rotax 447 engine failure

by tim HEYLBUT in 2 Stroke Technical Questions 12 years ago

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Re: rotax 447 engine failure

by tim HEYLBUT » 12 years ago

tim HEYLBUT

4 27 0

Damn 6800rpm if I adjust the ptch to rev to 6800rpm I cant get out of ground effect? it was origanally pulling 5800rpm on the ground so we adjusted prop to get 6000 rpm and flew but nearlly doubled my take off and climbed out not that good? tried the 50"/32pitch 3 balde prop reved to 7000rpm but could not climb out and mechanic had to level off at 100 ft turn and land.,so went back to origanal 3 blade power fin 56"ground adjustable pitch...

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Re: rotax 447 engine failure

by tim HEYLBUT » 12 years ago

tim HEYLBUT

4 27 0

Hi bill its a single carbie,but checked and compared carb slides in all 4 carbies and checed the speed to make sure there not sticking or such,but thay all worked the same all specs set to factory,factory recomended jetting etc...??

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Re: rotax 447 engine failure

by bill martin » 12 years ago

bill martin

10 757 0

Tim,

You might try moving the needle clip up one notch to lower the needle. This would lean the midrange and increase the midrange EGTs. Doing this would have very little effect on the WOT temps and should help the bogging.

Bill.

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Re: rotax 447 engine failure

by tim HEYLBUT » 12 years ago

tim HEYLBUT

4 27 0

yep tried that also,have both 3 slot and 4 slot 15k2 needles and have tried all slots up and down,no change at all? so have reset to 2nd slot from the top,with rubber o'ring on top(slot 1 from the top) . also barely changed heat range?

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Re: rotax 447 engine failure

by Dennis Richardson » 12 years ago

Dennis Richardson

1 153 169

Sorry for your frustrating time. I have followed your thread and probaly understand what you are going through more than most, 2-cycle engines have been part of my professional and recreational life for 50 years or so. Point ignitions are a simple mechanical device, however they are subject to wear and require regular maintenance. Enough said on that but I think I see a communication misunderstanding on WOT setting.
WOT is determined in level flight. Setting the pitch to get as close to 6800 as you can without allowing it to exceed 6800 should give you a static rpm of about 6300 and a takeoff rpm of 6500-6600 rpm which is where a properly tuned 447 develops its maximum horsepower. Cruise rpm at 80% power will be about 5400 rpm. Operating at a higher rpm serves no purpose as the engine starts to overscavenge and you develope less thrust. Operating at a lower rpm does not utilize the full potential of the engine.
The jetting charts are set up for an engine running at this pre-determined rpm. If you pitch the prop for a lower operating rpm you will find that it is operating rich under load. If you correct the jetting for this low rpm condition you will find that on a partial throttle descent your egt's will rise and you run the risk of a lean burn failure. Engines continually operated with a course pitched prop usually exhibit excessive carbon build-up.
It is critical that your tach be accurate for these adjustments, consider verfiying its reading with a diagnostic device.
Dennis

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