Motoplat Flywheel Mystery

[Keith Meatyard]

This doesn't make sense based on what I've read and discussed with knowledgeable Pentoneers.  I have three 73 Jackpiners with Motoplats.  Two flywheels have 26mm, 1.5mm pitch threads.  I discovered that, when attempting to pull a third one with my puller, and the puller wouldn't quite fit, that it has 27mm, 1.25mm pitch threads.  The kicker is, they all have 9600162 number stamped on OD, and either the letters CL (on the 26mm) or HM (on the 27mm) also stamped on the OD.  No one has been able to explain this.  Could the factory have screwed up?  From another brand bike?  The motor with the 27mm ran fine by the way.

Keith Meatyard

[Mickey Sergeant]

Could there be a possibility that the threads were damaged at one time and someone  retapped the threads and used a different size nut?

[Keith Meatyard]

The 26 and 27mm threads are the internal threads for the puller, and I can't see any evidence of ever being re-tapped from 26 x 1.5 pitch to 27 x 1.25 pitch.  Even BJ at Penton Racing couldn't find any information that explained it.

Keith Meatyard

[SouthRider]

There were "fine thread" and "course thread" flywheels and pullers.

I used to know which flywheels came with which threads, but it has been a long long time, and the details are fuzzy, but it had to do with the size or weight of the flywheels.

There was also a "Femsa" puller for Husky's with Femsa point type ignitions. I don't remember if we used that on the Pentons with points or not, but it seems familiar. It was very large diameter with course threads.

Basically with those 3 pullers we could pull the flywheel from just about everything that came into the shop during that era.

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"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."

1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax

[Keith Meatyard]

OK, I received the puller from Dennis Kirk which is 27mm x 1.25mm pitch threads which fits the oddball flywheel like a glove.  Even though I have two identical flywheels from 175 motors, and they have the same number 9600162 stamped on each, they definitely have two different threads.



Keith Meatyard