Author Topic: 101 mac offset flywheel keys  (Read 337 times)

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Offline Snoopy

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101 mac offset flywheel keys
« on: December 30, 2015, 09:04:58 pm »
I have been told you could get off set flywheel keys for 101 macs. If so where could I get them? Thanks!!!! ;D

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Offline awol

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Re: 101 mac offset flywheel keys
« Reply #1 on: December 31, 2015, 01:58:14 pm »
   I have a couple of the 5 flywheels, but they both have broken fins and starter pawl issues. I have been running a couple of the std flywheels keyless, and just advance them a few degrees. The MC40 that I ran in West Plains was done this way. I set the advance using a degree wheel, I think it would equal a little less than a third of a key width for 5 advance.
    I have never heard of offset keys for these engines.
New ported Husqvarna and Jonsered saws. Woods porting of saws by appointment.

doittheoldway@gmail.com  417-259-0248

Offline Snoopy

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Re: 101 mac offset flywheel keys
« Reply #2 on: December 31, 2015, 03:04:10 pm »
Ok thanks for the info :)

Offline Al Smith

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Re: 101 mac offset flywheel keys
« Reply #3 on: January 01, 2016, 07:51:50 am »
One of my 125's that came from California has an off set key .

Keep in mind though unless you are running an "atom Arc"( solid state ) type trigger all you are doing is shifting the flywheel ahead .This is to keep the fire point in the max lines of magnetic flux for the hottest spark . With points they still need to be "mavericked" .In other words reset from 18 thou opened to maybe 22 or so .You'll  have to play with it because quite frankly I forgot exactly how much it is .

The solid state triggers switch at the max voltage generated from the coil .When the sine wave shifts negative ,they fire .

Offline Al Smith

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Re: 101 mac offset flywheel keys
« Reply #4 on: January 01, 2016, 08:00:33 am »
Rambling on .Most Macs are set at 26 degree advance .With points and no off set you can get a few degrees more ,maybe 29- 30 .Keep in mind with a 101 if it comes back on you from a pre fire that thing has enough grunt to try and pull your arm out of the socket .I had an 084 Stihl  prefire and break a bone in my hand .So it's a fine line between being able to start it and having it turn into an arm breaker .

FWIW I have a Mac 610 the 70 cc model with advanced timing that can crank on at over 15,000 RPM ,still four stroking .

Offline awol

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Re: 101 mac offset flywheel keys
« Reply #5 on: January 02, 2016, 10:06:24 am »
    All the points are there for, is getting the engine started, and up to speed. While running at speed they never completely close, and the firing point is adjusted by flywheel position. I have proven this by installing a toggle switch between the points and coil, and mounting it on the saw handle. The point at which the spark begins to maverick without the switch however, is adjusted by breaker point return spring pressure. I have seen some special points, made some aftermarket kart mfg. that had a Z spring, making it much easier to bend and adjust the pressure.
   The good part about running an engine with maverick spark, is that the points can be set conservatively, and yet still get maximum advance at full power. Saves them starters!
New ported Husqvarna and Jonsered saws. Woods porting of saws by appointment.

doittheoldway@gmail.com  417-259-0248

Offline Al Smith

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Re: 101 mac offset flywheel keys
« Reply #6 on: January 02, 2016, 11:17:33 am »
It seems to me one of those old Kart racers said exactly the very same thing .Duffy Livingston perhaps .

This I do know if you set the points too far apart they won't fire because they never close at cranking speeds .Then again at cranking speeds the coil is not at max voltage output .

I like points  to solid state but many do not .

With the exception of the one model 125 and the 610 I've never done any retuning of a Mac ignition system .The 125 might be a few degrees advanced and the 610 just proving I could make a mid sized antique run about as well a modern saw .Never out ran one but hung pretty darned close .

 

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