If you look at the flywheel side of a EZ-start nut you will see the threads don't
start for a ways up in the nut. I always belt sand them till I get to the first thread. Not only does this ensure you can get the nut extra tight without stripping out the soft aluminum but it ensures that the pull start itself does rub inside bottomed in the nut like they many times do and melt your new parts or worse yet remove the nut and destroy it all. I also use a steel nut to fully set the flywheel tight on the crank then remove it and install the real starter pawl nut. You can get it tighter with less chance of stripping things. That nut needs to be tight, tight.

Never ever hold the crank at either opposite end while working on a engine. If working on the flywheel end hold the flywheel, the collet end hold the collet.
Never use any force being transfered accross the crankshaft.

danielplace1962 wrote:
I agree with all that is said here....BUT, I must admit that I've never tightened the nut any more than I could with my homemade wrench (3/8" thick aluminum bar with a slot cut into it to grab both ears of the dog)...never felt the need to, and never had one come loose. I have been running Zenoahs since the old peanuts...not like I've only run 1 or 2... I don't feel it needs to be THAT tight, and certainly never needed Loctite. Just my observation and opinion...nothing more. I like your work practices though Daniel, you obviously work smart.

FTR Zenoah tightning torque specs for the rotor is 150 kgcm which is a little under 11 ftlb. That's not much. We hand tighten more than that easily.

The RCMK's do need to be tighter I believe because the flywheel taper isn't as closely matched to the crank as a Zenoah's is. Then there is the clearance issue that the RCMK's typically have with the starter clearance to flywheel nut. That issue lies in the pull start itself. If you measure the relaxed and extended distance the starter throws you will quickly see why they need a closer tolerance than a Zenoah. They don't relax as far back in the starter or extend as far. They are like .060 short in both directions. I have never had or heard of a issue with the Zenoahs flywheel coming loose but it is not uncommon to hear of a RCMK and I have had to repair the carnage on several. That is the reason a RCMK needs to be very tight and some locktite doesn't hurt at least if the flywheel seats itself on the crank farther then the nut will not fall off and allow the crank and flywheel to both be destroyed. Then hopefully you notice it contacting the source coil and retighten it with out further damage.
I own about 10 RCMK's and modded dozens more and work on them often and they are a different animal but once you learn there problem areas they are a awesome engine. Honestly in two years of running RCMK's almost exclusively I have never twisted or otherwise even had a RCMK upper or lower rod bearing or wrist pin need replacement and we are talking wide open stuffs on a few occasions without cowl. The lower half of upper rod journal will never get needle indentations from hydralic abuse. Never had to buy one single replacement crank. Just hasn't happened. They are truly amazing just how tough they are.

Daniel, thanks for the explanation on the RCMK. Obviously you have much more runtime on them than I do. I was not aware that they had issue with flywheels coming loose.

Daniel- how often does this happen to the RCMKs? I just bought two, want to keep them running well. I'm a sport boater, I dont have all of the tools others have... Which tools are the best to pick up, when I go to purchase some?

Just clearance the pullstart properly and tighten the flywheel nut real tight (with some locktite)and it is a non issue. From the factory if you use a thin front mount plate there is not enough clearance. It will start, idle and seem just fine till you throw it in the water and the prop thrust pushes the crank another .020 farther forward the the nut contacts the pullstart and baqd things happen. If using thin mounts you will need to gain some clearance. Usually .030-.040 by one of three ways

1) Remove the flywheel nut and take material of the back side and replace.

2) Add a washer or two to each of the three front mount spacers.

3) Add a washer or two on the bolts on each corner of the pullstart itself.

The small side of a Zenoah sparkplug wrench fits the center of the flywheel nut.
You can hold the flywheel if your careful with a long 6mm bolt screwed in the flywheel and rotating slowly till it hit a web of crankcase. That is not the preferred method which is a 2" X 8" flat aluminum or steel piece notched out
to clear the flywheel center and nut with two holes matching the two flywheel holes and screwing in two 6mm screws.

I use the long 6mm screw against case webbing technique to lock in the flywheel, but as Daniel pointed out, there are tools specific to the application. Here is a fine kit from CC Racing Engines. At $35 it's a good tool kit to have if you're going to be working on engines a lot and can't make your own.

www.cc-racingengines.com/index...emart&Itemid=53

Thanks guys. I could certainly use 6mm screw, but I think having the right tools would go along way! CC will be getting an order from me shortly!

From what I can see the CC tool will not secure the flywheel with the EZ starter dog/pawl in place. I hope I'm wrong, I'll get their tool too if it works, anybody?

The 6mm bolt in the flywheel won't work with the EZ starter dog/pawl either as it is larger than the stock one and covers up the 6mm flywheel bolt holes (this is what happened when I tried it). The 6mm bolt in the flywheel works fine for removing the stock starter dog/pawl though.

Thank you.