Since the "Cranshaft Shim" thread evolved into a CY cranks vs Zen cranks topic, maybe
a new thread is in order.

An interesting thread appeared on JRCBD titled "Zenoah 2mm cranks". Here is the text
from the first message (credit to Fielies) that got the attention of several. I'm not
posting this to say I think it's true. I am reposting it because a recent experience
with my own CY Stuffed/Stroker cranks was making me wonder if the CY crank pins are in
fact inserted extra tight. My new evidence was not as dramatic or clear cut as Fielies
so I decided to continue sitting on mine and present his findings here instead.

_______________________________

Fielies wrote:

>"Built a Zen 30,5 using the Zen 2mm stroker. After running the motor for some races,
>stripped the motor and found the crank slightly twisted. When i tried to staighten it,
>i found that it does not take much to move the webs. It is like the big end pin is a
>bit small and not as tight as the stock cranks. I fitted a new crank, and after a
>couple of races the same thing.

>I replaced the Zen cranks with CY Full circle 2mm strokers and no problem since.
>Has anyone had this problem? Are there pins available that might be a tighter fit, or
>do you have to get them custom made?."

________________________________

The only part of his post that I can answer with confidence is the "Are there pins
available". Yes, William T. Hutchinson, Co. can provide any high quality pins a boater
might need (thanks to JA for this tip):

www.wthutch.com/index.htm

Considering the CY Stuffed/Stroker was only designed to handle a 34mm piston at +2mm
stroke and Fielies is running a 36mm piston with no evidence of twisting has to say
something positive about the CY crank pins.

Beyond that, the jury is still out for me. In the mean time, I will continue using
CY Stuffed/Stroker cranks because in spite of the numerous ways I have abused them,
I've never managed to twist one yet - not that I can measure.

maybe they are not garbage with respect to the zenoahs after all? - Despite the mecca of speed findings

The CY +2mm crank has been slowly growing in popularity. Some want to work with the
+2mm stroke, others want to try the "stuffed" effect. Now, it looks like there is
evidence that CY is inserting a tight crank pin.

Rotors are no problem to install. Coat the conical fit with anti-seize. Torque it to
112 in. lbs. I'm done.

I seriously thought about trying RCMK's +1mm crank but if I have to beg the rotor to
stay on the shaft, that does not sound like fun to me. I sure am grateful to Dan for
letting us know there is an obvious machining error in those cranks. I'm confident
RCMK will fix it. They have had a lot of practice fixing all the other goofs they
keep selling to their customers. Does anybody know if they ever got around to improving
the crappy starters they sell with their motors. Hope so. As soon as I read those
RCMK rotors are fitting properly, I think I will have a go at one or two, but that
might be a while so I'll just run my CYs until then.
_______________________________________________________________
Edited 8-23-13

This is a thread on crankshaft pins. RCMK has a reputation for having a tight fitting
pin that is better than most - not that I have any direct experience that confirms it
for the reasons stated above. I will change the title of the thread and include RCMK
as they are one of the few companies making off the shelf cranks available for which
many boaters are grateful (me included). If anyone learns anything interesting about
how the different crank pins compare, hopefully they will post it here.

this is also for the same reason that i want to change to a c.y 2mm cranck. fielies and myself often speak to one another as we both race in south africa and like to share problems with our mods. i modded my first 30.5cc 2 moths back and since then lost 2 zen 2mm crancks! i like how my 30.5 run butt cannot replace the cranck after each gallon of feul, nor pay $150+ for a super cranck. i am prepared to give c.y a chance if I CAN GET 1!

The number of boaters joining the waiting list for CY cranks gets longer every day. Just
installed my only spare here so I'm on the waiting list too.

Those Zen cranks can give a lot more service with new pins installed. Easier said than
done though and I'm sure you already knew that. Didn't JA refer to someone in S. Africa
with the tools for installing pins so maybe he could steer both of you guys in that
direction???

I've been interested in the 30.5cc builds though I've never attempted one. When you
have time, please list/describe the parts you selected to make yours. I'm certain others
would be interested in a thread like that also.

The person who is E-mailing me is named Fielies.

Not sure there is really any machining error on the RCMK cranks. If you seat the flywheel properly they will never come off. I have heard of as many or more Zenoahs that have come off. It is all due to not seating the flywheel properly after reassembling the engine. Think it just takes a bit more force to seat a RCMK flywheel versus a Zenoah.
They know they aren't holding the flywheel properly and therefore because they are afraid of twisting the crank they don't tighten it on like they should. The flywheel needs to be held with the proper tool and the flywheel seated with a steel nut till you feel the flywheel fully seat and the crush stop. Then you remove it and replace it with the pawl nut.
I have about 20 + engines with RCMK cranks in them in RCMK's and Zenoah's with either flywheel on them and haven't had any come off but I hear or see them doing so quite often and it is even more prevalent since the advent of the EZ start because it blocks access to the holes in the flywheel we usually use to hold it with.
The RCMK cranks are much better cranks than Zenoahs and a CY I would not run if you gave them to me. Had build several engines with them and they will not work in the engines we run today. It just does not work. If they work for you that is wonderful not knocking what you have good luck with just stating my experiences with them.