Had a dead stick in the Super Cub on last week while visiting a local club field that I do not belong to. Was flying up wind when the engine quit just about right in front of me, decided to turn and land down wind. The forecast was light and variable winds however only the variable part was true. The plane nosed over after touch down and broke the carbon fiber spinner. The engine seemed a little tighter so I didn't fly again.
Removed and disassembled the engine. While apart a few modifications were made as well. The crankcase looks to be an investment casting, the outside is not finished. I hope to include a starter in the future so the crankcase was setup on centers on the front and rear bearings and the nose was machined concentric with the bearings. This will make it easier to fit the Ephil 76 starter that I plan to use.
The crankshaft is a three piece design and looks to be robust. The crank pins are machined on the center throw and pressed into the front and rear pieces of the crankshaft. The crank is supported with 6002 bearings on each end and a 6003 in the center just ahead of the front journal. There is also a lip seal just behind the front 6002 bearing. The cam throws are wide to allow the tappets to ride.
The wrist pin bearings are individual needle bearings rather than a caged type, the journal end appear to the caged type. Should be fun getting the pistons back on.
There are two magnets on the cam to trigger the ignition. The hall sensor is mounted on the back case however there no penetration into the crankcase, I was expecting a hole there. There are very clear marks for putting the cam in time. The ignition failed on my first Roto and I sent it to CH Ignitions for conversion to RcExl, Adrian cut the stock pickup off and mounted the pickup on the front, just wondering why?
Both front bearing are double sealed along the the included lip seal. The bearings and the seal are shown below. They really didn't want the front bearing to leak! Should any oil get past the center bearing, a leakage port back the crank area is provided. There are five seals between the crank area and outside the front bearing. I do plan to eliminate the inner most seal on the 6003. A new SKF 6003 bearing and a 6002 Timken bearings are expected today.
While apart both exhaust valves were cleaned. I'm using Red Line Racing oil at 40 to 1. The carbon deposits were on the soft side and cleaned pretty easy with an Exacto knife. The parts were soaked overnight and more carbon was removed. I don't remember how the valves were retained in the first Roto 85 purchased but I knew a tool was needed to get the retainers installed. On this engine the valves are retained with 1/8" E-clips. I know this because I dropped one while measuring to make the spring compressor. After a 30 minute search and rescue, I gave up and found a replacement. A clearance pocket was also machined for clearance of the plug temperature sensors. I had plug sensors installed but the fit was very tight. the pocket will make things easier for sure.
Really didn't find anything wrong but I'm replacing both front bearings. This engine had about 6 flights in 2024 and was my main plane in 2025 after the Champ crashed. I would image some like 75 - 8 minute flights in 2025 so there's 10 to 12 hours on the engine. All in all the construction is very nice.
