jbeech
Key Veteran
Location: Sanford, FL (Orlando area)
| You guys are giving Top End too much grief. The top of the piston actually shows build up from running conservatively rich, not lean. However, the staining just beyond the flange show the head has been operating loose (for an undetermined period of time).
Folks, an engine's bolts should be re-torqued after the first few heat cycles (runs). While every two gallon expert out there will jump in to explain how you can successfuly break-in your engine in the helicopter (I agree, you can), I continue to advise against it. Why? Because on a test stand you control the variables. Witness how Top End made the statement how he couldn't get the model down in time once he realized something was wrong.
Anyway, after a gallon of fuel on the test stand (for the 50SX or Hyper, I advise an APC 9.5x6.5N for break-in), I'm quite confident of placing the engine into an environment (the helicopter) where there is significantly less likelihood of my being able to get the engine back to where I can make an adjustment quickly (i.e. from in flight).
Look, when the engine is broken-in in the model . . . how many of you take the time and effort to re-torque the backplate and carb bolts, much less remove the engine from the helicopter in order to re-torque the head bolts? What you see here are the results of breaking-in an engine in the model and then not re-torquing the bolts.
I would hazard a guess that the leaking at the head began with the third or fourth flight and continued to progressively get worse and is probably the leading contributor to the burn through of the piston. In my opinion, the carb coming loose would generally lead to the engine dieing out rather quickly - but this time there ws no margin for error.
Anyway, to repair the engine, plan on a piston, ring, rod, and while you're at it, a new rear bearing - and if it were my engine, a new front bearing too. Furthermore, I would advise replacing the bearings with synthetic cage versions which will withstand the ravages of combustion byproducts.
Finally, if you're into unfamiliar territory when it comes to a rebuild, I have written a white paper on the subject (specifically referencing the OS 50SX-H). It's available for free here . . .
http://www.audacitymodels.com/whitepapers/index.html
Kindest regards,
John Beech - GM (and janitor)
Audacity Models
AMA # 47381 |
