RE: Moki Engines Thread
Nice to see a thread on my favorite engines. I've been running Mokis for several years now (a couple of 2.10s a 1.80 and a 1.35). They are great engines and I love them. The 2.10 makes about as much power as a good 45cc gasser, so I use them to power all manner of large aerobatic aircraft. I currently have a 2.10 in a Great Planes Ultimate.
Once set up properly, a Moki will literally run for years without needing adjustment, but they do have a couple of quirks it's good to be aware of.
The 2 o-rings that seal the low-speed disk and keep it from rotating can shrink and harden with time. This can be hard to diagnose because it can't be "seen" when you tear down the carb. What happens as the o-rings loosen is that the low-speed disk then rotates due to engine vibration. On one of my engines, it rotated enough to completely block-off the fuel supply causing a deadstick situation.
The solution is to place a small dollop of silicon glue (I use the GOOP brand) where the low-speed disk meets the carb near the main needle valve flange. This solves the problem and keeps the disk from rotating. The silicon glue can easily be pried away for maintenance, tear down, etc. I only do this after break-in and once the low speed setting has been fine tuned. Obviously, the area where the silicon glue is to be applied has to be scrupulously cleaned and degreased prior to application.
By the way, I don't think I have ever had to adjust the low speed mixture once it had been set.
Another "quirk" is what I call the Large Fuel Tubbing Myth. Many users think these engines require all manner of special plumbing to ensure adequate fuel supply. I believe the originator of this thread mentioned something... Anyway, I don't mean to start a war, but this is false, what the engine requires is ADEQUATE FUEL PRESSURE. This must be supplied either by a pump or by a properly set up muffler. The commonly used BCM muffler (an otherwise fine product), sadly does not provide enough pressure to the tank, and thus the engine runs lean, overheats and quits.
Folks then start doing all sorts of silly things like using extra large tubing, drilling out their clunks (really) and so on. All you have to do is block-off one of the exit pipes on the BCM muffler and voila, great tank pressurization and fuel supply. BTW all my Mokis run on standard medium 3/32 fuel tubing. Though I haven't used them myself, Cline regulators are reputed to work well, if you want to place the tank in the middle of the aircraft.
I've had great luck with the OS "F" plug on all my Mokis and the following props for general sport flying:
1.35 APC 18X8
1.80 APC 18X10
2.10 APC 20X8