Good old number 29

This is on the Facebook Yamaha Aircraft Conversions page. I wish I could buy this one, myself. 

Put your prop info and jetting here. There is a lot of mixed info on props and static rpm. Please put down the raw data, then expand on it if you care to. 
Rotax 503 DCSI
Powerfin “B” blade 
68” three blade
Set .025” from finest pitch
STATIC RPM and TEMPS
6,500 rpm max, down to 6,300 
EGT 1,025
CHT 425
Ambient temp 30° f
Main jets 158
Idler jets 45
Needle jets 2.74
Needle 8L2 in position 1 (top notch)
Air screw out 2 turns
I haven’t yet put a protractor on the prop to measure the pitch. Powerfin set it up to be adjustable using feeler gauges to measure the pitch, and that is how I set it up. This is the initial setup on my plane, which I intended to be more toward climb performance than cruise. The plane had 145 main jets installed when I bought it. I honestly didn’t see much difference in EGT with 150, 155, or 158 main jets. It never exceeded 1,100°. CHT was pushing 450° with prolonged pulls on the 150 jets, so I worked back up to the factory recommended 158s, and saw a minor decrease in CHT. Keep in mind that this is all static pulls, so it should drop with increased airflow when it’s actually moving. Plugs look nice and tan. I got the lowest CHT, about 400°, at 6,100 rpms and .040” on the prop pitch. I’ve seen a mix of opinions on redline, varying from 6,200 to 6,800. CPS quoted 6,800 max rpm for up to 5 minutes. Being that they’re a licensed retailer, I believe that’s accurate. Other information suggests 6,500 rpm as the continuous redline. I have no intention of running it continuously at 6,500. I do want to be able to reach 6,800. Snowmachines with the 503 revved to 8,000. With the plane locked down and the engine warm, at this prop setting, the rpms jumped as high as 6,500, then quickly settled at 6,300, fairly steady. I did notice that the engine would do that at full throttle, regardless of pitch or jetting. I’d see an initial high rpm, then a drop of about 200 rpm over the course of a minute, in correlation with the rise in CHT. EGT remained the same. All the carb setting are factory recommendations, except the air idle screw. I got the highest idle at 2.5 turns out, and turned it back in 1/2 a turn. 

I just diagnosed this most irritating problem and hoped that this solution might benefit some others. 
The 503 in my Kitfox is fresh. It’s jetted right. It has new spark plugs. It has new points. The point gap and timing is good. It has good spark. It has good compression. It has good fuel.
I trailered it to the airpark for some taxi time, but when I got it off the trailer, the number two cylinder (the rear cylinder) was not firing right. I messed with it for a couple hours, but the same thing kept happening. The rear cylinder would miss, then eventually go completely dead. The evidence of this was plain, with low egt and cht on the number two cylinder. The number two spark plug was wet with fuel, while the other was dry. I didn’t have spare plugs with me, but it had a great spark at both plugs. I took both plugs out and spun it over to blow the fuel out. I switched the plugs. I eventually pushed it back to the trailer because it kept doing the same thing. I could clear the cylinder, dry the plug, fire it up, but it would immediately start missing on number two, and eventually that cylinder would stop firing completely. 
I replaced the new NGK B8ES spark plugs with brand new NGK BR8EIX iridium plugs. I checked the carbs and floats. The float needles were properly in place and the floats were floating in the fuel in the bowl, when removed. I pulled out the slides and checked the needles. I lifted up the tail, to level the plane, and fuel came out of the air filter. The fuel valve was off. I double checked the jets, floats, and needles. All good. I started to remove the engine to see if the points were arcing, but the spark looked good, so I put it back together. The points are brand new, with only one hour on the points. The manual recommends readjusting them after ten hours, because they will wear where the cam lifts the breaker to open it. Knowing the gap would be lessening as it wore in, I made the initial adjustment toward the upper end of the range, giving them a wide gap. Certain that the carbs were properly set up, I surmised that it may have flooded the engine while bouncing down the road on the trailer. Being tilted back, the fuel would flood the back cylinder. This was not the case. I put a torch to it and made sure there was no gas in the cylinders. I put it back together. Same thing. Fired up, starts missing, number two takes a number two. So, back to the points. I started taking the engine off again. As I worked, I noticed gas on the floor beneath me. The fuel valve was off. The fuel lines, I left connected, and removed the carbs from the engine. They weren’t leaking out of the vent tubes or overflow. I had taken the primer hoses off of the nipples on the intakes, and it was dripping. I had noticed before that the primer seems to push the fuel back and forth a bit, instead of a steady push in one direction, but the primer had been working, and the engine had been running fine, so I hadn’t thought much more about it. The fuel to the primer isn’t shut off with the fuel valve. There is a tee on the bottom of the panel tank. One side of the tee goes to the valve, the other side goes to the primer. I capped off the fittings and plugged the primer hose. I put everything back on the engine and put the cowl back on. The engine fired up and ran great. Thank God for little things. If this had happened in the air, it would have been a forced landing. Even if the fuel valve could have shut off the fuel to the primer, it wouldn’t have kept it from dripping while the fuel was on. It’s pretty hard to start cold, without the primer.  If I rebuild the primer, I’ll put a fuel valve inline, so I can shut off the fuel to just the primer, so it’s never a problem. Because the plane was tilted back, whether on the trailer or on the ground, the fuel was dripping into the back cylinder and flooding it out. Inflight, it could have drowned them both out. On one cylinder, I could keep it running, but it wasn’t pulling hard enough to move under its own power. Putting in a valve to shut off the primer while it’s running would be a good move, even if you’ve never had a problem. Mine was fine for over thirty years, until that one day it wasn’t. It would be the same with a dual ignition. It was great to hear how smoothly it ran, once I figured it out. Now I have another project to work on, but it’s huge load off my mind.