bjcbs

My Feedback: (47)

During it's 15th flight, my AP .09 broke its connecting rod while in flight. I had broken it in correctly and have never run it overly lean. I was using 15% nitro fuel with 3 ozs extra caster oil per gallon. The engine had given no problems until this incident. My questions are:

1) What do you think could have caused it to happen?

2) How do I remove the piston to replace the connecting rod? The piston moves freely in the cylinder but will not come out the top when the head is removed.

Although not a power house, this engine has always started, idled and transitioned well and I would like to get it back into the air. I have been using it in a Hobby Shack School Boy.

SGC

bjcbs,
brocken rod could be caused by , hydraulic locking when starting,prop strike, over reving on a small prop or shaft run, lugging on too large a prop, flaw in the metal or any combination of these things.
Its a good thing the piston wont fit out the top of the cylinder- its not supposed too, the bore is tapered and relies on the pinch at TDC for compression seal, so chances are your piston cylinder fit is still good. To remove the piston you need to remove the cylinder from the crankcase, its probably stuck with dried castor oil , so you will need to heat the outside of the crankcase with a heatgun/hairdrier then pull out the cylinder, the piston will then drop out the bottom.
Stewart

AMB

I have 3 of them (converted to diesel) and excellant conversions. One of the 3 had low compression ( would not runas diesel) I sent it back and in one week was sent a new one no charge. You may want to check with them (Hobby people) if it was just a flat out
defect my guess is they will replace , the fact it happened in flight indicates it was , if not running lean martin