McCulloch SE2012s (MAC3200) A/V Conversion

[Chris-PA]

So I did one last mod. Given how the exhaust gases go straight down on this saw I decided to put the screen back in it. There's plenty of area on the screen anyway so it's no performance hit. While I was in there I opened up the one internal baffle and the outlet just a bit:


It felt stronger and I could push it harder than before, but the times through this old ash are not much different. Sorry for the little autumn olive in the way - I didn't see that when I set up the camera.

 

[.404]

Sorry for the little autumn olive in the way -

Would you do it again without the little Autumn Olive in the way.......?

 

[Chris-PA]

Would you do it again without the little Autumn Olive in the way.......?

I'm saving that in case I get an MS180 and need something it can cut.

 

[redfin]

I missed this thread when you first posted Chris. I like your timing schematics.

 

[.404]

I'm saving that in case I get an MS180 and need something it can cut.

You're not qualified for a Stihl. Keep practicing.

 

[Chris-PA]

You're not qualified for a Stihl. Keep practicing.

I have been! I got some Monopoly money and was able to throw that away for nothing, but when it comes to the real stuff I still can't do it.

 

[cali6construction9]

I'm saving that in case I get an MS180 and need something it can cut.

Lol I've dropped about a 3 footer with a ms170 before just alot of back in fourth work

stihl 026 husky 300xp mac 610 efco 132s craftsman 170 mac 1635

 

[Chris-PA]

I was pondering something about smaller displacement engines and decided to open up my spare 38cc McCulloch engine. I found something interesting about these engines (and unrelated to what I was looking for) - they seem to have a bit of a design flaw. The design is clever in the way that they oriented the ports on a horizontal engine so that they could get the carb on the top and the exhaust on the side. However, the result is that the transfers are now located approximately perpendicular to the crank axis, and so they are taking the side thrust of the piston. This would not be an issue if they were closed bottom fed transfers, but it's quad open transfers and there is very little surface area near BDC. The piston has considerable wear in slots on the skirt, while the ring has almost no wear at all (the other side looked similar):



However, the piston from my 32cc did not show that at all. It appears they changed the casting and the 38cc has less surface area for the piston to ride on, especially next to the impulse slot. Here's the 38cc:



And the 32cc:


Not a huge difference, but enough. It looks like on the 38cc they tried to angle the transfers better and taper them for better flow, but there's just not enough cylinder wall at the bottom of the jug. I'm glad I decided to stick with the smaller engine.

 

[bikemike]

I picked up this SE2012s (MAC3200) a few years ago as a lark, because it was cheap and matched my SE3420 McCinderblock:
View attachment 417995
View attachment 417997
It was in great shape and after some fuel line work I found it ran great. It was made in 1994, and I liked the way it was designed. It has a horizontal engine, which is essentially a clamshell, but the bar studs mount to the lower cap (not my picture):
View attachment 417998
I like the way the tab cast into the housing fits into the bar slot:
View attachment 417999
I was impressed enough to do a muffler mod - the baffles got extra holes:
View attachment 418000
There were only two of these holes to start with:
View attachment 418001
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A bunch of extra outlet holes:
View attachment 418003
Then it ran so well I bought a spike for it:
View attachment 417996
With 32cc and a 12" bar it's got plenty of grunt and it's nice and light - but without A/V I never used it. I ran two tanks through it in a row once, and cut a lot of wood too, but my hands were numb for hours.

So I've kept my eyes open for an A/V version of this saw, but they always went for more than I was willing to pay, and I was always involved in other projects. However, I finally got a powerhead for $22 shipped, and all my other saws are working. It's actually a 38cc, and for all I know the engine is fine, but I have plenty of 38-42cc saws and I plan to keep this one at 32cc. Now I just have to wait for it to arrive!

Those also like no baffle and exit hose drill a tat bigger. You want the 36 or 38cc block for that saw

 

[Chris-PA]

You want the 36 or 38cc block for that saw

Not after looking at them - read the last comment I just posted.

 

[bikemike]

Yeah these saws suck so bad you can't give em away

 

[Chris-PA]

Yeah these saws suck so bad you can't give em away

While most think they are junk I disagree, and I like mine a lot now that it has A/V. It but it's a pleasure to use and is light, sturdy, reliable and easy to work on. It does not like to rev (what I was looking in to), even with muffler opened up, a larger carb, and the intake duration increased, but it pulls well.

I would stay away from the 38cc versions based on what I showed above, but I have not looked at the 35cc so I can't say much about them.

 

[bikemike]

While most think they are junk I disagree, and I like mine a lot now that it has A/V. It but it's a pleasure to use and is light, sturdy, reliable and easy to work on. It does not like to rev (what I was looking in to), even with muffler opened up, a larger carb, and the intake duration increased, but it pulls well.

I would stay away from the 38cc versions based on what I showed above, but I have not looked at the 35cc so I can't say much about them.

I admit they are very light and wake up very well to a muff mod. But I still don't like em

 

[Chris-PA]

Yesterday and today I was off of work, and yesterday I spent up in the woods clearing trails and cutting out briers and vines. I used this little saw for all of it, and it ran wonderfully. I had planned to get a video in some actual wood to see if I could get the rpms up, but I never got around to that. It was really nice and light, which was a help as I was climbing a steep hill.

Anyway, while cleaning it I got to thinking about another aspect of this engine that I never really understood - side thrust on the crank. This has little roller bearings and tiny crank, and the side clearance is set by the face of those little bearing races. But there is no positive stop to position the bearings like in my Poulans. Probably there is a spec, but I don't have a manual. I've noticed it had more play than I like.



The 38cc engine I was looking at is a 1995 (one year later than this), and it has these large flat washers added, that sit against the inside edge of the lower cap and set the side to side clearance:



So I tore the whole thing down completely and swapped those washers onto the crank. The side to side play is much reduced, and I'm hoping that will improve longevity. I did try to give it just a tiny bit of spark advance, and I'll have to see if there is any difference.

 

[a. palmer jr.]

I've been working on one of these for quite some time as you know and I finally have it finished and running and oiling well so I'm leaving it alone. I do have another Mac that is A/V but I haven't been able to get it to run right. I've changed the carb and fuel lines, spark plug and it still runs ugly. I'll get back to the a/v saw a little later, maybe change the module and see if that helps but mine certainly wouldn't run as well as Chris's saw does because mine is bone stock.
While working on this I also have been working on a couple of power mac 310 top handle saws, got one of them running but the other one needs a module. Guess I'll try to find a Mini Mac and see if the module from it fits.

 

[Chris-PA]

I love this saw for brush clearing and trail cutting. It's light and runs a decent time on the fuel tank capacity. With the 12" bar and larger nose sprocket it never throws a chain (not enough slop to pull the chain out of the bar groove). I ran quite a few tanks through it again today, and ran great - but I did have to do some repairs to it first.

First, the fuel line I used was just not quite large enough OD to seal well to the tank openings. It worked OK when new but had started leaking, so I had to replace it with 3/16" OD line. More serious though was the A/V spring that broke under the front handle - after 21 years they are no longer available that I could find, and they are smaller than anything else I could find on my other saws. The rear spring from my Poulan 2775 might work, but it's fatter and would hit on the sides. So that meant I had to make one.

I used the chain brake spring from an old Poulan Wild Thing, which was the right diameter and similar wire gauge, but of course much longer. Also, it's a compression spring so the coils are not bound together at rest, which is good. So I had to cut it and use a torch to heat and bend appropriate ends on the spring, which took a couple of tries but I eventually got it right. I'm sure I'll have to make one for the back spring soon.