A well tuned Moki needs nothing more than some 0 to 5% fuel and an OS F plug. (I use 5%) at 400 ft elevation Sideways, inverted or up right these motors are hands down the best on the market. I would suggest pulling the carb off the motor and give it a good cleaning. Remove the low speed disk and use a soft brissel tooth brush and some after run oil and give it a good once over. Check the O-Ring for seal when you put it back in. If it is lose then order a new one from http://www.hobbypeople.net/guru/HPS_317551801.asp
**************** part # 214539 - 10.180/21 - Mark Engines O-Ring - Mark 180/210/360 Carburetor $3.00 ***************
Also pull apart the needle and give it a good once over as well. Squirt fuel thorough all areas with some force.
Set the low end disk at the center mark
Set the needle at 1 3/4 turns out - adjust once you get her running
Use a 20x8 prop
Make sure your tank is using **large diameter fuel lines**.. This includes the clunk and brass tubes
Center the tank stopper/ line out let with the carb as close to the fire wall as you can.
Prime the motor ( get it really wet.. when you think there is enough give it a little more)
Hook up the glow driver and bump the prop backwards.. Watch your hand because she will get ya...
Low to high transition should be smooth the 5% fuel will help in this area. Make sure the low speed disk is seated all the way in the carb body. The O-Ring is all that holds the older ones in. If you are getting air sucked in it will mess with the low to high mixture. For the transition you should be using the disk for finite adjustments after you have properly set the high speed side. Very small adjustments should not make it harder to start...