Hi,
     
I was flying my new Akromaster with a McCoy 19.  The head, including the piston sleeve came off.  I can't get it to go back on.  I can get the piston to go about half way into the sleeve.  Should I grease it more or force it?  Could it be badly damage.  I see a little bit of wear on the piston sleeve.

Thanks for your help

The problem with McCoy head screws is that they are soft metal and there is about 1 screwdriver that is really good to use on them or they will deform instantly and never tighten correctly after that. Replace them with 4/40 X1 inch socket heads and the other 3 are 4/40 X1/4.  The back plate screws are also 4/40x1/4 inch screws. You should notice a definite improvement in the running when you eliminate the leaks around the head, back plate and cylinder base.

  Waking up and drinking coffee and your
headline made me laugh and start choking.

Obviously you intentionally added the word
"Motor", but....

"Head Came Off in Flight" 

...would have drawn a few more hits.

Thanks for the morning smile! 

Like Brett, I suspect that there has been a fair bit of damage done when the engine disintegrated. If you are a normal flyer, then just get another engine. If it were me, I would fix it, spending god knows how many hours making new bits for an engine that only costs a few dollars . This hobby has all sort of people!
Totally off topic, I was running in a Mills 1.3 made in India (and pretty grim are most of them!). There was a pop and bang and the engine stopped with the noise of a few bits dropping from the ceiling!. The screw on aluminium fins had fractured at the top fin and the contra piston, compression screw, and the top fin of the jacket had made a dent in the ceiling. They don't make them like that anymore!

Andrew.

It may well have bent the rod when the cyl. blew off. That would explain the hard to put it back together and the binding.

Allen,
In my opinion, what worked for me, this might work, it is my best guess (disclaimer complete). You should disassemble the whole motor. Clean off any dirt and visually inspect the piston and connecting rod looking for signs of a bent rod or if the wrist pin is jammed or lost an end cap.

Next remove the glow plug from the head and put some light oil in the sleeve. Align the piston to its normal running position (baffle toward the intake port) and slide it in, it should go in smoothly without binding. If it does put the engine back together and if it now binds or jams it is a bent connecting rod.

At this point it is best to get a new rod, however that might be difficult to find (look on eBay, might get lucky). Other option, since at this point the motor is trashed, remove the piston and connecting rod from the motor, take out the crank shaft then take the piston and rod your left hand (if you are right handed, revise this if you are left handed), insert the crank pin into the bottom of the rod, put your thumb under were the rod connects to the crankshaft (counter weight at the top), wrap your fingers around the shaft and give it a quick downward tweak. Not real hard just so you feel resistance.

Put the motor back together and see if it turns smoothly, if not, do it again maybe a little harder. You will be surprised, you get a feel for how much to tweak and after a few shots and you can get it straight. I did this on an old Enya that I bent the rod using a starter and it worked for me (your results may differ, is statement is not intended to cure or prevent anything from breaking or not working). Another option is to remove the connecting rod and put it on a flat hard surface with the bent side up then use a small ball peen hammer to tap at the bend location. Then reassemble and see if it is smooth, repeat as needed to get it straight.

Best,          DennsT

I would heat the case in the oven or with a heat gun for a bit, maybe 150-200 degrees, then put the other part in the freezer for a bit.  Then slide together and reconnect the rod.  And HOPE for the best.