pp cranks?

[david a luciani]

Hi guys,

i am all about curiosity sometimes.
few days ago i was looking at the pp cranks on the vintage site.
to be honest they looked like crap all brown with what looked like rust.
got in touch with Robin made an offer bought them.

i knew i was risking buying trash but p.p. cranks are rare and i wanted to see if they were salvagable.
well today was a generally crappy day for everything.
finally dragged home and the box from the kart shop was in my garage.opened up and the cranks loked pretty bad.
but it turned out to be minor surface crap and old dried up grease.
also got a mc5 crank though it was call a mc6 crank.


washed them good gave them a quick vibe and i guess i'm pleased.
they look really good.the mc5 crank came out pretty mint too.
ONE problem.
I AM CLUELESS AS TO WHAT THEY ARE!!!!

three were polished at some point one of those has extra wt. welded onto it.
two were shortened on the pto side looks like with a hacksaw.
#1#3 have a wider point cam than #2 #4
two pto keyways are 180 degrees different from the other two pto keyways.
so two of the cranks have the keyway on the "top" of the pto two have the keyway on the "bottom" .
one looks kinda untouched might even be nos.
below are pix of them.
i've numbered them so let me kinow what i have if you can.
the one that's seperate is just a close up for general condition.

[Terry Bentley]

What you need to check if those cranks are 5.8, 6.1 or 6.4 motors. One looks to be a 6.1 crank. Early model cranks for the 58's were bad out of balance. Grinding off material around the rod journal really helped to some extent in lessening the slight out of balance when getting above the 6000 rpm range they normally ran. Early 58 cranks are very thick and bulky around the rod journal. Later 58 and newer 61 cranks had less material. Obviously tapered down. Still plenty more to remove, but way better than early ones.

Not perfect but one way to determine what strokes these are is to measure from top of rod journal to top off crank itself. A 58 crank should measure around .170/.180" and 61 crank will be close to .130" The 64 crank is welded and usually easy to spot. I have a box full of them around somewhere. Can dig out if needed for more info.

One other thing the early 58 cranks have noticeably smaller journal where the points cam is. Appears at least one of your cranks fits that description. These were prone to just shear off and flywheel passing you up. So cutting the fins down on flywheel and crank support is a blessing for these.