I have a new OS 40fp engine {I know the Os don't make 40fp anymore but this one was never run and was still in the box.} I have ran the engine on a test stand 2 tanks of fuel then i put it on the airplane. the engine starts fine and runs great for about 4 to 5 minutes then it quits. now yesterday it quit at a vary bad time and I crashed the plane .I have about 4 8oz tanks of fuel ran in it with the engine installed on the plane. I have changed the glow plug 3 times we have worked with the idle and high speed set screwsand still can't keep the engine running. I been working with some of the guy at the club field and no one can help me out can someone here tell what the problem could be. Please help.

Does the engine have trouble at high speed, low speed, or in transition?

there's quite a few folks here that have helped me with engine tuning advice and they are very knowledgeable (opjose, greybeard, edmooreman, etc.). I would make sure to ask at least one of them directly.

If your engine runs just fine for 4 minutes (idle, transition, high speed) then quits, it sounds like a fuel delivery problem or possibly is set too lean and overheating. It'll lean out in the air. Have you checked all the basics? Can you see smoke trail in the air? Make sure you test with your tank half full on the ground. Are you getting bubbles in the lines? Have you checked all connections and performed a pressure test? Check that clunk in the tank isn't twisted forward. Is the carb significantly higher than the centerline of the tank?

Im just guessing, but is it possible that since the engine is new and hasnt been broken in, it just needs more time. This season I started running an 55AX. The first 10 flights I kept getting dead sticks(I would keep the plane close and high expecting it to quit just in case). I didnt change anything, got some fuel through it , and now the thing just wont quit.

Again Im just guessing. If whats been stated above checks out ok....What I personally would do is run say 4 or 5 tanks on the ground to break it in more then make sure your tuning is right. Try again and see what happens. Thats just what I would probably do. I would also use a tach to make sure your tuning it correctly. For some reason I cant tune my 55ax perfectly by ear. I use a tach every time and havent had a problem since the first week.

Time to check your tank and fuel delivery lines

I would agree with this 100%. Pull the tank and check your lines, both soft and the metal sections in the tank stopper, carefully from the clunk to the carb. I had a similar issue, also with a 40FP, a couple of years back. Turned out to be a small crack in the brass tube through the stopper. It would run fine until the fuel level was below the tube in the tank, then draw air, lean out and die. Drove us nuts trying to track it down. Good luck.

I had an issue like this and found a crack in the metal tube that went through the stopper

Dittos to all that has been mentioned so far but in addition you need to be aware that the FP's like the LA series has a bleeder carburator. It is not the common double needle type and it is opposite of the more conventional now double needle type.

To make the midrange leaner unlike the double needle type you need to turn the screw out not in.


John

You may be trying to run it too lean?

Hold the nose of the plane straight up with the engine full throttle before you set the plane on the ground to see if the engine still runs OK?

What size prop and what type of fuel?

I really get persnickity with tank installs just because its a rather common source of aggrivation. I have watched people spend hours fartin' around with a pour running engine that had bad fuel flow or an air leak. I retube the tank almost any time I have one out. Smooth off the tubing ends as they can cut lines. Make sure your not getting foaming from vibration as well. Bad tank installation cause lean runs . Lean runs kill RC engines.

Here is a little engine document that is PRICELESS. I have new guys copy print it out and keep it in there field box. Save the web site and share with others.

http://www.smrcc.net/Tips/Engine/2-stroke_engine.html

well we have tryed everything and now we have a burnt up engine so back to the drawning board . i guess one of those bad engines

Not sure this is the right forum but anyway here goes.

I have a O.S. .46ax that has ran fine for a couple of years. All of a sudden it wont idel and has very little compression. So, I pulled out the sleeve and checked it out. I was cleaning it when I discovered the chrome had come off the sleeve. I mean the bottom of the cleaning container was covered with thye "Stuff". I've contacted O.S. and basicly they said tough. I can buy a new sleeve and piston for anound $80. Wow, the motor only cost about $120.00. Why would I want to buy a sleeve and piston and "hope" this is all that's wrong. Seems to me this is really poor consumer relations. I've checked with my club and the internet and found this is not uncommon with this engine.

This will most likely be my last ever O.S. engine unless someone has some suggestions. I'm open for comment.

Thanks.

I have had only one engine doing what the OP is having a problem with. In my case the fuel tank is mounted way too far back in the fuse and as soon as it burns off about 1/4 of a tank of fuel there isn't enough pressure to help the fuel flow. I thought it was a cracked line in the tank so that was the first thing I looked at. The tank is fine and it's not sucking air. With the tank pulled out and taped onto the fuse closer to teh engine all is fine. That's just something else to look at.
Chrome peeling was a problem with the FX when it first hit the market. That was the number one small engine being used at my field when it came out and it was happening to pretty much all of them. OS got the word and fixed the problem. This is the first time I have heard of it happening with the AX though. I would go into the engine forum right away and talk to Bill Baxter about it, the OS service rep. I don't know if something like lean running over time would do that??After a couple of years you may be out of luck but Bill may want to see the engine and see if there was a manufracturing problem?? Let hm know the brand and type of fuel you have used too. As much info as you can give will help. As for other engines, I have tried the SK line of engines from Kangke and like them as well as OS. I have only tried the .91 though so can't say anything about there other sizes. The .91 is about $100.00 with muffler. As far as two strokes go it's a lot of bang for the buck.

G'day

It is just possible that the tank is too tall (or too low) and so as the flight progresses, the mixture becomes leaner and eventually the engine stops.

There is an easy way to find out.

1. Fill the tank to about 1/4. Start the engine and tune it for flight.

2. Now fill the tank. Start the engine again AT THE SAME TUNE. Is it running much the same as before or is running really rich?

If it is running as it was at 1/4 tank, then the tank is not the problem. If it is slobbering rich then you have a problem.

One possible cure is to use a second clunk in the tank for the vent line (which goes to the muffler) so that the two clunks are separated by about 3/8 inch and they are tied together by something like heat shrink or cable ties (loosely). This setup is called a Uniflow tank and gives a better top to bottom engine run.

There is also the extremely rare possibility that the muffler pressure connection is blocked. This would be unusual with a new engine but I had one pressure fitting that had not been drilled properly.

After writing the above, I saw your comment about a "burnt up engine". If it is "burnt up" then it has been running hot. Hot running means that either it is not getting sufficient cooling or it is being run lean or it was not ready to fly and needed more running. I think the most likely is that it was running lean possibly because of the tank problem I outlined. The engine is probably still OK. It just needs the right amount of fuel throughout its flight.

Can you show us the setup? How high is the engine relative to the tank? What fuel are you using? Prop? Plug? Muffler? All these things can affect how it runs.