Troubles fitting a ringed piston into a sleeve

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EvhCo

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Hey guys! I'm not sure if any of you can help me, since I haven't seen any gas guzzlers topics around here, but it's my last bet.
I took apart a second-hand 58cc petrol engine I bought a while ago. It worked good, and I wanted to make sure everything was looking good, too (it's a second-hand after all).

Fast forward 5 seconds, it's time to put it back. I heat the cylinder with a butane mini-burner, make sure the rings are not over the anti rotation pin, and put the cylinder around it.
So far everything good. The rings form a tight fit nicely. However, I soon realize I can't push the sleeve much past that. If I get the piston to bottom dead position (in such way that the head sits normally on the block), and then try to spin the flywheel, the piston seems to be hitting something solid half-way through the stroke. It essentially sounds as if something in the middle of the cylinder is blocking the piston.

I've lost all my tries, and Uncle Google isn't of any help no more. Do any of you have any ideas? Thanks.

Here's a pic of the interior of the head:
CDmAJjc.jpg

Ignore my nails. I've haven't left the house in weeks. :vamp:
 
did you remove the piston ?? some pistons only go one way ..is there an arrow on the top of it ? ... if yes ..it should point to the exhaust port ..

also , make sure its well lubricated when you try to put the sleeve back
 
Hi. No, the piston was untouched, and yes, the arrow was pointing towards the exhaust port the whole time. The muffler's size makes it impossible for me to install it any other way.

Yes, I lubricated it as well, but it rather feels like there's something in the way of the actual piston or something. Maybe the ring is hitting a piece of the sleeve or whatever, it only started doing this after I took it apart.
 
can you see through the ports when you slide the sleeve on the piston ? make sure the rings dont snag on the edge of the ports ...you might need to push the rings in a little ...

i had that happen to me before
 
FIXED!!!
One of the ports apparently peeked inside the cylinder for whatever reason. I hit them a bit with a pair of pliers, and after heating it, the piston slid in like new.
Thanks for the help, Macguyver! :)
 
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