All,

I have an OS 46 FXi mounted horizantal in a GP big stick with a pitts exhaust. This is the first season mounted on this aircraft with the pitts. The four seasons prior it was on my Nextstar. I have flown the stick about 10 times this season the past five it has become progressively harder to start. I have checked fuel and vent lines, checked Carb attach screws and o-ring, Diff glow drivers and replaced glow plug. If I can not get it started after two or three attemps I put it aside and fly another aircraft. If it does start I adjust the high speed let it warm up idles fine but when I take off it starts running rough upon rotation. It usaully will keep running. I level out it runs fine loops rolls touch and goes no problem. Today same thing (it was cold at the field 37F) only this time it ran rough and quit. Enough, I need help. There is compression when the prop is turned I have not checked it when the engine is hot. I run the same fuel in my other OS 46, 55 and 70 four stroke no problems.

Eddym

When you checked the fuel lines, did you look at the line inside the tank too? It doesn't take much, even a pin hole can cause issues. Also make sure that the cylinder head screws and back plate screws are tight?

You could also have something in the carb.

How did it run with the Pitts muffler at first? If it ran good, I doubt that could be a factor. Some people claim that they need to pinch off one muffler tube to build back pressure for good fuel flow. This has never been my experience though. then again, I've never tried a pitts on a .46-FXi.

plug one hole in the muffler temporarly for troubleshooting...if it runs beter than do it permanetly
Good flyin to ya

plug one hole in the muffler temporarly for troubleshooting...if it runs beter than do it permanetly
Good flyin to ya

You'll probably have to adjust the low end with the pitts muffler, then go back and redo the high end. Put a new glow plug in it, even if the old one still glows orange. Replace all fuel lines even if you can't see any problems with the old ones. Are you running after run oil? If not, the rear bearing may be producing rust flakes that are buggering up the piston and liner.

Thanks everyone for your input,

I have used after run oil in the engine since new. Thinking back to the first flights it has bee difficult to start. I have reinstalled the stock exhaust. If it works that could be telling me I have an engine that is worn to were it does not have enough compression to compensate for the pitts./? I have the big stick set up in the tail dragger config this elevates the carb a little. Should I have tried running it on half a tank? This would provide more fuel surface area for the pressure to act on. If this does not work I will reinstall the pitts and adjust the low end. If it does work I will charg on it is a fun airplane to fly. The hardest part now is the weather up here in Minnesota the flying season is over except for the die hard brain deads like me. My next test flight may be on skies.

Eddym

Hey,
I have a brand new OS 46FXi. It is hard to start? The needle on the back of the engine is higher than the center line of the carb and fuel tank? I have to choke it a lot get the initial fuel flow to the carb? I put this in a Avistar and replace a 46 SF. The SF is a great engine never had any problems of any kind. I don't know if the rear adj. needle being mounted higer than the center line of the tank is an issue in sucking the fuel in, but is a problem I would like to resolve? The is no way I can lower the engine or raise the tank. The tanik is center line on the Carb., but the needle valve is higher and the fuel inlet is on the top??

ANY ONE CAN HELP??????