Mac 120 update

[Diesel JD]

Thanks to you guys who told me how to test for spark, I observed that my little mac does have spark enough to jump the sparkplug gap with a strong blue flame. I still can't get the saw started...here are the problems...
1) Can't get the sparkplug out to check and see if it is fouled...for my test I pulled the boot and used another Mac sparkplug from my 3200.
2) The clutch turns everytime the engine is turned over...when I had the bar and chain on the result was teh chain moving while cranking
3) The saw will not even try to fire...since it has good spark and compression, I assume the carb must be fouled, the spark plug must be junked up, the fuel line is junked up...or the clutch turning at every revolution is robbing some of the power needed for the engine to spin fast enough to start. I'm open to nay and all help. I know this saw isn't the latest and greatest but it has a lot of sentimental value. It was my grandfather's and he was the guy who first introduced me to saws. I'd love to get it running again. Yeah and I know some of you all are real fans of the old Macs so I would appreciate any and all help.
J.D.
P.S. the clutch from my 3200 seems to exactly match the one from the 120...are they interchangeable? Thanks,

 

[ozflea]

Thanks to you guys who told me how to test for spark, I observed that my little mac does have spark enough to jump the sparkplug gap with a strong blue flame. I still can't get the saw started...here are the problems...
1) Can't get the sparkplug out to check and see if it is fouled...for my test I pulled the boot and used another Mac sparkplug from my 3200.

You need a thin walled tube spanner to get it out.

2) The clutch turns everytime the engine is turned over...when I had the bar and chain on the result was teh chain moving while cranking

Sounds as if the clutch has had it


3) The saw will not even try to fire...since it has good spark and compression, I assume the carb must be fouled, the spark plug must be junked up, the fuel line is junked up...or the clutch turning at every revolution is robbing some of the power needed for the engine to spin fast enough to start.

With the clutch dragging i'd say you won't get it to start.

I'm open to nay and all help. I know this saw isn't the latest and greatest but it has a lot of sentimental value. It was my grandfather's and he was the guy who first introduced me to saws. I'd love to get it running again. Yeah and I know some of you all are real fans of the old Macs so I would appreciate any and all help.
J.D.
P.S. the clutch from my 3200 seems to exactly match the one from the 120...are they interchangeable? Thanks,

Yes.

Mc Bob

 

[sawinredneck]

The spanner is a thin walled socket in the states!

First and foremost get the plug out, that will answer most of you're questions right there. If it's all gumed up, if the electrode is missing, test to see if it's getting fuel etc. That is priority number one right now!
Take the cheapest deepwell socket you hve of that size and slowly grind down the outside of it until it fits and get the plug out!

Then listen to everything Bob told you.

 

[RED-85-Z51]

Having worked on a Mac 110, Mac 140, Mac 160s, I can pretty much feel what you are doing right now...

The clutch bearing may be dirty, or bad, take the bar/chain off and take a close look at the clutch. Can you wobble the drum, or move it independently of the driver?
Could be some Debris caught between the shoes and drum as well.

Get the plug out, as has been mentioned, put a new one in, first and foremost.

Then put in fresh fuel, turn the high and low screws IN, then back them out a couple turns each.

Now twist the CHOKE lever, and set your throttle catch. Turn it ON, and give it 10-15 good storng pulls. If the diaphragm in the pump is still good, it might pop off. If NOT, squirt a little fuel in the intake and try that, if yo ucan get it to catch, choke it, and try to let it clean itself out.

If it stil wont start, you are going to have to gut it...not alot of fun.

Start by removing the bar/chain/sidecover.

Then remove the air filter and cover, AND the starter housing.

Next start removing the various screws hidden all over the casing. Get the handles off, then remove the FRONT plate from the case.

You will see the oil tank on the left, and the fuel tank on the right.

You are going to now remove the spark plug, and the stuff around it.

The engine SHOULD, with a little coaxing slide out the front of the case, as long as you have removed ALL the retaining screws and the muffler.

YOu will notice the throttle lever catching as you sldie the engine out. Use a screwdriver to pop it out of ther lever so you dont bend it, or break the throttle lever. Then you may be able to pry off the tanks.

From here you will pretty much have to wing it..the carb is back next ot the coil, likely all covered in gunk..blow the whole assembly off and clean it up. Take the carb off, and rebuild it, cleaning all the little holes out.

This thing is a BEAR to put back together...I hate it!

The hardest part is getting the fuel tank hose ot stay on, while sliding it all back in, THEN putting that little thorttle wire back on...it sometimes takes me 30-45 minutes to get it. Might be an easier way, but I cant find it.

Honestly, if the saw is rough, it might be best to leave it be, if it wont start...these SOB's are fickle as the devil, and re-assembly is terrible.

Ive almost got my 160s done, but it has a bad coil. Got a good coil to put on it, but dreading the task itself.

 

[sawinredneck]

I think that is about the best post I have ever seen you make Red! Good job!

 

[RED-85-Z51]

I think that is about the best post I have ever seen you make Red! Good job!

Thanks.

Good saws when the run, and parts ARE available.

 

[Diesel JD]

The saw is still in great shape. Perhaps I should just switch the clutch over from the 3200, cause I know that one is at least working. Can't say if its the clutch or the drum that really is the problem. Either way I need to get that daggone sparkplug loose in order to replace everything. What if the dreum is shot too, how is it removed? I'm also wondering if I might be missing a critical part in the clutch assy. All that came out and all that I replaced were 1) Clutch 2) Clutch washer 3) Left hand nut. A 5/8" deep socket pulled the plug out of the 3200 with ease, but always slips off the 120. Maybe I need to do as Sawinredneck said, and take my cheapest 5/8" and grind away the sides. Do you all mean to tell me that the saw has to come completely apart almost to refresh the carb? That sucks! This is a great little saw, and all the metal and plastic is perfect, plus as I say it has a sentimental value...and I can attest to whar Red says, that saw is great when running. Grandad took down some huge trees and fed his woodstove with this little saw. Therefore tossing it is not an option and I'd rather not make it a wallhanger. Thanks,
J.D.

 

[Diesel JD]

Okay, using your advice I got the sparkplug out, and now I have even better sprak, but the clutch is still constantly engaged. I thought like you all did that the clutch bearing may be shot. The drum does move independently of trhe clutch. I'm not real familiar with how these inboard mouinted sprockets work, so I'm not exactly sure what I'm looking for. Another thing I was going to ask you all about...the drum and sprocket including the bearing are one unit on my 3200, and the drum just popped off when I undid the clutch, nut and washer on it. Not so on the 120. What else holds it on here? Thanks,
J.D.

 

[RED-85-Z51]

Thats bad if the drum and bearing dont slide off!!!

If you got the nut and clutch shoes/driver off, the drum should slide off the shaft.

If it doesnt slide off, then the roller bearings may have seized, and eaten into the shaft, or melted!

If it is really stubburn, use something to pry it off, or use a 3 jaw puller if you have one, just be careful on the end of the crank.

And yeah, the saw has to come down to the bare engine to do anything, and they COULD have designed it differently. MY 1978 Homelite XL is the same size as the macs, but HOMELITE did it BETTER.

Carb is not piston port intake, it is REED intake, so the carb is on top up front.

There are like 6 screws that hold the starter/sidecover on...the n4 that hold the motor in, 1 holds the muffler on, pop the throttle lever right up top, slide the motor out. I can have one go from running and being used, to a bare engine on my bench in 15 minutes, and bakc together just as fast.

My only complaint with these macs, is they are too loud, and too hard to pull the rope.

 

[Diesel JD]

Just like a 2-cycle outboard then...reed block intake. I'll have to see if that thing will come loose witha little persuasion, I hope it isn't melted to the crank. I know this saw had oiler issues when Granddad had it and after he passed away it was run witha damaged clutch for soem occaisonal work.

 

[RED-85-Z51]

Just like a 2-cycle outboard then...reed block intake. I'll have to see if that thing will come loose witha little persuasion, I hope it isn't melted to the crank. I know this saw had oiler issues when Granddad had it and after he passed away it was run witha damaged clutch for soem occaisonal work.

Now yours has the piston port intake.

Carb is mounted to the side of the jug, as the piston goes up, it creates vacuum in the crankcase, when the piston uncovers the ports on the side of the cylinder, it sucks fuel/oil into the case, and when the piston goes down, presure builds in the case, and at BDC, it blows the fuel/air/oil charge into the cylinder, and as the piston goes back up, it covers the ports and creates compression.

 

[Diesel JD]

Hey thanks for all the help. I have fixed the clutch I think, because now the clutch does not engage when cranking. Also this allowed me to get the engine started. Here are the problems I still have though, the saw doesn't want to idle and also, the chain will not turn once the engine is running and the trigger is engaged. I'm not sure if something is really wrong with the saw or at least the sprocket or if I am just not getting everything lined up quite right. I appreciate your help, any more ideas would be appreciated.

 

[Diesel JD]

Bump. Still need help on the chain issue. I appreciate all the previous replies, things are def. looking up for getting this saw cutting wood again.