andrewskj

Have new os55ax in a great planes cherokee having all kinds of problems keeping it running tried F plug no results os 8 plug still problem does this engine need to go into a non cowled plane to perform . It runs great for about 3to 4 min then it burbles and dies in air . Tried leaning low end still problems I hear how great this engine is but I AM having a rough time figuring this out would love to get this to work starts great and idles great and opening throttle great until I get it in the air and that is where the problems start. Please advise all you os users and thank you in advance . Ken

alan0899

G'day Ken,
This problem sounds a lot like the problems I had with my 75AX, I tried plugs, tuning, until a very wise gentleman suggested fuel may be my problem,
So I mixed fresh fuel & all my problems went away.
It turns out, my fuel had been in the flight box for nearly 12 months, & was very stale, & a dark green colour.
I have moved twice recently, & simply forgot how old that fuel was.
So try fresh fuel, even borrow a tank full from a friend, & see if that is your problem too.

Cheers

JohnBuckner

My Feedback: (1)

Ken no this engine certainly does not need to be uncowled and here are a couple of my 55's and I have some more in various airplanes. You of course must allow plenty of air in through the front of the cowl and as always a minimum of at least twice the outlet are in the rear lower cowl at the firewall. You did cut out the rear bottom of the cowl, right?

Did you ever get some experianced help I mean there is a ton of it avalible up there at Vegas and at least three flying sites? You need to go back to square one, first off go back to the #8. Next set the mid range back to the factory default and the book list it for every version not all AX are in the same position and I forgot for the 55 I think it is flush some are a half turn less than flush.

Now please forgive me but I have to ask this question you do know where the midrange is don,t you? It is on opposite side of the where conventional double needle mid ranges are in other engines. That is it is on the side where the fuel line goes and not on the throttle side.

Also I fully agree with alan the Ax's do not seem to like old fuel and I recently had a bout with some bad fuel in this time a 95AX which a fresh batch of fuel immediately cleared up.

John

jetmech05

If the engine dies with the same amount of fuel in your tank everytime you could have a hole in the line inside your tank....with a full tank the hole is submemerged in fuel but as you burn fuel the hole is uncovered sucks air, leans you out and you die

Jetdesign

My Feedback: (8)

My guess is the high speed mixture is out of whack, and you are chasing the problem by adjusting the low end. Return all needles/settings back to exactly what it says in the manual. Start there, don't touch the low end, don't lean the high end out more than 1/16 to 1/8 of a turn. It will run if it is rich. Let it break in or at least run a few flights there, then you can start making minor changes.

jetmech05

I totally missed the engine part. I agree with garc get the engine broke in before tuning for best performance.

rlipsett

I had two 55 ax give me problems in 1 day. the problem was a combination of old fuel and fuel tank problems. One tank had a slight split in the tank on the brass tube inside the tank. after the fuel was fixed this plane ran great for awhile until I the fuel ran down a little and then the clunck would shift position and open the slit up inside the tank causing it to lean and die but at other times it ran great when I would restart it when the clunk had moved back to the other side of the tank and it would run great for several minutes with reduced amount of fuel in plane. the other problem was the fuel bung was old and the brass tubing moved easily in it which reduced pressure in tank and engine ran poorly in the air

jester_s1

An engine that will run well for 4 minutes is an engine that doesn't have anything wrong with it 99% of the time. I'd suspect the tank or lines also. You can verify that by starting the engine again right after the deadstick. If you see bubbles in the line at any attitude then you know the issue is in your fuel supply.

Jetdesign

My Feedback: (8)

Problems in the air could be lean top end, possibly compensated for on ground by fiddling with low end.

daytonarc

My Feedback: (5)

+1 if it is a little lean on the high end it will cause it to heat up durring flight to the point that it gets too hot and looses compression and therefore dies. Try to richen up the top end a little.