Hi All,
I have a T-Rex 600 Nitro with an Align/OS Hyper 50 in it.
Its had 6 or so tanks through it and has run like a clock. Yesterday, It leaned out and stalled. I managed an Auto and landed safely. The motor was hot but not seized. After it cooled I couldn''t start it again.

Check list:
Changed Glow plug 3 times
compression seems ok
Clean filters and clunks
fuel lines ok Engine is getting fuel
removed and cleaned engine and carb 3 times
Just won''t go! not even a kick

How do I tell if the ring is damaged? The piston seems a bit discolored and has some scratches on it.
Can this cause the engine not to start?

cheers
CJ

If you have good compression, a good glow plug, and good fuel, a model engine WILL fire. If it won''t fire, then you have to do some checking. First off, glow plugs are considered consumable items. They do wear out. In harsher environments, such as helis, they don''t last as long as in most airplane models. Try a new plug first.

If the engine still won''t fire, and you have a good glow plug battery, then make sure the engine is getting the proper amount of fuel. Too much or too little will prevent firing. One way to check is to start out with the engine dry of fuel. Remove the glow plug and put in a few drops of fuel. Spin the engine over a bit and then attach the starter battery to the plug and see if the engine will fire. If it still won''t fire, then compression is the likely culprit.

Ringed engines will lose compression if they''ve had an overheat, if they''ve had the ring break, or if foreign matter has severely scored the piston, ring, and liner. Only disassembly will help you find that.

An engine can have a good "feel" when turned over by hand, but still lack enough compression to fire a proper fuel mixture.

If you put the engine on a test stand with an airplane propeller, you should be able to diagnose what may be wrong.

HI Bax,
Tried 3 new plugs, so I think its not the glow.
I dis assembled the motor and the piston is quite scratched. We do have a dusty field and there was quite a bit of muck in the engine and carb.
As you said, the comp feels ok by hand but it might not be enough.
Perhaps I''ll change the piston.

Cheers
Carl

You were right Bax,
It was the piston and ring. I don't know how it happened, perhaps it sicked in a heap of dust . I might try using a filter!

Thanks
CJ