. What is the best way to remove paint from magnesium/alloy?

What is the best way to repaint on magnesium/alloy?

Any other suggestions that I should take care of are welcome.

This is a long term project so I'm not in a hurry.

Here is a couple pictures of the tear down.

 

[pioneerguy600]

Just subbing in, I never liked working on the 10 series but my uncle, mothers side of the family loved them.

 

[Jasonrkba]

My uncle, mother's side gave it to me.

 

[pioneerguy600]

When my uncle passed there was close to 50 McCulloch saws left in his workshop, I was told to take them all and clean out the shop, I only kept a Mac15 and a new looking 250, the rest became scrap metal. I never watched closely when he worked on them so only have fleeting memories of what they looked like internally.

 

[Jasonrkba]

That's a lot of saws. Just from what i have done so far there is a lot of bolts that I won't remember where they go. I tore apart a Mac 3200 one time to replace the fuel lines. It was the biggest pita I have worked on to date.

 

[rwoods]

Not to worry - your saw is not of the ten series. Ask your questions in the McCulloch sticky thread and you’ll tap into a lot of knowledge. Ron

 

[Beetlejuice]

Not to worry - your saw is not of the ten series. Ask your questions in the McCulloch sticky thread and you’ll tap into a lot of knowledge. Ron

I can answer a question or two, but there are people on A. S. that know leaps and bounds more than me. They're the pros. I just breed hate and discontent. There is a chip for these motors. I think Google will be your friend on this one...the 1-70 came stock with a Mac carb. BUT, earlier 80cc Macs, and maybe a later one or two came out with either the MAC, or Tillotson H. L., series.. Kits for the Tilly run $17-$25, depending on how pissed off the feller at the parts counter is from blowing dust off the package.. The Mac carb is a little tougher to find.. I need one on my 1-70, but mine has needed it for 33 yrs.. Why rush into these things.. I'll swap mine out one of these days. The MAC wasn't a great carb outta da gate anyway. Lot of the guys are powder coating their saws. Maybe someone will take over the driving now, cuz I am not a painter..so have fun with it. When my kicks it will almost take yer arm off, so I'm a little gun shy. Go thunk

 

[ML12]

I have picked this thing up and started in on it a few times but always got distracted. Today I broke it down. The Piston and cylinder look good. My plans are crank bearings, seals, nuts, bolts ect. I have a few questions to anyone that has worked on these.

Is there an ignition module to delete the points?

I see there are rebuild kits for the carburetor. Is there anything I should be aware of before diving in? I have never messed with this type of carb.

I would like to repaint it. What is the best way to remove paint from magnesium/alloy?

What is the best way to repaint on magnesium/alloy?

There is a chip that can be used to delete the points, but to be honest all of my large frame macs run points ignitions and they all run fantastic. Also all the ignition parts are still available online and Mac shared a ton of parts with other models.

That carburetor is a Tillotson HL. Kits are (should be) available everywhere from $5-$25. They're a pretty simple carb compared to some of the newer cube carburetors. Tillotson's website has the manual for them.

The best way I've found to take paint off and give a nice uniform surface for new paint is to use glass bead in a sand blasting cabinet. Mac paint generally stuck pretty good so it might take a bit of work to get it all off. I've sandblasted lots of saws. just be very very sure to remove all the sand prior to assembly.

Paint is going to be a preference thing. Do you have access to proper spray equipment? Rustoleum sunburst yellow is a pretty good match for mac yellow if you want to go with a spraycan. Most say to use an etching primer on magnesium, but I've not had any problems using engine primer immediately after pulling the parts from the sandblasting cabinet, blowing them off and wiping them down with acetone. The issue is that magnesium oxidizes pretty fast, so if you let the raw parts sit then an etching primer would be better. For clear coat I've had some success using engine paint clear and just letting it dry for a couple weeks before fueling. Others use the 2k (2 part catalyzed) spraycan clear coat from eastwood. Its really up to you.

Good luck. almost all of the parts are still available for these saws. The 1-70 is a removable head 87cc engine, considered by many to be one of the finest engines that Mac made. I have a couple and I can tell you that they pull really hard.

 

[Jasonrkba]

Update. Point of no return.

 

[Beetlejuice]

Update. Point of no return.View attachment 650073 View attachment 650074

You're in it now

 

[Jasonrkba]

So as I was taking apart the saw I noticed the lack of an oil seal on one side. There is some sort of seal in the plate I removed from that side. Can someone explain how this works?

 

[ML12]

There should be an oil seal in the "plate" that you removed. it'll be buried behind the push rod for the points

 

[Jasonrkba]

Got it. Can't believe I missed it. Must have been in hurry. It was a bugger to get out though.

 

[Jasonrkba]

Any chances someone has an exploded diagram to help me reassemble properly? Google wasn't much help for this model.

 

[ML12]

Go to the beg for manuals thread. Its similar to all of the other large frame Mac's of the day.

 

[SS Sniper]

There is a chip that can be used to delete the points, but to be honest all of my large frame macs run points ignitions and they all run fantastic. Also all the ignition parts are still available online and Mac shared a ton of parts with other models.

That carburetor is a Tillotson HL. Kits are (should be) available everywhere from $5-$25. They're a pretty simple carb compared to some of the newer cube carburetors. Tillotson's website has the manual for them.

The best way I've found to take paint off and give a nice uniform surface for new paint is to use glass bead in a sand blasting cabinet. Mac paint generally stuck pretty good so it might take a bit of work to get it all off. I've sandblasted lots of saws. just be very very sure to remove all the sand prior to assembly.

Paint is going to be a preference thing. Do you have access to proper spray equipment? Rustoleum sunburst yellow is a pretty good match for mac yellow if you want to go with a spraycan. Most say to use an etching primer on magnesium, but I've not had any problems using engine primer immediately after pulling the parts from the sandblasting cabinet, blowing them off and wiping them down with acetone. The issue is that magnesium oxidizes pretty fast, so if you let the raw parts sit then an etching primer would be better. For clear coat I've had some success using engine paint clear and just letting it dry for a couple weeks before fueling. Others use the 2k (2 part catalyzed) spraycan clear coat from eastwood. Its really up to you.

Good luck. almost all of the parts are still available for these saws. The 1-70 is a removable head 87cc engine, considered by many to be one of the finest engines that Mac made. I have a couple and I can tell you that they pull really hard.

Good info but I would personally not go through all this only to not use an etching primer. I generally do an etching, sealer, and then SS or 2 part Urethane. I’ve yet to have gas be an issue and the paint is plenty durable and sets up nicely.

I do agree on the oxidization part being a problem, but 10/20 minutes shouldn’t be anything to worry about. Blasting is by far the best prep for these granted you clean them up nicely.

Just make sure your primers/paints are compatible with each other and hit your flash times. A water separator for your compressor is also a must if you choose that route.

Matthew

 

[Jasonrkba]

Lot's of obstacles here. I did a little body work when I was younger but it's been a while. Seems I need a blasting cabinet and have the primer ready to go. I don't have a cabinet but with the limited abilities my shop has my thoughts are as long as all bare metal is sanded clean and the existing painted areas are sanded and well featherd I should be able to hit it with a couple coats of primer than if need be wet sand. Ive started on the tank cover and so far have about 75 percent of the paint removed but the small crevices are going to be tough.

Im also trying to locate an engine gasket kit and that is proving to be difficult. I may have to make my own.

Thanks. Jason.

 

[ray benson]

Any chances someone has an exploded diagram to help me reassemble properly? Google wasn't much help for this model.

Still searching for an ipl for the 1-70, it is #56777, asked a few members. Will let you know.

 

[Jasonrkba]

Thank you!

 

[SS Sniper]

Lot's of obstacles here. I did a little body work when I was younger but it's been a while. Seems I need a blasting cabinet and have the primer ready to go. I don't have a cabinet but with the limited abilities my shop has my thoughts are as long as all bare metal is sanded clean and the existing painted areas are sanded and well featherd I should be able to hit it with a couple coats of primer than if need be wet sand. Ive started on the tank cover and so far have about 75 percent of the paint removed but the small crevices are going to be tough.

Im also trying to locate an engine gasket kit and that is proving to be difficult. I may have to make my own.

Thanks. Jason.

If you soak them in laquer thinner or another solvent it’ll help a lot with the hard to reach areas. Nothing wrong with not having a blast cabinet either; but it’s a big help. I bought one for saws but I find myself using it weekly for anything from people’s tow hitches to engine parts.