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McCulloch Mini and Small CC Chainsaw's

MacAttack

MacAttack

I love the smell of 2-stroke
Joined
Nov 15, 2019
Messages
1,256
Location
USA
What adhesive do you guys prefer for holding a sparkplug wire in the coil? The coil had some type of a yellow, brittle epoxy that actually seemed good because it was easy to clean out.
I had a happy surprise while working on Mini Mac engines...the coil that I had assumed was dead on my MM35 engine, had an open circuit on the secondary coil (plug wire to laminations). So for the heck of I pulled the plug wire and tested on the metal spike...and I'll be damned it tested good! Plug wire was faulty. It turns out that metal coil in the plug cap had corrosion on it where it punctured the plug wire and into the core. Cleaned it up and added a little WD40 and now the plug wire has continuity.
 

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MacAttack

MacAttack

I love the smell of 2-stroke
Joined
Nov 15, 2019
Messages
1,256
Location
USA
Thanks Mark! My initial thought was RTV, but wasn't sure if it was the best option.
I'm just a little thrilled that I have another good coil in my arsenal.
I tore into the ultra-clean Mini Mac 30 that I found last year. It's a crying shame something happened that created some radial play in the crank bearings, because this saw looks barely touched. No marks on the hardware inside the housing, it looks like the coil and carb have never been removed. I think someone ran the chain too tight and damaged the bearings. My plan is to swap parts off this engine and onto either the MM35 or the early MM6.
This MM30 has the smaller fuel inlet barb, but the older style recoil. And the recoil is intact!

20210712_222438.jpg
 
MacAttack

MacAttack

I love the smell of 2-stroke
Joined
Nov 15, 2019
Messages
1,256
Location
USA
I keep an eye on Ebay for reasonable deals on bearings and seals but a lot of the time they're used and of uncertain condition. I don't know if there's a better place to look?

I have to look at the bore in the MM30, it's got TONS of static compression when I pull it over. I'm mostly worried the crank could be damaged where it rides in the needle bearings. At this point, I have extra short blocks I could use anyway, and I'll keep an eye out for some NOS bearings.
 
MacAttack

MacAttack

I love the smell of 2-stroke
Joined
Nov 15, 2019
Messages
1,256
Location
USA
I believe I would correct that if you already haven't. That's quite a bit out of adjustment for an engine with such short stroke.
Yes sir, last night I adjusted the points so that a .018" feeler gauge will just slide between them at their max opening.

Also swapping the coil, metering lever in the carb, and a new carb-manifold gasket to see if I can get to run right.
 
heimannm

heimannm

Tree Freak
Joined
Dec 28, 2005
Messages
10,921
Location
Dike, Iowa
I have NOS and new aftermarket bearings and seals for the Mini Mac and Power Mac 6 saws. I think the seals also match the 300 Series saws and the 32/35/38 cc McCulloch saws.

Mark
 
Manic84

Manic84

ArboristSite Guru
Joined
Nov 20, 2019
Messages
630
Location
USA
Well...today was quite eye-opening. I decided to try installing a new check valve without removing the brass retainer.
After about 15 minutes of trying I was about to come back and say that it was impossible and that Manic84 had been jerking our chain...but I kept at it, and I was absolutely able to get a new check valve into place.
It took some patience and careful use of a very small probe, but I was finally able to get the disc into place. I tested the valve with a small piece of tygon fuel line and it worked splendidly. I can blow air into the throttle body but it shuts and doesn't let air into the high speed fuel circuit. I actually used one of my homemade check valves that punched out from a Walbro diaphragm.
Total materials to replace the check valve (not including tools) is a spare diaphragm and one stens welch plug.

New check valve installed and the brass retainer undisturbed:

View attachment 915324

View attachment 915325
View attachment 915326

It's been a while, but I must congratulate you on making and installing your own valve MacAttack, very well done!
I'm betting that after you swap the coil, it'll run like a top.
When you do get it running, let us know. :)
 
MacAttack

MacAttack

I love the smell of 2-stroke
Joined
Nov 15, 2019
Messages
1,256
Location
USA
It's been a while, but I must congratulate you on making and installing your own valve MacAttack, very well done!
I'm betting that after you swap the coil, it'll run like a top.
When you do get it running, let us know. :)
Greetings, and thank you! God-willing with the coil swap the saw will finally come to life.
It was a while for me too, life got busy, I had some "larger" equipment to repair. I finally had a little time to get back to the little Macs.
The check valve idea worked like a charm, thanks to your ideas!
More to come....
 
Manic84

Manic84

ArboristSite Guru
Joined
Nov 20, 2019
Messages
630
Location
USA
I am issuing an admission of how wrong I was and a correction/clarification, as well an apology for my ignorance.
The last thing I want to do is mislead, discourage people or waste their time and money.

Yes, I did use Teflon as a valve, but I had pulled the retainer first, I had not tried bypassing it with the Teflon. While possible with Buna-N, I had ignorantly and naively taken it at face value that it would be possible to do the same with Teflon. It is wildly difficult to do and will fail. You will ruin the Teflon valve, as it is far too stiff. I grossly miscalculated the rigidity of the material, my own ability to manage it and erroneously suggested at one point that it would be possible to correct a mistake with the material... It isn't.

The best material to use for the bypass method is Buna-N. (rubberized diaphragm material)
Teflon, while very resistant to wear and ethanol, will hold it’s shape, (why it’s so good) especially when bent, and that will make it fail as a valve.
If you do want to use the Teflon material as a valve, like the (more expensive) Walbro 86-520 kit, you’ll have to pull the brass retainer, and replace it with the (scarily listed as cheaper) 86-523 kit and just swap the supplied valve out. If not, you must use the Buna-N material for the bypass method. I have not found any method of saving the brass retainer after pulling it. Maybe someday someone will.

What I did was an experiment in durability. And while I am pleased with how it performs, and in it's longevity, as well people's curiosity and desire of wanting to try it for themselves, I must clarify what steps I took and what is needed to make it work. While you can indeed use Teflon as a check valve, it will be impossible to slide it through the opening in the retainer without wrecking it. You will have much better success with using the Buna-N material.

I will admit my ignorant and false assumption, and take full responsibility for not being more thorough. I put the cart before the horse big time here, and I profoundly apologize if I have wasted anyone’s time, and hope this will stop others from doing a frustrating and futile task.
I do believe it is worth doing, just not the way I've suggested.

"Stupid is as stupid does" Once again, I apologize.
 
MacAttack

MacAttack

I love the smell of 2-stroke
Joined
Nov 15, 2019
Messages
1,256
Location
USA
If it makes you feel any better, I made a check valve out of Teflon, I tried to pass it through the brass retainer and after about 15 seconds I said "nope...not going to happen". Haha.
The buna rubber pumper diaphragm material worked perfect though! That plus the hole puncher and feeding it through the retainer was all YOUR ideas so no need to apologize haha. I'm thrilled it works! I could repair 10 mini Mac check valves for the cost of a couple carb diaphragms instead of $110 for Walbro check valve kits!!
I'm hoping I can reassemble my MM25 today with the different coil, adjusted points, new metering lever and new carb to manifold gasket and fingers crossed it will scream.
 
Manic84

Manic84

ArboristSite Guru
Joined
Nov 20, 2019
Messages
630
Location
USA
If it makes you feel any better, I made a check valve out of Teflon, I tried to pass it through the brass retainer and after about 15 seconds I said "nope...not going to happen". Haha.
The buna rubber pumper diaphragm material worked perfect though! That plus the hole puncher and feeding it through the retainer was all YOUR ideas so no need to apologize haha. I'm thrilled it works! I could repair 10 mini Mac check valves for the cost of a couple carb diaphragms instead of $110 for Walbro check valve kits!!
I'm hoping I can reassemble my MM25 today with the different coil, adjusted points, new metering lever and new carb to manifold gasket and fingers crossed it will scream.

I appreciate that and do wish you the best of luck on the Mini Mac 25. (Please let us know how it works)
However, I can’t take all the credit for the method though. To call it exclusively my own would be wrong, and I must give credit where it is due.
I saw it posted on the Mac thread and was completely awestruck by it. It was the member Hoggwood’s idea to use a different kind of modified punch as a more consistent way of making the valves and slipping it through the retainer. Now while people had made valves before, it was always said that someone could just slip it through the retainer, no one really ever saw any clear proof of concept-- enter the creative powerhouse Hoggwood. And while I’m doubting he was the first to do it, I think he was the first to really popularize it as being a viable way to replace the valve.

Now as for my soap boxing about his method, it is because that after having tried it, it does work… Wonderfully. Of course if my tunnel visioned, hack-ass had looked more closely, or tried instead of assuming, I would have realized that the Teflon idea was a no. And that the only possible way to have a Teflon valve is to either pull the seat and swap the 86-523 valve with a homemade one (which I did), or fork over $ 20 for the 86-520 kit.

Although I am glad that I’ve inspired and helped you accomplish something, and saved you quite a bit of time and money in the long run, I’m not the sole person to thank and am undeserving of all the praise.
While I never claimed the method was my own, looking through the thread I realize that was how it reads and was the impression that I left, which was not my intention and I refuse to take all the credit for it.

So, yes I think it is necessary to apologize for the Teflon suggestion and also to clarify what my contributions are here.
 
drumbum

drumbum

ArboristSite Operative
Joined
Nov 11, 2009
Messages
297
Location
nashville
Thanks, this carb has the recessed area and the lever is level down in there. Had the carb apart and no signs anyone had been in there, just stiff diaphragms.
I believe I will give up on this saw. I have been in the carb and swapped some diaphrams around. Could get the saw started and while trying to tune the idle it will eventually die and not restart. Thinking it may have a faulty coil.

Oh the benifits of having multiples in a series for swapping, not spending $40+ for a carb or $? for a coil on a saw that will most likely never get used. Oh well....
 
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