About 6 or 7 years ago, when I first started machining, the Kerzel engine was the first hit and miss engine I ever built. After many trials and tribulations, I ended up with a successful runner. You can see the lengthy build thread here. http://www.homemodelenginemachinist.com/showthread.php?t=10091--Although this engine worked very well, and went into and out of hit and miss mode as I had hoped for, it never gave that distinctive "pop"---hiss-hiss-hiss "pop"---hiss-hiss-hiss sound that you associate with full size hit and miss engines, or even many of the model Farm-boy engines I have seen built. I decided that this was the result of my using a Viton elastomer ring on the piston instead of a cast iron ring. The Viton ring seals perfectly, but it creates more drag on the piston than a cast iron ring would. I have often wondered over the years, if an increase in flywheel diameter would have a positive effect on the way my engine ran. A recent post on HMEM by a gentleman named Jim, showed that he built a Kerzel a few years ago, and failed to get it running at all until he made a set of oversize flywheels for it. This got me thinking about my own Kerzel again, and prompted me to measure how much clearance I had between the existing 3 1/2" flywheels and the wooden base. I just have room to slide a 1/4" thick piece of cold rolled flatbar between the brass flywheel and the base. The gas tank can be slid over 1/4" more to the right to clear a larger flywheel.A phone call to my metal supplier determined that he has a piece of DOM tubing, 4" outside diameter and 3" inner diameter, and that he would saw off a couple of 7/8" thick "rings" for me for $5 each. Since I have exhausted my ideas of "nifty things to build" for the moment, I am going to see if increasing the diameter of the flywheels has any effect on how it runs. The picture here shows my kerzel, setting up on it's shelf, and you can see the 1/4" of clearance under the existing flywheel.
