OS 46 LA problems
 

I have been running 10% with an OS #3 glow plug, and never had any problems. So today I go out, and bring some 15% fuel.
I take it up, and notice it doesn't really want to go to full throttle. It's not the servo because I checked that on the ground. Fly for about 5 min. at half throttle, and it dies. So I bring it down and realize that I should have re-adjusted the high speed needle with the new fuel, so I start it and go to WOT and start to set the high speed. The RPM's change a little, and then it quits. It only ran about 30-45 seconds. I figure I'll check the glow plug, and notice the head is really hot. The glow plug coil was white if that means anything? So I let it cool, and re-start with a new glow plug, got to WOT. I righen it some to try and keep the temp down, but same thing, it died and the head was really hot again.
I decide to quit, and try to get some info about what is going on before I do damage, if I haven't already.

Any ideas?

RE: OS 46 LA problems
 

I'm still pretty new to this but...

Seems like your running really lean... Keep trying to richen it up.. or
maybe you developed some air leaks?? That's about all I think I know:-(

I ran 15% from the start on my LA-46.. With no problems.. Still using the
same plug(OS#3) Engine has run great.. Well had a slight sleeve problem
when I nosed it into the ground.. But a little shade tree work and it's turning
like a slow top again:)

RE: OS 46 LA problems
 

Check your carb bolts, cyl head bolts & back-plate bolts. They tend to loosen on the LA series & produce symptoms similar to those that you are experiencing. The head gasket could also be leaking & may have a "track" burned across it.

Another possibility is dirt in the fuel delivery system. If the engine is not very responsive to needle valve adjustment, remove the needle & clean it, as well as flushing the entire system with fresh fuel.

Also check for a pin hole in the fuel clunk line or delivery line to the needle valve assembly -- it might be admitting air & causing the motor to lean out in flight.

RE: OS 46 LA problems
 

I do know that going up in nitro is the same as going up in oxygen. That's what the nitro does. When you increased the nitro, it's like turning on more oxygen on a blow torch. The flame (in the case, combustion) gets hotter. This is why your engine is getting hotter. I would think that you may need to go richer. Running the engine richer will cut back on the air, thus cutting back on oxygen coming into the engine and compensate for the oxygen (nitro) in the fuel. Your engine is now getting more oxygen from the fuel and this makes a more powerful burn in the engine. Sometimes engines get too lean and they will wear all at once resulting in a loss of compression. I hope this is not the case with your engine. Older engines with a lot of use are especially vulnerable to this. I've seen this before in 2 cycle gasoline engines. Adjust the mixture screw too lean, and they kick the bucket! I am always afraid that this will happen when I pinch the line on my airplane engine to shut it off. Notice how they speed up for a second. Four stroke engines will sometimes burn a valve when they run out of gas because they get real lean right before they stop. Again, it's like turning on the oxygen in a blow torch. How about anyone else? Have any thoughts on the subject?