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bob27s -> RE: SJ 60LX Glow plug=candy (1/28/2008 10:31:23 PM)
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thanks for writing.....
sorry for the delay.
First off....
You are not following the break-in instructions. That is absolutely critical. This engine is a whole other level of performance than any other sport engine out there.
This is a quote from one of the instruction/caution sheets that comes with the 60LX engine...
"CAUTION!!!!!!!!
THIS ENGINE (___.60LX____) IS EQUIPPED WITH A DIFFERENT MUFFLER OR TUNING SYSTEM THAN DESCRIBED IN YOUR INSTRUCTIONS. PROPELLER RECOMMENDATIONS HAVE BEEN DISCUSSED WITH JETT ENGINEERING. USE EXTREME CAUTION WHEN DEVIATING FROM THESE RECOMMENDATIONS. THE USE OF TOO LARGE A PROPELLER CAN LEAD TO LEAN RUNNING AND ENGINE DAMAGE.
THESE ARE SOME SUGGESTIONS:
APC
10X6
9X8
9X9
PROPELLERS SHOULD BE MATCHED TO RPM. THIS ENGINE LIKES TO TURN MORE THAN 17000 (PEAK, NOT LAUNCH), SO SIZE YOUR PROPS A LITTLE SMALLER THAN USUAL AND LET THE ENGINE TURN!!!! "
Break-in prop for a 60LX can not be a 10x6 prop. You want to use a prop one inch less diameter, or one.two "pitch" sizes lower in size for break-in. Chances are the engine is not getting to proper RPM and is ended up lean/hot. The 10x6 prop is the largest size recommended for the engine, and is suitable only after complete break-in and perhaps a bit of run time.
For break-in, use a standard blade APC 9x6, 9x7, racing type 8.75x8, 8.5x7.25 or an APC 10x6 prop clipped to 8.5" diameter and balanced.
Mount the engine on a test stand. Start with the engine rich (5 turns open). Using any of the props noted above. Start the engine at full throttle, lean it out so it is in stable but rich 2c, and remove the glow driver. Then lean it a bit more ... take the engine to 18,000 rpm and let it run there. Do not go to peak rpm with that prop. It will be running a bit rich at that rpm with the light prop load. That is what you want. Run it like that at least 20 minutes.
On the following tank, replace the prop with a flight prop - I suggest a 9x8 or your 10x6 prop. Take the engine to full throttle, lean it to peak rpm (find it very briefly, then back off immediately) then back off 800-900 rpm. Note the rpm, approximate needle setting - that is where you want to set it for first flight. For flight, you want to launch this engine at least 800 rpm rich down from peak rpm.
Do not use an OS #8 plug. It is too cold for the 60LX engine when it comes to throttle response... but it is ok for the top end. McCoy 56, Merlin HD Hot (supplied with engine), Rossi 2 or 3, Enya 3, OS A3 are decent choices. I personally prefer the K&B 1-L and K&B HP plugs. The OS F plug is good too, after initial break-in.
The engine blows plugs for one main reason - a lean run. Also if it is getting hot from being overloaded, it can create its own lean condition and toast the plug. Trying a different plug will not prevent a blown plug.
Double check the fuel system on the test stand. Be sure it is mounted on a foam pad so it does not create foam or air bubbles.
Same goes for the airframe - make sure it is 100% foam isolated, or are alternately using a bubble-free fuel system.
The 10x6 prop is the very largest prop you want to use on this engine. Only try it after break-in, and preferably after a test flight or two.
If you need some help along the way, drop me a note. I'm not all that far from you it appears.
Bob
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