vibrations

[CDE2FLY]

I'm running an IVO IFA medium on a 914 and last summer met with Dorsel to balanced the carbs using the Carb Mate which definitely smothed things out - especially at idle.

Later in the fall, Dorsel brought the Dynavibe to the North East Kitfox Fly-in and we balanced the prop. This resuted in a very noticable improvement across all RPM ranges. As soon as the engine fired, you could tell there was a substantial improvement. One of the advantages of the Dynavibe is that you balance the prop and the spinner at the same time - highly recommended!

[Monocock]

Cainbird

Don't forget to check the tracking too. I was amazed at how far out one of my tips was and that caused vibration in exactly the power setting range you have mentioned.

[egp8111]

it goes past red line at 5000rpm ! 4000 is about 80mph. I balanced the carbs at 2500 rpm but the were out of sync at the higher power settings. I'm using the dual cable throttle from McCarr. I dont see how to adjust the sperate cables.

[Peteohms]

it goes past red line at 5000rpm ! 4000 is about 80mph. I balanced the carbs at 2500 rpm but the were out of sync at the higher power settings. I'm using the dual cable throttle from McCarr. I dont see how to adjust the sperate cables.

EG,

Do you mean that your tach has a redline @ 5000 rpm? My understanding is that normal cruise is 5400-5500 rpm for The 912.

[egp8111]

sorry, not the engine redline, the airplane is pushing VNE(100mph) at 5000rpm. I've check the asi against the GPS and its pretty accurate. I'd be interested to know what others with a 912ul powered KFIII are using for cruise rpm.

[Monocock]

I'd be interested to know what others with a 912ul powered KFIII are using for cruise rpm.

Rotax clearly state that 5000 is where they are designed to be in the cruise and I know of some who cruise at 5400. I didn't like to say anything but 4000 won't be doing it much good, and the gearbox will be under more strain than it needs to be. There has been a lot of past discussion on various forums about this and people have provided some interesting stoies on the Rotax owner forum about the results of low revs in the cruise over a long period of time.

Out of interest, what's your static rpm on the ground? I'm guessing it's pretty low if you're reaching VNE at 5000 rpm. I might be wrong but it sounds like your prop might be set very coarse.

[cainbird]

Monocock,
Good point! I havent checked the tracking in a while. I will check it tomorrow.

Cain B