MCCULLOCH The official McCulloch thread

[Al Smith]

I've also got a 10-10S in pristene condition about like that one .

 

[NeSurcaster]

She's sweet man, my P/M 55 is a fantastic cutting saw. She cuts very well for 57cc saw, comparing it to a husky 460 rancher or my dads stihl 036.

 

[heimannm]

Several Italian built saws including more than a few with decent compression. If I am around on a rainy day in the near future I will check a few out.



A few of the saws came from the Oregon company testing where chains were being examined for kick back. Notice how the top handles have been modified for their test rig.



Mark

 

[Steve]

I came home from Oregon with a few more saws that I left home with.

View attachment 129009

Mark

Is that a CP-55 OR 70?

 

[ajschainsaws]

Several Italian built saws including more than a few with decent compression. If I am around on a rainy day in the near future I will check a few out.

View attachment 129168

A few of the saws came from the Oregon company testing where chains were being examined for kick back. Notice how the top handles have been modified for their test rig.

View attachment 129169

Mark

Nice too see that selection of Italian macs they are strong runners especially the pro Mac 61 and 72 but the oil pump failures and lack of replacements is a pain

 

[heimannm]

CP55 is mostly complete, I am sure I have any parts needed short of a new piston; may actually have one of those if it needs it... I already have two CP55 runners, one that I occasionally take to the woods so this one will be available. I also have a CP70 from last year's trip that is available.



Mark

 

[sawmikaze]

Can one of you kind fellows tell me what the pitch/gauge/driver count was on the stock bar on a PM 310 ?

Thank you.

 

[Heavy]

How is it possible that when the points float the rpm increases and the spark continues? Some expert can explain it to me thanks

 

[heimannm]

The points are still opening and closing, it just happens more randomly with the point float/bounce/wildcat. Since this is a single cylinder engine, the contact time is not so critical as it would be on a points ignition for a multi cylinder engine.

Mark

 

[Heavy]

If the points float means that they do not work is that way where I do not understand the question suppose that they stop working at 9,000 rpm as they might arrive higher than rpm?

 

[old 040]

How is it possible that when the points float the rpm increases and the spark continues? Some expert can explain it to me thanks

How did you conclude that the points are "floating" in the first place?

 

[heimannm]

"Point float" was a problem on V8 engines with points ignition systems since they had to open and close 4 times per revolution to fire all of the cylinders in sequence. With that many bumps they would eventually start to bounce when the closed and not complete the circuit long enough to saturate the coil and the spark would become weak and inconsistent.

As I understand the story, some McCulloch karters discovered by accident that if the spring on the points broke and the points were allowed to just bounce around they could get even higher RPM from the engines.

Heavy - I recommend you do a bit of internet searching and try to find some of the background yourself. I doubt you will find many guys on this site or other chainsaw sites that know much about it.

Mark

 

[Al Smith]

Do a "google" on Duffy Livingston .

 

[Redfin]

Im needing a dog for a Pm 850 if any of you have one to spare.

 

[Heavy]

eg served his time as a Fitter and Turner at BHP in Newcastle, completed Tool

Making at Technical Collage and later worked as a Leading Hand at Stewart and

Lloyds. His knowledge as a machinist and engineering allowed him not only to design

and manufacture karts from the ground up, but able to work with the very fine

tolerances required in modifying small motors to gain maximum performance.

Reg Massie, along with the support of his wife Fay designed and manufactured Karts

during the early to late 1960’s from his showroom and workshop at 114 Maitland Road

Islington.

The earliest design was the Massie Dirt Kart, which he designed and manufactured

with his brother Royd Massie. As the dirt tracks were replaced by hot mix and tyres

changed from grooved to slick, a new model Massie 85 Kart was designed weighing

87lb and powered by a part reed valve and piston induction Mac10 engine.

To improve performance, the Massie 85 was completely redesigned and rebuilt by Reg

Massie and brother in law Max Gleeson to produce the Massie Escort. The Escort had

new bucket seats, improved lighter frame and steering. All components of the Massie

Karts were manufactured and machined in Reg’s workshop or locally. To reduce

weight, the disc brakes, wheels and many other parts were cast from aluminium at a

local foundry in Wickham.

Following the introduction of the American McCulloch Kart engine, Reg soon

discovered they offered a wider scope for increasing performance as they had accessible

transfer ports that allowed for easy modification by enlarging and reshaping using

fiberglass resin. The McCulloch had six transfer ports, Reg added another three

opposite the exhaust to significantly increased performance. Enlarging the ports would

deliver three times the air fuel mix. Another simple modification was free-porting the

exhaust.

The McCulloch engines were fitted with reed valve inlets and diaphragm carburettors

with high and low speed mixture screws allowing fine-tuning during the race. Reg also

fitted the engines with triple carburettors. At the time he used 100% alcohol fuel.

Another way Reg increased performance was to advance the timing and bypass the

ignition points with a switch giving 27 degrees advance, once the motor reached certain

rpm, known as Maverick spark.

Reg and Max improved on this by fitting a second set of ignition points, when switched

over giving 48 degrees advance peaking at 23,000 rpm. The downside was that due to

the engine firing halfway up the stroke, if the driver didn’t switch back before the revs

dropped, the con-rod would disintegrate. This was in the days prior to electronic

ignition. Hi to smith, the only thing I found on the internet about maverick spark

 

[PogoInTheWoods]

There ya go!

 

[Al Smith]

Without going into 200 pages of explanation Duffy Livingston found by accident about a broken points spring .They surmised at what ever RPM's it was that the coil fired by itself without the points .
With a magneto the faster it goes the more lines of magnetic flux it cuts with a certain time period .Thus faster means a hotter spark up to the point the coil is saturated or in other words not be able to produce a higher voltage at increased RPMs .
I'm not aware if the practice of eliminating to points was ever used or not .Never the less no matter 40 plus degrees of advance or not a Mac 10 engine if it could hold up at 23 thousand RPMs ,.It might do it for a very short period of time .Keep in mind because I was there during the two cycle kart era ,a highly modified Mac engine was good for about 1 hour of racing before a rebuild if it lasted that long .They only ran at about half that speed which must have been fast enough because they dominated the kart circuit .

 

[Heavy]

Al smith write me the link Duffy Livingston found by accident about a broken points spring tell me where can I find it.

 

[Bigmac]

Maverick spark is what your looking for, do more research, the dual points is cool but not what your looking for, and you I don’t think want 48 degrees of advance either, Maverick spark is the only real way to advance the timing besides the limited amount possible by setting the points gap open to the max, with stock components. Maverick spark is what the factory was doing with the 5 degree flywheel, it doesn’t advance the timing at low rpms, only once it goes Mavericks, you can advance the flywheel, but at low rpms the points still control timing.

 

[heimannm]

See "Maverick Spark" on page 2...

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

Mark