need a Mc 6 flywheel

[steveohara]

Anyone have a Mc 6 flywheel they want to sell or trade???
Part # is 48785.... looks like a Mc7,8,20,30 on the front, machined off smooth on the back.
Will purchase or swap parts.
Thanks,
Steve O'Hara

[steve miller]

steve , i think i just put one on a 49 yesterday .. i thought it was somethin somebody customized try makin lighter .ill pop it off and take picture ..just curious but why did they do that.. i have a couple mc6s that came on a kart they both got 5 degree flywheels ..?

[Bob Towarnicki]

Steve,
Is this what you need? I always assumed it was a regular flywheel cut down to lighten it. If it is an original and you can use it send me a PM with your address and I will send it out.
Bob

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[steveohara]

Bob,

Thanks for the offer to help but you are right about the flywheel in the photos, it is a modern version that has been machined. I'm trying to make the motor with all the correct parts so I will keep looking.

Steve.... and any others playing with the Mc 6 engines... FYI the key position in the crank on the 6 is more advanced than the engines that came with the 5 degree flywheels so if you update the flywheel on a Mc 6 with 5 degree version from say a Mc 91 engine things will get every interesting when the points float and the timing is determined by the coil post/flywheel magnet relationship.
I didn't do a real careful measurement but I would guess the key position is somewhere around 8 degrees more advanced than a 91 crank so the spark timing could end up close to 40 degrees BTDC with the combination of the 6 crank and 5 degree flywheel.

Here is a general rule of thumb to help those who are interested.... testing shows that when the points float spark will occur when the leading edge of the trailing magnet in the flywheel is at the center of the middle coil post. With the correct flywheel for a Mc 6 on a Mc 6 crank and the points set to open at 25 DBTDC the leading edge of the trialing magnet will line up approximately on the left edge of the middle post of the coil which means it should act about the same as a 91 with a 5 degree flywheel. But, if you put the 5 degree flywheel on the Mc 6 that has the points set for 25 DBTDC you'll find that the leading edge of the trailing magnet is around a quarter inch to the left of the left edge of the middle post when the points open so the change in timing when the points float will be much greater.
Who knows.... it might like all that advance with the big thick head gasket that is used on the 6 but just be aware that you might be risking engine damage with that much advance when the points start jumping around.
Steve O'Hara

[Tom Smith]

Steve, Mc-6 flywheels look the same as the 1-71 saw flywheel to me. Also it looks to me like you could make one from an Mc-70 flywheel, pn 57946. You can have this 1-71 flywheel however it has a chunk busted out of one of the puller bosses. Normally I throw away flywheels that have any flaw but I know these particular flywheels are not real common. 1-71s have the same bore and stroke as the Mc-6 so the balance values should be the same. Maybe that's one of the reasons why Mc-70s shook themselves apart!
The Mc-6 and 1-71 flywheel backsides are as cast, they are not machined. Look closely and maybe you can see the remnants of the sprue just above where I wrote Mc-6 and the mold parting lines around the magnet boss in the photos. Machining an Mc-70 flywheel would work but it wouldn't be 100% correct.

[steveohara]

Tom,

As always, thanks for the excellent post and the offer to assist. I have two Mc 6s and I'm building the third one from parts gathered there and there so I consulted my two existing motors and found that one has the flat back flywheel and the other has the raised rings version. Being perplexed and thinking one of the existing motors must be wrong I contacted Lynn Haddock because I knew he had a NOS Mc 6 and asked him to check his to get the straight scoop on the correct flywheel.
You'll love this... Lynn and I each have a Mc 6 with the smooth flywheel and the Tilly carb and we each have a Mc 6 with the raised rings on the flywheel and the Mc flatback carb. I guess that means I need to decide which carb I'm going to use before I pick the flywheel
I have a friend coming over this weekend and we are going to use a fixture I made up to attempt a controlled straightening of the front axle on his Go Kart 800 chassis. I will take pictures as the process moves along so we can share the method with this site if it works. He saw my post and called today to say he thinks he has the flywheel I need so I will look at what he has and see if it will work. Otherwise i will take you up on your offer of the correct flywheel and see if I can fix it up to finish the motor.
Thanks!
Steve O'Hara

[steve miller]

Steve H. thanks for explaining the timming .im glad i never run them only on bench .i built em both outa parts ..im gonna look and see .. nice pictures tom now i have learnt somethin new today ..

[PAUL BENNETT]

Steve, Tom & Everyone who has contributed to this subject,

What an education! I never thought there were so many variations of the Mac flywheel until I got back into Karting Three years ago and started collecting parts. All of you have really helped refresh this old brain and helped make some sense of my pile of parts.

Steve, BTW the flywheel I have is probably a 1-71 ( cast back with rounded top on the keyway ) See you tomorrow. Paul

[Tom Smith]

Steve, I checked my other original Mc-6, it has a flat flywheel also so I guess now the score is Mc-6 flat flywheels are ahead 4 to 2, end of first inning. And then there are Mc-10 flywheels which are quite a bit different that all the other kart flywheels.

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[steveohara]

Tom,

Now I know why you sent me three or four Mc 10 flywheels... your file drawer was full!
Since the McCulloch parts diagram shows the Mc 6 with the smooth back flywheel and lists the flywheel as a different part number than the models that followed I like the smooth back version as THE Mc 6 flywheel so I will stick with that version if I get my hands on one.
Steve