How do I compress the ring on the piston to get the piston back in the cylinder?
Kurt
Engine Assembly
Stuka Stunt Main Forum · 11 of 11 known posts recovered
Cut thin strip copper about one inch tall and two inches long.
Wrap copper strip around piston and ring. Put hose clamp
around copper strip. Tighten clamp a little at a time. Put piston
and clamp on top of sleave. Push down with wood block.
Wrap copper strip around piston and ring. Put hose clamp
around copper strip. Tighten clamp a little at a time. Put piston
and clamp on top of sleave. Push down with wood block.
I've only had a few ringed engines, but never had to use anything but fingertips/nails. A strip of plastic from a 2 liter pop bottle, or aluminum from a can, and an electrical zip-tie should work fine. Steve
The little McCoy rings are delicate, just do as advised, and be careful. Try and offset the ring gaps 180 degrees or somewhere in the area as you put the piston back in the liner.
JAK
"It'll probably feel real good again, once it quits hurting".
Installing pistons with rings in sleeves; the way everybody has suggested is correct except model engines, the piston of the engine should always go in from the bottom of the sleeve unlike automotive engines but more like motorcycle engines. Most model engines you can use your finger nails to compress the ring however another little trick to use a flat shoelace pull tight to compress the ring while you slide the cylinder or the sleeve over the piston. Also be careful of ring locating pins in early engines and use plenty of oil. As a matter of fact, I just rebuilt one of those beautiful Dooling 29s; also watch your ring and gap, you must have around .003 this can vary from engine to engine.
As a matter of fact, fitting the piston to the liner on a lapped engine should also be done from the bottom of the sleeve up; if the piston fits from the top down I would have to say this is a dead combination.
As a matter of fact, fitting the piston to the liner on a lapped engine should also be done from the bottom of the sleeve up; if the piston fits from the top down I would have to say this is a dead combination.
LAST EDITED ON Aug-28-01 AT 08:04 PM (CDT)
I forgetted to say this! You are absolutely correct, it needs to go in from the bottom of the sleeve. It's like a motorcycle or VW, or other aircooled engine. Put the piston/rod on the crank in the case, and then slide the sleeve down over the piston into the case. Ringed engines are different than lapped in the final fit, but in either case, if you can easily put the piston in through the top, you have a real bummer of a fit, and likely the puppy won't start at all, much less run well.
JAK
"It'll probably feel real good again, once it quits hurting".
OK, so if the piston should go in from the bottom of the cylinder then I have to remove it from the case. Any suggestions on how I should procede with that? The cylinder liner seems to be press fit in the case, is that correct?. After the cylinder liner is out then how do I get it back in?
Kurt
They just slide into the case, they aren't really "pressed in". If it is clean, it should come out easily. One old trick is to use a popsicle stick or other flat piece of wood (hard balsa will work too) inserted into the exhaust, with the piston down, then turn the crank over carefully until the piston contacts it, and you can jack the liner up out of the case enough to get your fingers on it. If it is really stuck, you need to soak it in the crockpot or an ultra sonic cleaner first. Above all don't force or pry on anything!
Putting it back together, the liner is just slid down over the piston enough to get the rings in the bore. Put the rod into the case and and then push the liner down into the case again, once the rear valve is lined up correct and all.
Putting it back together, the liner is just slid down over the piston enough to get the rings in the bore. Put the rod into the case and and then push the liner down into the case again, once the rear valve is lined up correct and all.
JAK
"It'll probably feel real good again, once it quits hurting".
Jake, you are right! Heat is the secret to dissamble and assemble engines; we have aluminum cases with steel parts fitting into them, it's very simple aluminum when heated expands more than steel, So when dissassembling an engine you can use a heat gun, propane torch and I have even used boiling hot water. Any of these methods will work very nicely; older engines seem to be more of a problem such as McCoy 60, there cylinders were fitted far too tight. This is an old thery I won't go into right now. If you are a newcomer I highly recommend the book "ALL ABOUT ENGINES" by Harry Highley, this book covers all types of engines with lots of tricks and is well worth the price.
I take it the reason for assembling the piston into the cylinder from the bottom is because of a slight taper to the cylinder? Is that correct? I didn't think these old engines with rings were tapered like the newer ABC types. If they aren't tapered then what difference does it make if the piston goes in the cylinder from the top or bottom?
Kurt
ALL of them are tapered, to some degree. The only place you get a tight compression seal is approaching TDC.
If you have a ringed motor, put a little light oil in the exhaust, and run the piston up, you'll see compression leaking somewhat until you hit that point. Ringed engines are different than lapped it is true, but the piston should go in through the bottom, as typical of almost all aircooled motor practice.
If you have a ringed motor, put a little light oil in the exhaust, and run the piston up, you'll see compression leaking somewhat until you hit that point. Ringed engines are different than lapped it is true, but the piston should go in through the bottom, as typical of almost all aircooled motor practice.
JAK