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Sundowner50 60LX

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Old 08-26-2008, 10:09 AM
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heli2883
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Default Sundowner50 60LX

The motor is running real hot. I have run 4 tanks through the engine and it still runs hot. the motor is set to a richer mixture. 5 turn on the high like recomended. I had the motor over heated on my maiden flight. the plane kept loosing HP. I landed and the Glow plug was blown. Looks like it got real hot. Also after the motor cooled i started it up again and there was fuel coming out between the head and base of teh engine. I tightened down the head bolts and it seems to have really slowed it down. Only a drip now and then is all that can be seen. any suggestions? fuel 15% Byron Premium fuel 18% castrol. The engine is still running fine just seems to get hot is all. Wet finger make a sizzle on the head. Is that normal?
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Old 08-26-2008, 11:20 AM
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bob27s
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Default 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
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Old 08-26-2008, 12:07 PM
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heli2883
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Default RE: Sundowner50 60LX

Thanks bob i will start over like you staited
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Old 08-28-2008, 01:47 PM
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rmenke
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Default RE: Sundowner50 60LX

madness:

As usual, Bob gives us outstanding information based on actual use of these outstanding engines. Isolating the fuel tank, and locating the remote needle onto the airframe seems to be a absolute must with this engine, I assume due to the high rpm's. I would suggest one additional thing. We are dealing with a high performance engine of high quality here that deserves the best in care and feeding. To that end, I recommend the frequent use of a quality torque wrench on the head bolts, and pipe. I check mine before I go fly every day of use. The typical day of use generally involves two pre-race flights, and three race heats, close to around 1 hour of run time, five cycles of heat/cool. After the day, my head bolts are usually a little loose. I experienced the fuel out of the head area big time with my first 60LX, thought there was a broken line at first. Missed a race heat because I would not tighten down a hot engine head, period. My second 60LX does the same thing. A little extra care goes a long way with these engines. Have one that still runs on top that is 7 years old. Of my 5, have never had to replace a part from normal wear, and expect them to outlive me. They become cheap engines when you consider their usefull life!!. ENJOY
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