Hallo Guys, I need your help.

I am the Agent for ASP Engines in Namibia, and I have sold many. I can not remember that I have ever had an engine that I could not tune or not diagnose a problem on.
I have however on Saturday come across an ASP 52a that is making problems that I can not find.

The engine is +- 2 years old, and is installed in an Acro 50 of my flying buddy. It has run like a Race horse for the past 2 years, including Saturday morning, when it suddenly stopped.
It would start, run up to full revs and perform flawlessly for about 2 minutes, and then suddenly without warning dead-stick. As in instantly stop running at different throttle settings.
We pulled the tank, thinking that the clunk had come off, it is still attached as usual. Then we removed the Dubro fueling valve (knowing that these sometime make trouble)bypassing it with a straight piece of tubing, still it will dead-stick. Then I removed the remote needle, and set it up as needle on Carb, still it would dead-stick. I then cleaned the carb by pumping fuel through it, still dead-stick after about 2 minutes of running. Then we replaced all tubing, with no luck.

Please help me as I can't think of anything else.

The Engine is fitted with a 12X4 APC prop turning 14000 RPM full on 5% Nitro, as it has always done. Transition is smooth and instant. Fuel is 18% Klotz 100 (50% castor 50% synth) 5% Nitro rest Methanol.
Plug is either OS No. 8 or ASP No. 4, this has also been changed during the whole exercise.

I'm at wits end with this one
Please help

Strange one all right. The only thing I can think of is poor compression. Even if it seems fine now, the ring could be cracked or have a large score which shows up when the engine is hot. Does it seem to lean out or act hot before it quits? Is the compression poor right after it quits? The reason I say this is that the old fasioned lapped iron piston engines will often do this when run on synthetic fuel. The start and run fine for about a minute or two then act like they are running real lean for a minute, or worse run with poor perfomance but too fast to land the plane till the fuel runs out. They will then have almost no compression till it cools down, if you didn't ruin it in the process. The reason is that the piston will not seal with that thin oil and the blow by heats the cylinder up which expands faster than the piston, then the heat causes detonation which only makes matters worse.

Dries, I had the same problem with an ASP 52. And after I became a deadstick expert, I started to hear a strange noise before it died. It was the bearings, although they turn freely when cold they can suddenly heat cease. By the time you retrieve the plane they have become lose again and will turn freely.
Groete Piet

Hi Sport pilot,

Thanks for the advise. The engine is a ABC engine, and has lots of compression. I ran it rich about 1500 RPM of max with a thick smoke trail, I think it dies of fuel starvation, but where is the blockage?

Hi Piet,
I see some local guys giving advice.
Interesting point, I will check it out. I have listend to the engine very closely before it shuts off, and I have not managed to hear anything, but anything is possible. How much run-time on your 52 until it started doing this?

regards
Dries

Maybe the tank connections are reversed? I have done this, though it ran less than two minutes.

I think I had it for about six mounths then this happend. After I replaced the bearings I had it in a Stick for about 3 mounths then I swoped it. as far as I know it's still running.

For it to suddenly die like that, it would have to be fuel and most likely a blockage.
I had similar problems with a Super Tigre G.51 once and ended fixing the problem by removing the carby, stripping it and soaking the component pieces in Methylated Spirits (which is a cousin of methanol) I also probed the fuel nipple with some fuse wire.
That cup of meths turned yellow from the congealed "gunk" in the carby (not to mention the micro insects that had been sucked in and had died in there.) The engine ran fine after I put the carby back together.
But your problem could also be something floating around in the tank.
Is there anything resembling bits of cottonwool in it? (Caused by nitro going "off" from moisture absorbtion) This stuff turns up from time to time and will eventually get sucked into clunk and the block the fuel lines.
It may be worth removing the tank, opening it up an flushing it right out with some meths, which will also remove any moisture etc in the system.

I had the same problem that was driving me to drink. Wound up being the fuel clunk line where it attached to the brass tube. Even though I had the tank opened several times I missed the slight crack in the tubing where it flexed right at the end of outlet tube. It doesn't take much. It may not be your problem.

Gee Guys, thanks for the info. I will try all the cleaning, if that dose not work, i will proably renew the bearings.
keep em coming, there might be more.
dries

dries, Rob Bauer has a good point and it makes sense.

While the tank is full, fuel will be drawn through a crack in the fuel supply tubing inside the tank or the brass/nylon tubing that goes through the tank rubber bung.

As the level falls and the point where the crack is breaks through the liquid surface, then the engine will quickly be sucking air, not fuel. QED- It stops!!!

The fact that this happens at about the same time each flight points to exactly what Rob says.

Before you go to the lengths of stripping the carby, pull the tank out, and pull it apart. Renew all the internal tubing, including the brass or nylon tubing that passes through the bung, flush the tank out with meth, put the whole thing back together and go fly.

If that does not fix the problem, then go further up the line to the carby and looks for obstructions in the fuel supply lines/spray bar.