hoppy

I've tuned an engine per break in instuctions and it has actually been in the air four times. But after a tree jumped out in front of my plane, (a trainer) it wants to quit when I lift the nose of the plane more than 45 degrees.

I don't see anything loose or bent etc. The hose in the fuel tank seems intack however I can't get to it.

The engine is a 0S LA 40. It really ran great before that damn tree. Does anyone have any ideas?

Oh yeah, there is also a vibration that wasn't there before the wreck.

javven

Balance your prop. Check your spinner (for the vibration). If in doubt replace both. What kind of prop was it? If it's a MA nylon prop it should still be ok.

Bad news is it could be a crank slightly bent (which just sucks).

Hope others can re: in on the engine-run problem.

spuck5644

You are too lean,,,meaning you engine needs to be richened up a bit. The vibe is probably from a prop or spinner that is now out of balance. Hope this helps,
Steve
Puckett Model Aviation

MHawker

My Feedback: (16)

I would start from the basic fuel line connections (as well as pressure line) and go to the mixture settings, etc. The vibration could be things like prop (don't know if you replaced it or if it broke), a crack in the nose somewhere or firewall, etc.

May be worthwhile to pull the engine and check the mount structure.

Good luck!

Mike

TRP

My Feedback: (1)

damn trees....

hoppy

Actually I didn't think a spinner would cause vibration. It probably is badly out of balance because my starter keeps spinning on it an creating deep grooves. The prop is balanced ok because I did that before I tried the engine again.

Thanks.

Flying Hog

Try This.
Take the plane with no fuel in it, Hold it strait up with both hands and shake it in a downward motion. The clunk in the tank probably went forward when you hit the tree.

Longaly

I was going to suggest checking the clunk as well.

MinnFlyer

My Feedback: (4)

I was going to say that too, but many times shaking it isn't enough. Pull out the tank and make SURE that the clunk has not been whipped to the front, and if it has, make sure you get it back where it belongs.

hoppy

What's the best way to get to a fuel tank when it's surrounded by a balsa? I can see it from the inside through the "brace with a hole" (terminology wrong sorry) but it's glued in and no way to get the tank out.

MinnFlyer

My Feedback: (4)

Ewww...

Ok, try this...

Empty the tank, and then hold the plane nose up without the wing (someplace where you have good light). Then gently wiggle the nose and see if you can either see or hear the clunk moving around.

If you can see or hear it, the problem is elsewhere. (although it could also be that the fuel line has become disconnected inside the tank which would require removing the tank anyway). If you cannot see or hear the clunk, try the shaking method, sometimes it works, but not often. What the plane needs is a good rearward shot (similar to the forward hit it took when it hit the tree). Keep trying till you can see or hear the clunk.

As far as removing the tank goes, it would help to know what what type of plane it is.

hoppy

MinnFlyer,

I can hear the clunk moving around. I've already tried what you suggested by looking for it but can't see it too clearly. I thought maybe the line inside the tank may have come off.

The plane is a Hobbico Superstar 40 trainer. It was prebuilt. Someone has already suggested that the engine is running to lean which could make it do that. Is that true?

Also, would a worn out spinner, (grooves from starter) cause an off balance condition which would cause vibration?

Thanks.

MinnFlyer

My Feedback: (4)

If all else fails, you can cut a hatch in the top of the fuse right behind the firewall to access the tank.
I doubt that the spinner grooves could make it vibrate. But the fact that it has a vibration doesn't sound good. Try this, take out the glow plug and spin the prop with your finger. Does it spin smoothly? Or do you feel a snug spot? It may be snug at the pistons uppermost point, but it should not happen anywhere else in the rotation. If it does, you could have a bent crankshaft.

How much impact did the engine take when it hit the tree?

hoppy

There are no rough spots when I spin the prop. I thing the impact was more to the wing. A big chunk about 8 in long by 4 inches deep. The prop was broken though so it did hit something.

The wing was hit so hard that the fuselage broke underneath the rear of the wing. It broke only on one side (a crack through the rear firewall if that's what it's called). I glued it back and it seems strong enough. Could that be causing the vibration?

mscic-RCU

My Feedback: (6)

You should be able to pull the tank out of the plane, it just slides in on a superstar. Check and make sure that your clunk is in the back of the tank, no cuts or holes in your fuel tank. If you are sure that your prop is balanced, you might have bent the crank when you hit the tree. Also check around the carb for cracks in the case. It could be sucking air through the case. good luck

mscic-RCU

My Feedback: (6)

I meant cuts or holes in your fuel line, but could check tank also.

hoppy

mscic,

I don't think I can pull the tank out the firewall is glued in. Unless it comes out through the front when the engine is removed.

Blackie

Shot in the dark.

Tony did you say that you did! break the prop? if so did you replace it with a new prop? and again if so what type of prop did you go back with?

If you had a wooden or an APC composite prop and switched over to a master air screw then you will get a little vibration as the MA's will cause a small bit of vibration.

You will have to try and break the tank loose by any means possible. The tank is entered and exited through the fuse. Maybe using a razor/pocket knife might help. Its best that you check all of the fuel lines and the tank as well.

Other things to look for in the fuel line behind the needle valve feeding the carb, are you seeing air bubbles when you tilt the plane up. This will tell you if you are sucking air. If you are seeing bubbles in the line as it lies flat then you might have a hole in the line.

Again it is also a possibility that the shaft could be bent. If being that the case then I wouldn't worry as that engine is easily replaced at a small cost, you might even option for the OS FX series.

Randy

hoppy

Randy,

I replaced the prop with the same type of wooden prop that it had, (topflite or something like that). I did balance it...

I see air bubbles in the line as I tilt the plane up. You said that means it's sucking air so does that mean there is probably a problem with the fuel tank?

Thanks for the help.

Blackie

Good ok now we are getting somewhere. Yes you definitely have a problem in the tank/line area. If you can get to the tubing try that first replace the feed line and might as well replace the vent line as well with some medium tubing. Give it another try and if that does not help then I am afraid that your tank will need attention.

Another question do you see fuel on the balsa inside the fuse itself under the tank?

hoppy

blackie,

I can't see under the tank the blasted firewall is in the way. (not at the plane now though). Will I have to cut the firewall out to get to it?

If I just replace the lines, by vent line do you mean the one that goes to the muffler? I will have to pull the engine correct? (so I can get the lines on the tank)

rcflier_gi

My Feedback: (2)

The tank should come in and out through the back (the access area where the wing usually rests). You shouldn't have to cut the firewall to remove the tank.

Blackie

rcflier is right, the tank should come out through the fuse Just remove the wing and try to get a hold on the tank through there. Remember to disconnect the lines from the muffler and the needle valve. The vent line is the line that goes to the muffler.

hoppy

I'll try but the firewall has a small round hole in it and the tank is square shaped and I'm pretty sure it's bigger than the hole.

Thanks .

rcflier_gi

My Feedback: (2)

Don't try to pull the tank through the firewall. It comes out through the back. Pull it from behind, toward the tail of the plane. Normally the receiver and battery pack are behind the tank so you may need to remove them first. But again the tank comes out through the back NOT through the firewall.