RE: Sundowner50 60LX
The sundowner install, expecially with the internal muffler, requires a TON of cooling air. You need exit area around and leaving the muffler location (exiting the fuselage somewhere), as well as a pretty large cooling hole on the bottom of the cowl.
Also keep in mind our caution with the LX engine it is the least user friendly of the Jett product line. It requires attention to details. Also remember, the "number of turns" on the needle means nothing. The 5 turns is just a reference starting point. Needle position varies greatly depending on the installation, prop, application.
Getting the engine lean or very hot is about the only way to really hurt it.
Lets solve the problem.
Answer a few questions just for diagnostics....
Did you put the engine on a test stand and follow the break-in proceedure? (critical - if you did not do this, you have no reference of how the engine is suppose to run and it is not fully ready to fly).
What prop are you using? (you want to be flying a fairly new engine here with a 9x7)
What is ground peak rpm you found on the break-in bench? On the aircraft?
What is the launch rpm (rich setting)
What fuel system? stock fuel tank or bubble-jett?
If you got the engine hot, the head may have come loose. The screws come loose if the engine gets VERY hot.
If that happend, and you changed the glow plug, you may have rotated the cylinder liner (sleeve). That will cause it to drop a ton of RPM for no apparent reason.
Best way to check remove the muffler, look in the exhaust port ..... ensure the sleeve is lined up in the crankcase. If not, loosen the head bolts.... rotate the head button and linder back into position (you can use the glow plug and plug wrench to turn it).
The cylinder head should not leak or drip at all. There is some fuel spray that comes from the carb and a bit from the front bearing this sometimes accumulates on the cylinder or crankcase do not confuse this for a leak.
Some basics on the setup:
- Use good 10% - 15% fuel (yours is just fine)
- Use a 9x7 prop to start with - seems to be fastest anyway. Let the engine unload
- Needle setting - find ground peak rpm (Briefly - what ever it comes in at) and back off 800-1000 rpm for flight.
- Verify that the fuel tank is 100% isolated from the airframe - foam padding all around - no stopper touching the firewall
- Make sure the muffler is not touching any structure.
- Verify your cooling air paths
- Mount the remote needle valve on the airframe - not mounted on the engine.
- Ensure the packing nut on the remote needle is snug. You want to use some effort to position the needle.
Worth noting here...
The very best diagnostic process is to start from the beginning. Install the engine back on the test stand. Run it. Get baseline information. Ensure it runs properly with the flight prop and the needle functions as expected. Get a reference needle position and reference rpm numbers. Then re-install it in the aircraft. If it overheats or runs strange once re-installed in the plane, you know the issue is with the aircraft.
Let me know on the requested setup info..... and take a look at the sleeve alignment.
Bob