McBob's new Mac big gun Twin 101B's

[mcbob]

Hey Bob, just wondering, what pitch chain do you use for a race saw? I'd imagine a 1/2" would be faster than a 3/8". Skip tooth, carbide, round tooth, weirdo chain?

This saw could open the door to me running 1/2" full compliment Super Chisel chain but at this stage in our Hard woods we'll proberly run 3/8".

Normally i have a couple of saw chains preped as the timber is not disclosed before the event so you have to have a few just in case the organisers have been known to used various hardwoods instead of poplar for the speed events and hardwood just tears the teeth of a softwood chain as a few have experianced in the past.

A fella must be a good boy scout and be prepared as this twin is a whole new ball game.

Mc Bob.

[Jerry VanDeusen Jr]

Very Cool
Hey Bob do you have any links to chainsaw website with more pics of crazy nuts chainsaw like yours?
Jerry

[mcbob]

Well you could try Racesaws.com

http://racesaws.com/index.php

McBob.

[Tom Luttenbacher]

McB back in the day when my home town hosted a Loggers Festival with saw/axe cutting contests the last year or so, maybe 80-81 there were a few open saws using 125 and 250 cc dirt bike engines complete with expansion chambers. They were some kinda handful but my o my did the saw dust fly! Tom

[mcbob]

McB back in the day when my home town hosted a Loggers Festival with saw/axe cutting contests the last year or so, maybe 80-81 there were a few open saws using 125 and 250 cc dirt bike engines complete with expansion chambers. They were some kinda handful but my o my did the saw dust fly! Tom

Well Tom

That was my era as well saws with balls we have done very well running our Mac SP125C knocking off the new saws ie Stihl 088's and Huskie 3120's in the visually standard class.
The Bender blew them out of the water in the open division but we didn't get to run against a twin Huskie 3120 soooo this is to match or better it.
Plus once we know how the saw performs we can then decide if there's a need for more mods to the engines and there's alky as this saw is starting on good old pump gas.

I have another advantage that the others don't i have the young fella who built the twin Huskie as my operator so he knows what makes that twin 3120 tick.

Mc Bob.

[Dan Flanders]

Hey Rockabilly Bob-
Can you elaborate on the Ryobi solid state ignition module... I know that there are a number of people that would like additional information especially now that the ATOM modules are no longer being made. It would be nice to find a replacement for points and condensers especially for the earlier motors.

Hands down the baddest saw was the Predator small block V-8 at the Placerville event a couple years back. It took four of us to lift it. The Harley V-Twin was pretty impressive too for a 4 stroke motor.

[mcbob]

Well Flandoman,

Gee it's been a while since i seen your happy smiling face ..............

The Ryobi whipper snippers i get from a scrap yard a couple of k from my place
there's two types that i know of with the second unit being the better as it has no cutout
and these will press onto the centre leg of the McCulloch laminations snuggly ( 9mm sq )
you have to cut the earth tang of the ryobi lamination to frree the unit.
I tried bonding the unit onto the Mac Lamination but it didn't last so now all i do is spread the two outer segments of the laminations to lock it in place.

http://macbobaust.com/phelon.html

Mc Bob.

[John Miller]

Hey Rockabilly Bob-
Can you elaborate on the Ryobi solid state ignition module... I know that there are a number of people that would like additional information especially now that the ATOM modules are no longer being made. It would be nice to find a replacement for points and condensers especially for the earlier motors...

X2 Please.

I am very interested in learning what parts are/will become scarce and what type of parts and/or modifications will be needed to continue.

I'd also like to learn about any web-sites where like minded individuals are able to freely discuss performance modifications to McCullogh & other 2-stroke engines.

[mcbob]

Rertead the last two posts ....................

McBob.

[Dan Flanders]

Bob, you are THE Mac man!!! Thanks for all of your hard work compiling your Mac site, I know there are a lot of folks who utilize it on a regular basis and it is a wonderful resource.

A couple more questions regarding the Ryobi ignition (what is the part #?) ... I am still a neophyte at building motors so hopefully someone else will chime in where my understanding of the ignition system falls short. Just to be clear, you are using the Ryobi coil as a direct replacement for the Mc coil. Are you still using the factory points and condenser? I think I misinterpreted that you had found a replacement for points and condensers

A while back there was a discussion on the ATOM modules and the use of the Yamaha module in lieu of points and condensers. I think Steve O made the point that it wouldn't work because the timing of the spark at higher RPM. There are a couple of replacements out there for the lower-revving motors, but nothing for the higher revving Macs. With the saw motors it seems like you are idling or a full throttle, what happens in the low-mid rpm ranges? What about changing the timing for alcohol? Would you use a stepped key in conjunction with a 5 deg flywheel or ????

Have a good fall season and happy cutting.

Dan