Topic: Piston stuck

[Ramirez]

Ah well, things were going so well and then;
I was fitting the barrels to my 500 four and got 2 & 3 pistons in, rings and scrapers into the barrel, then turned the crank and got 1 & 4 in. Dropped the barrel to leave about an inch gap to the crankcase and fitted the cam chain tensioner and guide. I then tried to lower the barrels onto the crankcase but it wouldn't budge.
Piston 3 is stuck in the barrel!
I've lifted the barrels again and got 1 & 4 out, and the cam chain guide and tensioner out, piston 2 is loose in the barrel but piston 3 won't move. I can't get it to go in or come out of the barrel. I've tried lifting it, tapping it with a mallet, putting wood on Pistons 1 & 4 and turning the crank but to no avail.
I've come in the house now for a cuppa and a think.........
Any ideas anyone?

[qside]

Do you think you broke and wedged a ring? Can you get a mirror under the piston and see if anything is stuck?

[Ramirez]

Thanks qside, I'll go take a look now.

[Ramirez]

Hmm, I can't see anything but it does feel like that, or something else in the barrel. I did make sure it was all clean before I started so a damaged ring sounds favourite to me. 

[qside]

i am worried that you may damage your cylinder if you force it. Try to heat the cylinder and maybe it will expand enough to free up the piston.

[rb550four]

My guess would be a flipped up wiper ring  or wrist pin clip wasn't all the way in. Either one will give you the same problem. Luckily you know about it now.
 Unfortunately, There is no way real to know if you will be limiting further damage as you don't know how much damage is there now . Sounds like a crapshoot. You'll know when it comes out.
 If it were me , I would hang the engine from the jugs with ratchet straps an inch or two off the surface( table or floor) on the front engine mounts with a 2x4 under the rear mounts and let the weight of the motor do the work. You may decide to tap the piston out the cylinder with a block of wood  but still leave the motor hang let the weight do the work. Good luck.

[Ramirez]

Thanks guys. I've had it soaking in plus gas overnight and I'll have another go at it this morning.
I like the idea of using the weight of the engine to move the piston. All the ideas I had so far involved mallets and bottle jacks! 
I'll let you know how I get on.

[Ramirez]

Yep! Wiper ring. Luckily there is only a slight mark right at the base of the barrel.
I'm gonna get the barrels honed and a new set of rings......and then wreck something else 
Thanks for your help guys.