Engine help please
 

Hello. I have about 10 flights on a Kadet Senior with an OS 40 LA. The engine has run beautifully the entire time. My instructor suggested I run her a bit rich for awhile. My last two trips to the field have resulted in 4 "glider" landings. She starts fine, runs ok, and then just quits. She doesn't lean out or sputter, just runs well, then dies. I watched it for a while and did notice a bubble or two. I changed glow plugs and that didn't seem to help.

I'm thinking the fuel went bad, some suggested vibration is causing foaming. I thought about going to a smaller tank (8 oz) to get more foam around it. It's not set too rich I don' think?

I'm getting frustrated and any advice would be appreciated. Thank you.

RE: Engine help please
 

Sounds like you have some junk in your carb. Disconnect the fuel line going in to you carb. Connect the fill line from your fuel pump the the carb. Remove the needle valve from the carb. Complete close the throttle. Now pump a little bit of fuel into the carb to flush out any debris. Put it all back together and see if that helps<div>
</div><div>Ken</div>

RE: Engine help please
 

Will do. Thanks Ken

RE: Engine help please
 

There's no need to run the engine rich once it's broken in. 300-400 rpm rich of peak on the top and set for good transitions on the bottom will give you a good performing, reliable engine.

RE: Engine help please
 

I don't know how you store your fuel but the chances of it going bad are pretty slim. Manufactures started using anti foaming agents in there fuel and you can't make it foam. Several years ago foaming was a problem, not so today. If it isn't junk in the carb as Ken mentioned then it wa probably a tune issue. LAs break in very quick and don't require a lot of break in. As the Jester mentioned, about 400 rpm below max.

RE: Engine help please
 

Is this a new engine or a used one? <div>I had a very similar problem with the same engine, which was caused by an air leak. The engine was heavily used and was picked up for free at a yard sale, however, so maybe that had more to do with it....</div><div>
</div><div>Does the engine idle well? </div><div>This could give a hint as to where the problem originates from.</div><div>
</div><div>
</div>

RE: Engine help please
 

Good point. The 4 head screws in the LAs tend to vibrate loose when new. When I bought a new one I pulled the head screws and added a driop of locktite.

RE: Engine help please
 

This filter will help avoiding the foaming or bubbling and the junk accumulation in the needle:

http://www3.towerhobbies.com/cgi-bin...&I=LXD741&P=RF

For this engine, the little air intake hole at front of the carb stack get clogged with little particles (like grass seeds) some times, messing up the low end adjustment.

RE: Engine help please
 

Wagon1,
How long did it run before the engine quit when the problem started?. Did you refill it after each flight when it quit in the air? And then did it run the same amount of time before it quit? The answers to these questions might help point to an area to check.

RE: Engine help please
 

Hi skoda. Interesting. Yes, I did refill it after each flight. It seemed to run about 3 or 4 minutes then it would quit. I would land, refill, restart (always started right up), then 3 or 4 minutes later it would quit. I was not always back at idle, sometimes it quit at 1/2 throttle. I bought a smaller tank (8 oz) yesterday. I figured I could get more foam around it than the 10 oz that's in there now?

RE: Engine help please
 

This is just a thought,but maybe you have the vent and fuel lines crossed. dennis

RE: Engine help please
 

G'day

Ah the Kadet Senior. My favourite plane for just floating around. (Mine has a Saito 56).

Anyway, it is also possible that the clunk line or even the clunk have fallen off inside the tank. I had exactly this problem recently with one of my GP big Stick 40s.

I'd be looking inside the tank. I would also not be putting a very large tank the the plane. Six to 8 oz should be fine. The LA 40 is going to provide plenty of Kadet flying power and is not going to use a great deal of fuel.

I used to fly one with an early OS FS 40 four stroke. It had no power and take offs were long and low but it always got there. It would then struggle up to about 100 feet and then putter round on half power for ages. Loops were interesting and required a small dive first. The FS 40 probably had the power of a good 25.

Enjoy.

Mike in Oz.

RE: Engine help please
 

After seeing the rest of the thread I'd give double odds that the clunk line has fallen off in the tank. If an engine will start and run right on the test stand, then the engine is fine. They don't just suddenly get wrong if they start out right. The only way your condition could be engine related is if the engine is overheating, usually in a cowl. The problem has to be in the tank or lines.

RE: Engine help please
 

also check for a possible leak in the pickup line inside the tank. if the fuel level is higher then the pin ***** in an inside fuel line then fuel flows easily to engine but if the hole is exposed to air in the tank then the engine will run lean or stall. you then fill the tank level higher then the pinhole leak and the engine works great again

RE: Engine help please
 

Balance prop, stuck clunk in top of tank instead of bottom, pin hole in pick up line. OS makes great motors. +1 on on the motro screw check.

RE: Engine help please
 

All good clues to investigate above.

Just in case the engine stops only at idle:

http://www.rcuniverse.com/forum/m_88...tm.htm#8843543

RE: Engine help please
 

**UPDATE** I found that one of the backplate screws (the one that holds the needle valve bracket) was loose. I thought I found the problem but she did the same thing at the field. One of the guys (THANK YOU ROBERT!!) spent over an hour with me trying to get her going. He narrowed it down to the small air needle in front of the carb. We tried everything!! He even tried a different prop and 4 stroke glow plug. It's much better, but still dies at idle.

By the way. This is why I love this hobby. You guys have spent time helping me out, and the guy at the field cooked in the Florida sun helping me out when he could have been flying.

RE: Engine help please
 

Start the engine up, rev it to full throttle for 10-20 seconds, then bring it back to idle.

Then pinch off the fuel line and start counting the seconds until the engine dies.

Does it?

- Die IMMEDIATELY when pinched?
- Continues to run for a few seconds, speeds up, then dies?
- Continues to run for a long time, finally speeds up, then dies?
- Doesn't seem to care the line is pinched off, just continues to run?

Please let us know.

RE: Engine help please
 

When pinched at idle she will run about 2 seconds then fall off and stall. It does the same thing when I lift the nose up at idle. Also will run at medium rpm for a minute or so, then just die. Doesn't lean out or sputter, just dies.

I appreciate all the links and advice. I'm going to try a new carb. The are $20 and still available at Tower. I'm going to chock it up to voodoo and move on. If the carb doesn't work I'll get a new engine.

Thanks again guys!

RE: Engine help please
 

there probably isnt anything wrong with the engine, it DID run great before, 99% of the time it a fuel problem. among many other things to check, fuel tank, and lines, junk in the carb, etc....air could be leaking around the needle valve too. remove the needle valve and push a 3/16" long peice of fuel line over past the threads, install the valve and make sure that little peice of line covers the area that could suck air into, the original o-ring usualy leaks after a while

RE: Engine help please
 

Probably not the issue here but I've had problems with a new Magnum XLS 46 the last 2 times I went flying. It was still in break in stage so running rich, became very hard to start (I no longer have an electric starter, if it won't start by hand, I don't want it), ran great for about 5 minutes in the air at full throttle then seemed to go VERY lean and unless I cut power would die. I never had a Magnum before and was about to swear to not have this one very long. I've been in the hobby since 1972 and there have been very few 2 stroke engines I couldn't tune. This was back when Fox was most popular, then probably Enya, and if you were in the "elite" group of pattern fliers you probably had a Super Tiger with a tuned pipe. But I digress, when I was just about mad enough to turn the engine into little pieces, I was in the process of refueling and trying to "tweek" it again, and found the muffler to be slightly loose so I tightened it up of course, guess what, it ran like a charm!!! Of course the adjustments I had been making had put it on the super rich side but easy to correct. before the day was over (yesterday) it was starting and running like a dream and again starts with one or two flips. Guess I'll keep it now ;-)
Dan

RE: Engine help please
 

You never said if you tried new fuel. In the past two years, I have seen fuel go "bad". Its very frustrating until you recognize it. My nephew had this problem at the beginning of the season. The fuel he had stored all winter (not an airtight bottle) had probably absorbed too much water. He would fuel the plane, get the engine running, take off, and then a few minutes into the flight - deadstick. He just borrowed a tank of fuel from another flier, and the plane flew beautifully for the entire tank. Its easy to rule out.

I personally don't like the four stroke glow plugs on a two stroke engine. The plugs run so hot that the engine timing ends up early, and it just ends up wasting fuel.

There's nothing to go wrong with the LA carburetors. If the fuel passages are open, they're pretty much bullet proof. But it doesn't take much to block a fuel passage. A small piece of plastic from the tank (the size of the head of a needle is huge) is often all it takes.

The airbleed screw should start with the air bleed hole 1/2 blocked, and then adjust from there. If the end of the airbleed screw has been damaged, that can screw things up (sorry about the pun) as well. A small piece of dirt or grass in the hole will drive you crazy chasing the tuning.

Finally, take the tank out and inspect the internal lines very closely. A small crack or hole in the fuel line will allow air to be drawn in, cause the engine to go lean, and - deadstick. When you put the smaller tank in, did you replace the lines?

Brad

RE: Engine help please
 

Hi!
It's very easy! If you see bubbles in the fuel line, something is wrong! Either the clunk is loose or the fuel line /tank is leaking.

RE: Engine help please
 

sounds like your main needle is slightly too lean, when you start the engine with a full tank it is perfect, then after 3-4 min its just a tiny bit harder to draw fuel so it leans out and dies. this should also help solve your leaning out problem on the low end as well. i would back it off about 5 clicks and try again.