by Jeffrey Fritts » 5 years ago
Thank you, thank you to one and all.
Problem solved and the 914 now produces full power and runs as smooth as melted butter. I was beginning to wonder if the engine had a mind of its own and was being defiant because it did not want to fly again. The accident that started all of this when the Kitfox took an excursion off the side of a remote bush airstrip during a takeoff ended with the poor plane on its back. We all know that the shinney side is supposed to be keep right side up and not on its back playing dead bug.
Anyway, your hints and tips were very useful in troubleshooting the problem. And the winner is...Todd Ison with his float bowl gasket thickness and the corresponding float bowl bolt being too long. Another source that confirmed what all of you were saying about warped, overtightened float bowls was Brett Lawton of Leading Edge Air Foils (LEAF). I had mentioned that a 5-year rubber replacement had been done and of course the carbs were rebuilt. The new style black neoprene float bowl gasket is indeed thinner than the old green paper gasket. When proper torque is applied to the float bowl bolt the bolt bottoms out and in this case did not compress the new gasket enough to complete the seal and was leaking air pressure at higher RPM. We shaved off 5 thousandths from each bolt and low and behold everything was fine again. Brett also mentioned a nonfactory approved tip that some 914 operators had done to improve the float bowl seal and they added a bail from a 912 carb to better secure the float bowl. Rotax #963 180 In looking at the Rotax IPC some of the carb overhaul/gasket sets may still come with the thicker paper gasket, so check that out when doing carb work. The devil is in the details or those pesky footnotes at the bottom of the page.
It is hard to believe that a few PSI of manifold pressure and a few thousandths of an inch could make such a difference.
Thank you again.
Jeffrey Fritts, USAF (ret.)
www.flywwlsa.com
"In aircraft maintenance, good enough is not good enough."
by john gunn » 5 years ago
... a classy response there, mr. jeffery,
Nice follow thru w/ credits & shows the power of this forum via its people.
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