Rotex 25 hr. inspection issue

[redmark]

I did my 25 hr. Rotex inspection today and my forward cyls. 1 & 2 both had rich looking plugs but my number 3 & 4 plugs looked fine. Any ideas what the problem could be? Or is it a problem?

 

Thanks,

-Ron

[redmark]

I've also been told that this could be a sign of number 1 & 2 cyl. running cooler. It's been one of the 5 coldest December here and I've had a hard time keeping the oil temp up during the 25 hr. period.

 

Thanks for the help,

-Ron

[Jeremy MacGregor]

Make sure your prop isn't over loaded, should be able to turn at least 5300 in level flight, preferably more, @ WOT. Slightly darker color is nothing to worry about, sooty consistently at 25hrs and I would investigate further.

[Tom Baker]

Also if you are burning car gas some of the additives to boost the octane burn sooty, so the soot on the plugs does not always mean it is to rich. Tom

[Runtoeat]

Make sure your prop isn't over loaded, should be able to turn at least 5300 in level flight, preferably more, @ WOT. Slightly darker color is nothing to worry about, sooty consistently at 25hrs and I would investigate further.

 

Jeremy, you know a lot more about this than I do, and we've certainly talked a lot about this on this forum and the other, but don't we want to see rpm's more towards 5600 to 5700 rpm in WOT operation during level flight? I'm seeing 5200 @ zero flaps 65kt WOT climb leaving the runway and 5700 rpm WOT level flight. Wouldn't 5300 rpm WOT @ level still be on the low side for rpm and result in the engine being lugged down below 5000 during the climb outs?

[redmark]

Thanks for all the help... I feel better about the rich plugs now... the 25 hr. inspection required an oil change and I idled the engine that morning for at least 10 min. getting the oil temp up so that I could change it.

 

-Ron

[Runtoeat]

Hi Roger. It would be nice to be able to drop in and see the "prop doctor" and get my prop re-pitched but Tucson is a little too far from Michigan. My plane flies so well that I hate to mess with it but there are a couple of guys around here who know how to adjust the pitch on CT's. With the cold air temps, I do have tremendous climb capability and the pitch does work well for the short grass fiields I fly into. My plugs were a nice tan color at the last annual. Although I like the good climb performance, I'll consider your recommendation to go with a little more pitch.