MCCULLOCH The official McCulloch thread

[Bigmac]

See "Maverick Spark" on page 2...

… and thanks to Heavy for prodding me to research this a bit further.

Mark

Thanks for posting this Mark! If the points float it causes the same condition as shut off the points with a switch, it could also work like a start retard if you closed the points gap to .012-.014 then flipped the switch to go maverick

 

[Al Smith]

As for Duffy Livingston it was on the site Bob Cromwell had .Bob is no longer among the living .You might be able to "google" Duffy Livingston and find some info . He's gone also,about two years ago .

Now this floating points,"maverick " spark or whatever you call it ,I doubt many would try it .The very idea of a chainsaw engine running at the same speed as a model air plane glow engine isn't a very practical thing to do .At least not to me .If that thing ever came apart it could take your arm off or blind you . Not safe---

 

[Bigmac]

As for Duffy Livingston it was on the site Bob Cromwell had .Bob is no longer among the living .You might be able to "google" Duffy Livingston and find some info . He's gone also,about two years ago .

Now this floating points,"maverick " spark or whatever you call it ,I doubt many would try it .The very idea of a chainsaw engine running at the same speed as a model air plane glow engine isn't a very practical thing to do .At least not to me .If that thing ever came apart it could take your arm off or blind you . Not safe---

Hey Al, maverick spark isn’t that scary, and it’s all up to you how much advance you get, if you have a standard flywheel set at 27 degrees of advance and your points break at 27 degrees that’s your timing, maverick or not, flopping points or not! the factory 5 degree flywheel thrown on the same set up...points still break at the same point 27 degrees, it will not hit 32 degrees until the points stop working or are switched off, this doesn’t mean crazy rpm it’s just a little timing bump. You could also set it up with a tighter point gap and have only 22 degrees initially, and with the standard flywheel with maverick spark it would have 27 degrees, kind of like a start retard. With the 5 degree flywheel it would still got to 32 degrees once maverick, it’s really pretty cool and simple once you think about it! I don’t know if the factory knew the point when points would float, it would be interesting to know! I have heard the the 5 degree flywheel gave a little hotter spark...but it wouldn’t advance the timing unless the points float.

 

[Al Smith]

I have an off set key on one of my Mac 125's .BTW it's 26 degree advance stock not 27 .Not that a degree makes a difference ,just saying .Never the less I agree a little advance improves performance but the idea of 23,000 RPM's sounds a little off the wall .However it does give rise to lively conversation

 

[Bigmac]

Ya 23000 rpm is a lot, more piston speed that formula 1! A Mac 125 has a longer stroke than a formula 1 car! You may already be taking advantage of maverick spark on the offset key 125. If your points don’t float on your offset key 125, your timing won’t advance, the crankshaft Is what the points are set on not the flywheel, so it makes me wonder what rpm 125 points float at? It would be interesting to test with a timing light

 

[Heavy]

A mac 125 in how many rpm is rated 10,000 rpm? is the sp 125 chrome is the most rpm because it has less friction

 

[Al Smith]

The offset key realigns the magnets in the flywheel in relationship to the piston position .This is so even with advanced timing set by the points it's conducting in the highest portion of the sine wave .It's pulsating DC because it only pulsates above the ground potential in a positive amplitude .With this however the timing is still set by the points .In a solid state ignition it's set by a transition of max voltage to dip towards ground potential being more negative ,ever so slightly that is . With a Mac 125 as with other points ignitions they can be adapted to fire from a solid state trigger device if a person wanted to .
For points of debate I doubt seriously if the cylinder is cast iron,chrome plated or hard nickle alloy if it would grossly affect the RPM's at all .Being old school and given a choice mine would be cast iron .It's also the choice of most of the automobile manufactures in the world .Cast iron inside an aluminum alloy block .

 

[Bigmac]

Al, much timing advance are you getting with the points? And at what gap? Are you aligning the magnets to be in the center of the coil when the points break, the edge? How dose one get the sine wave correct?
I really like nikasil for cylinder finish, I am sure Mac would have used it after chrome if they continued production.

 

[Al Smith]

On the 6-10 about 30 degrees .I think it was 25 thou gap .Keep in mind you are limited on how much gap because too much the points don't close .Also much over 30 degrees I've found out makes them hard to start .
On the 125 which has the off set key .It had a solid state trigger that went bad .The points were still there so I reinstalled them .As I recall I didn't open the points up very much so it would not have much over stock advance .I'm guessing maybe 2 more degrees over the standard 26 advance .Starts easy and runs fine which is all I care about .
I might add the way I set the timing on the 6-10 was with a degree wheel and an ohm meter ,static .So it most likely is not exactly 30 degrees .It was a hit and miss type of thing .Once I was satisfied I've never been into that ignition system .Nor I might add have I done anything to the carb .I had that little 6-10 apart so many times it's a wonder I didn't wear out the screws .

 

[Al Smith]

About the sine wave .There isn't anything you can do with it .It's just the pattern the coil makes the magnets pass by it . http://www.foxvalleykart.com/articleindex.html Very interesting articles ,good read

 

[Heavy]

smith you can put a video of your 6-1th turning at 15,000 rpm I would like to hear it

 

[Al Smith]

Yes,just find me the time to do it .Time is one commodity I don't have .

 

[RocketRoss57]

Can anyone help me and my cousin I.D. this saw. All the info I have are these pictures.

 

[RocketRoss57]

He also dropped off 2 super pro 125s for keeps cause he knew I was looking for one. Not to brag at all

 

[Bigmac]

Can anyone help me and my cousin I.D. this saw. All the info I have are these pictures.
View attachment 131855 View attachment 131856 View attachment 131857 View attachment 131858

What is the number on the other side of the block? Probably a 795 or 797, has a decomp the yellow top tank could mean 797 super, the block number will help, 66251 is 797

 

[RocketRoss57]

What is the number on the other side of the block? Probably a 795 or 797, has a decomp the yellow top tank could mean 797 super, the block number will help, 66251 is 797

I didn't notice another number. I'll shoot him a text and see. Thanks

 

[Bigmac]

It has had some replacement part, so it’s hard just looking, the bottom handle looks like it came from a cut off saw, and the muffler looks like a 795, but it dose have a decomp, so 795-797, my 797 has a replacement block, and has 66251 the clutch side bottom of the block but it had the round muffler, some parts may have been replaced so who knows, a bore measurement would tell you too. The 797 supers were all yellow I believe

 

[RocketRoss57]

It has had some replacement part, so it’s hard just looking, the bottom handle looks like it came from a cut off saw, and the muffler looks like a 795, but it dose have a decomp, so 795-797, my 797 has a replacement block, and has 66251 the clutch side bottom of the block but it had the round muffler, some parts may have been replaced so who knows, a bore measurement would tell you too. The 797 supers were all yellow I believe

Yeah the blue on the handle threw me off for sure. Never seen it. On the other hand I haven't seen many big Macs so I don't know. It seems that the handle is painted over with the blue on top of yellow.

 

[Bigmac]

I just pulled this from the internet

 

[RocketRoss57]

Cool. The way this saw was painted made me think that someone did it themselves.