N 39991 Almost Ready to fly again

[Ragwing nut]

Re: N 39991 Almost Ready to fly again

clamp a board across the bottom of the control wheels to hold them firm and straight while riggin ailerons. make sure the turnbuckle on the column is adjusted correctly unless it is a prewar and does not have one. then adjust each wing to have roughly 1/4 droop, then tighten balance cable to roughly 1/8" droop. Make sure you have some tension on the balance cable, should be a little stiff until cables stretch some after a few flights, if not it will allow ailerons to float in flight some causing rigging issues.

as far as the engine knock, do a compression check for stuck valve. stuck valve does not usually sound like a knock, usually more of a metallic sound. You will also not get a full run up with a stuck valve either. Are you sure you are not hearing the impulse coupling clack?

[KewFlyer]

Re: N 39991 Almost Ready to fly again

Thanks Ragwing nut. Will pass it on and use next week end. Session number 2 of the rigging.

As far as the "knock", is like a hammer metal noise. It has two Case mags, by the way.

Thanks for the chime in.

I can use all the help I can get in getting the plane rigged correctly and the engine running smooth. We are almost there...I think.

Ralph

[crispy critter]

Re: N 39991 Almost Ready to fly again

A sticking valve in my experience will sound more like click or tick then a clang or knock....or sometimes will have a little pop thru the exhaust when idling. Also,they are correct on the ailerons,need to have at 1/4" to 1/8" inch droop on each side to get them streamlined in flight.

[KewFlyer]

Re: N 39991 Almost Ready to fly again

Kevin:

The sound is more like a knock rather thank a clang....if you can tell the difference between knock and clang .
On iddle, you will hear this metal sound on "low note" rather than on a high metal note...clong clong clong rather than cling cling cling. We'll keep at it on cylinder at the time.
Thanks
Ralph

[magman]

Re: N 39991 Almost Ready to fly again

Leaking Exhaust Gaskets are often mistaken for rod knocks.

Press Test?

[crispy critter]

Re: N 39991 Almost Ready to fly again

Magman,
You are somewhat correct but an exhaust leak will sound more like a high or sharp pitch tick or click and not a low pitch clong or clunk sound like he described above......
Ralph,
Have you pulled the oil screen and took a look yet?

[KewFlyer]

Re: N 39991 Almost Ready to fly again

Kevin:
Did oil change last May 2011. Screen was clear and cleaned and the oil was still clear. The oil was run thru a white shop rag and after 2-3 weeks, there were no visual solids or metal shavings present on the rag. No outside oil testing was made.

We are puzzled with the noise and inclined to believe that it might be the old Case mag click/clong, like someone in this forum pointed out. All compression are in the high 70s. Plugs are new. The engine develops fine, full RPM, smooth running. The "clong" is more noticeable in idle...maybe due to the reduced engine noise.

Keep all posted. and thanks to all for the assistance
Ralph

[Hank Jarrett]

Re: N 39991 Almost Ready to fly again

Have you tried listening to the "sound" while wearing an ANR headset? I know on my engine the headset allowed me to eliminate all of the steady, repeated noises and hear the intermittent ones much better. It was how I finally isolated a tapping intermittent buzz to the edge of a piece of heat shroud. Liked to drive me crazy and was fixed with a little piece of safety wire. It sure didn't sound like heat shroud before the ANRs were used!
Hank

[Mark Julicher]

Re: N 39991 Almost Ready to fly again

A mechanic's stethoscope could help you also.

[KewFlyer]

Re: N 39991 Almost Ready to fly again

Thanks to all.... N39991 flies again !!!! smooth as silk with some right rudder pressure even at 1,800 and up.... a trim tab is in the works. We think we have worked out all the bugs so far.
Remaining is the starting when hot with Case mags: in cold start, gets going at the second pull with one primer shot and 5 back blades.... after running/after hot it takes about 20 pulls or more to get the engine going. We tried with one shot of prime and 5 back blades, no back blades, two shots of prime with seven back blades, no back blades and no matter which combination we use, still takes 20 or more pulls before it catches. I can hear the tribe from here mentioning to replace those old case mags and get new slick with shielded harness, but $$$ are not in the budget at this time. We opened the mags and tested them, check the few parts and the appear to be in working order. Any suggestions?.

Also, got some 100 LL drops and streaks on the top of the fuselage leaving a nice blue stains. How can I remove them?

Thanks to all. Pictures are next.

Ralph

[M Towsley]

Re: N 39991 Almost Ready to fly again

Ralph,

As you shut off the mags after running, push the throttle to full throttle until the prop stops. If you are shutting it down at idle the carb is pulling fuel into the engine and flooding it as the prop winds down. I learned this the hard way years ago with my first T-Craft. If I remember correctly, this is the shutdown procedure in the manual for the small Continentals. Don't forget to pull the throttle back to idle after you do this so you don't start it at full throttle the next time around.

[Pearson]

Re: N 39991 Almost Ready to fly again

Remaining is the starting when hot....We tried with one shot of prime and 5 back blades, no back blades, two shots of prime with seven back blades,.... Any suggestions?.

Also, got some 100 LL drops and streaks on the top of the fuselage leaving a nice blue stains. How can I remove them?

Congratulations on getting it back in the air!!! All these little Continentals have their own way when it comes to starting. When mine has been flown within an couple of hours, I don't use ANY prime. Mine starts when cold with the throttle fully CLOSED. After I have flown enough to fully warm the engine, it will start with absolutely NO PRIME and the throttle open about 1/8". Maybe it will work with your engine.

If the gas streaks are allowed to dry it is a lot harder to get them off. The easiest thing I have found to remove them is more gas. I wet a rag with gas at one of the drains and wipe the stain off.

Waiting for the pictures!