McCulloch SP 125C

[StihlNAlberta]

So my friends i am looking for some guidance. Calling all "MAC" pros.

Finally found time to open up my nice old SP 125. Been a while but it did fire after a tad of priming ... ran for about 2 minutes then she just died.

1. Changed plug
2. Checked compression .... 160. Kill switch wasn't off and throttle was not @ WOT. oops.
3. Fuel Filter ok, lines ok.
4. NO carb rebuild but when it ran for that short time it ran great. Idled, reved up and was responsive.
5. Pulled recoil cover and checked wires, all looked ok.
6. Pulled off kill switch wire from coil and pulled .... no spark

Ordered a coil and changed it out. The coil fit pretty tight against the head/cooling fins but I made a couple grinds with my Dremmel in the one fin and it now fits fine (yeah I know), but will get hot. I have pics but I'd be damned if I know how to upload pics on a computer of my cell phone. I got the recoil back together and gave it a few pulls. Ahh what a nice strong spark!! I can't remember but I think the kill switch cord was still off. Put things back together and got a bit of a work out trying to get it going a day later. Nothing so I pulled the plug and checked for spark again and nothing. All I did was let it sit a couple days in between spark and no spark. The spark was gone even bypassing the kill switch.

Got it down to the coil (which looked like it was not truly round by a few 1000's) and used my homemade flywheel puller which works like dream.

7. Ordered a new condenser
8. Have new points to install
9. Blew out the area and cleaned things up with compressed air. Flywheel looks ok (didn't spin on the crank) and the key and shaft look great.
10. Ordered along with the other goods a new flywheel for $30.00 (I hit the one flywheel key and damaged it a bit when I was trying to remove with a hammer first off before my puller). It prob could be repaired but the flywheel I have is not perfectly round. I'm gonna ask if the is a SP125 specific.

So I am waiting for parts and want to understand the whole "points" thing and how to properly R&R them. How to set up the points properly. Condenser seems pretty strait forward, flywheel? Key will align with the arrow @ TDC? Looks like the key and TDC point directly at the coil.

So this brings to where I am now. Waiting and trying to do some reading on the rest so I complete it properly. I have nothing but time and don't want to get it back together to find I missed something.

Oh yeah, there was a hardened silicone type material around the wire end connectors at the points. Where the coil wire and the condenser wires meet the coil. Little plastic shield, little plastic spacer and that glue. Kinda looked like old ultra copper. What does this stuff do and is it necessary?

Wow, fingers are tired, but any help would be greatly appreciated!!

Cheers.

 

[cpr]

The goo was there to keep moisture out of the points compartment. Not absolutely required to put it back, but a dab of dielectric grease wouldn't hurt anything.

Mac flywheels are universal across the 90- & Super Series karts and saws with one exception. SP125s and various karts had a 5deg. advanced wheel. Otherwise, they all bolt up to one-another. You can see a photo of the difference here: http://www.arboristsite.com/chainsaw/160244-14.htm#post3381239

Put in all the points parts and tighten the mounting screw. Get the adjustment screw lightly seated and then use a straight blade screw driver in the provided slot to adjust the points to open .019-.020 (I usually set them at .019). Keep the screwdriver in the slot when you tighten the adjustment so it can't move.

Re install the flywheel. The key will keep it in time. Install the laminations to .010 from the flywheel and run the saw for a few minutes. After, pop the wheel back off and check the points, they invariably move. Reset to .019 and you ought to be good to go from there.

They're a heck of a good, strong, fun saw to run. Then get a 797 and really feel something.

 

[StihlNAlberta]

Sp 125

Thanks for the great info!! I got the point in and set up as per your specs. Still waiting on the condenser and some other stuff. I will repost when I get her back together!! I think it should run like a top.

 

[leeha]

+1 on cpr's comments.
I would say replace the points and condenser and you
would be good to go. Your original coil is probably good.
I have rebuilt many of these saws and have never replaced
a coil. It's always points and condenser.





Lee

 

[StihlNAlberta]

Sp 125

+1 on cpr's comments.
I would say replace the points and condenser and you
would be good to go. Your original coil is probably good.
I have rebuilt many of these saws and have never replaced
a coil. It's always points and condenser.


Great to know, thanks. It looked a bit odd but the coil mounted in such a fashion that the plug wire hit one of the cooling fins on the jug. I modified the fin a little bit and the new coil works fine but it tight to the head. I was told the coil could be taken apart and "flipped" but I can't see how. Just now waiting on parts. Any idea what compression this saw should be runnin at?

 

[cpr]

The laminations are in the pack via two little clips in the center, one each side of the stack. Get the little ears on those clips pried up with a small screwdriver and the laminations slip out. Reverse to put them back in. I'll get pics in a while.

 

[cpr]

This is an older 700 series coil, but you get the idea.

View attachment 260009
View attachment 260005View attachment 260009
View attachment 260006View attachment 260006View attachment 260006
View attachment 260009

 

[StihlNAlberta]

McCulloch

Here's what I got going on. I'm hoping there are 2 pics attached.

Doesn't quite look the same as your coil.

 

[cpr]

Only thing I'll ad is to use a torque wrench on the 6 bolts that hold the points covers. Those bolts also hold down the inner cover containing the flywheel-side crank bearing. I like to keep that from binding in any way. Second, all of them have spring steel under them with an ear pried up against the bolt to keep it from backing off. Some say that's overkill, but I paid good money for my 7.5s and doing it right doesn't take any longer than it did to read this. You'll waste more time #####in' off in the WTF pic thread than that, HAHA!

 

[cpr]

Here's what I got going on. I'm hoping there are 2 pics attached.

Doesn't quite look the same as your coil.

Oops, my mistake. Forgot how different they were. Been awhile. I do know they press out, but my only 125 is 40 miles away at the old man's right now.

 

[StihlNAlberta]

McCulloch

Well, I'm keeping my fingers crossed that these are the proper components for the 125C. Sometimes used saws get lots of incorrect replacement parts along the way and this is the only one I own and don't have anything to compare. Pretty sure the McCulloch SP105 would have used some of the same components but not sure.

Anyways, thanks again for the pics and info!!

 

[watsonr]

Make sure the coil is making good contact between the saw body and the coil. Pull the plug boot and make sure the plug connector (that medal spring looking thingy) is making good contact with the internal core wire and then unscrew the plug wire from the coil and make sure its screwed into the coil firmly.... making contact with the internal core wire. Sometimes they are just not making a good connection and pulling on the wire, twisting it around to make sure its down on the plug will allow just enough slop to not make contact.

Last resort.... convert it to pointless ignition with an aftermarket module. There about $20 and any small engine shop carries them.

Like Lee said, not may coils go bad.... and I haven't had one yet either. Did you recheck the points gap? And why did you have to modify the fins... you sure its the right coil?

 

[carym2a]

opcorn: everything sounds like she should run, what about the spark plug and wire, Iv seen them ck for continuity and pass, just to find a small brake after more testing.

 

[StihlNAlberta]

SP 125c

Well good point on the coil, I'm not exactly sure if it is correct but it looks like the one that came off it, and it did run nice and crisp prior to me opening up the flywheel. I did install a brand new point and will gap to .019 as recommended earlier in this thread. I ordered an inline tester for spark which should help alleviate the possibility of a bad boot .... However that would be an easy fix!! I'll check that out tomorrow.

This brings me to another question. The shaggy and brittle ground wire on the front of the saw. I took it off and cleaned up all the contacts. Could this be a contributing factor? I see where it has been rubbing on bare metal previously. ??

On a good note, the saw is spotlessly clean and nice to work on.

:msp_thumbup:

 

[heimannm]

The wire at the front is simply to be sure the tank/handle/switch are electrically common to the engine, otherwise the stop switch would not be able to ground out the primary side of the ignition.

Go back to your original points and have a look at the contacts, I expect you will find that they are slightly burned/pitted, or just dirty. Clean them up with some fine emery paper, then clean them again with some carburetor cleaner and compressed air and you will have a work set of spare points.

You can check the condenser with a simple VOM set on the highest ohms scale, connect the leads to the condenser and it should read as an open circuit. Reverse the leads and watch for a slight blip on the meter as the condenser discharges, then reads as an open again. Do this several times and you will likely discover the condenser is O.K. as well.

I'm not sure what's going on with you coil, here is what mine looks like. Sorry for the poor photos, not a very good camera in those days.

Mark

 

[StihlNAlberta]

Sp125c

Well finally back from my time off and had a chance to tackle the MAC 125 parts that came in the mail.

1. New Coil (as per seller)
2. New condenser
3. New plug (Champion DJ8J)

Got everything back together with the new condenser and coil and for the life of me I still can’t get a spark. Contacts are clean (coil, wire ends, point connections), points (.019) are set according to spec. as is the coil (.010), wires are all hooked up correct and I have tried all different scenarios; even bypassing the kill switch again. One thing I have yet to do is check all wires with my ohm meter to see that they have connectivity and are not internally broken or cracked.

No spark.

Funny thing is when I hook up my test light in-between the plug and plug boot, it shows a dim light as if to tell you there is spark. I don’t get it.

From what I gather the new flywheel I installed which is the same as my old except with a bunch more cooling fins, will be kept in time via the crankshaft key and should not need adjusting. I gather this is not an advanced timing flywheel either.

Has anyone any information on getting a coil and electronic ignition for this saw so I could perhaps eliminate the points and condenser? Manufacture and part number(s)? Wondering if this would be the way to go.

Saw has great compression and everything else is tip top, just no spark. I have tried to prime with fuel to at least make sure, but absolutely nothing.

Anyone have any suggestions? Thanks in advance!!

:bang:

 

[leeha]

I have had to clean new points on serveral occasions.
New points can get a coating on them and they won't work.
Try cleaning them with 600 grit wet-dry sand paper. Make
sure you have the white insulating blocks on correctly
where the screw goe's through the points box and attaches
to the wires.
I bought a SP105 from a fellow member here and it didn't
have spark but was suppose to run. He had it all assembled
wrong.




Lee

 

[heimannm]

Everything you need to know about checking the ignition.

Mark

 

[Ambull]

You mentioned that you "bypassed" the kill switch. Normally bypass means to jump out. I think you know not to do this, but you just want to disconnect the kill switch. Often the button and or switch are mounted upside down, so it is very possible to have the switch in the wrong position. With all the big Mac's I have, spark has never been a problem. Getting an Atom chip to replace the points makes things easy, but be aware that they often add some spark advance as well. The saw will run fine, but will fire back sometimes when starting, if you don't pull the recoil fast enough.

You can adjust the position of the throttle in the throttle lock, there is a small flat head screw to adjust. Sometimes getting the right amount of throttle can make starting the saw much easier.

 

[StihlNAlberta]

Sp125c

Awesome info!! I will try cleaning up the points. As for the installation of the wires -> points .... I have it set up as:

Bolt going through the coil wire end and condenser wire end first, clear plastic protector, then white plastic washer up against the outside of the housing and on back side of clear plastic protector, bolt going through coil housing through shiny new points contact to a nut and washer on the inner housing.

Cheers and thank you all. I will get it sorted eventually.

As for bypassing the kill switch, I have just been unplugging the female wire end directly from the coil tab.