Please Help: Reassembly Gone Ary

[Mgriz]

So today was supposed to be a good day, but it went about as bad as it could go. I started to assemble my bike (Rebuilt head, honed cylinders, new rings) with a friend. We installed the new rings, positioned the gaps, etc. After oiling down the barrels and the pistons the cylinders went on relatively easily. That is until we got the #1+4 pistons in. The rings went in easy but when the pistons goat about 3/4 of the way in the cylinders no longer wanted to slide down into place. We tapped a little with a rubber mallet and it moved a little but I decided it would be best to pull the cylinders off, check for burrs or gunk, and start over. Unfourtunatlety it turns out that the #1 piston is stuck and I can't get the cylinders off. When I crank the engine all the other pistons slide easily except #1. I have tried pulling on it, smacking it with the mallet... everything. It will not budge no matter what I do, I have no idea what could have happened to make it this stuck but Im all out of ideas for getting the cylinders off. Any help would be greatly apprechiated.

[SqDancerLynn1]

I would bet you broke a oil ring & its jamed between the cylinder I would try supporting the cylinder base with some 2x2s & use a block of wood & large hammer to drive the piston down

[flyingace]

Possible the ring-end gap was inadequate, and now the ring is jammed in the barrel. Did you verify enough gap? If you did, then I would go along with Lynns idea of a broken ring.

All I can think of to do is try to squirt some heavy oil up underneath the jammed ring and hammer on it from above. Hopefully, the area of the scoring will not be in area of ring travel.

[Mgriz]

Possible the ring-end gap was inadequate, and now the ring is jammed in the barrel. Did you verify enough gap? If you did, then I would go along with Lynns idea of a broken ring.

All I can think of to do is try to squirt some heavy oil up underneath the jammed ring and hammer on it from above. Hopefully, the area of the scoring will not be in area of ring travel.

...No I didn't bother verifying the ring end gap, b/c I assumed they would be fine. I guess you know what happens when you assume... I picked up some 2x2s and Ill try and free it up as soon as I get some time. Thanks for your responses. So what happens of the scoring is pretty bad... Re-hone or would it probably need to be bored? That would stink... but maybe an excuse to go w/ a big bore kit. Thanks again.

[flyingace]

It just depends on where the damage occurs and how bad it is. If it's a ring-end gap problem, the damage is probably higher up the cylinder wall than if it's a broken oil control ring. If the damage is below the depth of normal ring travel (stroke length) there is no reason to worry.

I would not assume an end-gap problem. You are correct that they should be OK unless they are over-sized. It's just that it's easy to get the wrong ring size, so you always have to measure. I would think a piston jammed with a too-large ring would not be so hard to punch out. Maybe it's something else...

Anyway, good luck.

[hungryman]

Just a reminder - always check everything first and never force anything in a rebuild. Take your time, especially if this is your first rebuild.

I've rebuilt more engines than I care to count and I ALWAYS check the details - sometimes twice. It will definetly save your hiney.

One more tip - there is no such thing as too clean - parts, hands, and tools.

As for the ring end gap - if they don't have clearance they can wedge in there pretty tight. There shouldn't be any damage if it's the gap. If it's an oil control ring that wasn't installed properly then you could have scored the piston. If it's not bad use some fine emory cloth on it to remove the burr.

[DaveDanger]

ring end gap, ring end gap, ring end gap. I'll bet my last buffalo nickel that the ring has seized in that cylinder. Do place wood strips under the cylinder barrel to support it and drive that piston back down with steady hammer taps against a driver (I like to use a thick walled piece of schedule 80 PVC plumbing pipe as close to piston diameter as possible, with a piece of wood on top of that). Try to focus the hammer blows against the edges of the piston and not in the center. Once you've gotten the piston back out, remove the rings and check them ALL in the cylinder by placing them one at a time into the cylinder, and using the piston, push the rings slowly into the cylinder, frequently check the end gap for a minimum dimension called out in the service manual. Typically, a used cylinder (even if honed) will have a small amount of "choke" in it, or taper that grows tighter towards the head area. That's where it's the most critical for the ring end gap to be correct. Obviously, if the ring begins to bind while sliding into the cylinder, the gap has disappeared and you need to remove it and grind the gap larger. A small amount at a time. Recheck frequently.

[silverhorse47]

I would freeze a paper cup full of water and set it on top of the stuck piston for a while. Consider simultaneously heating heat the block slowly with a propane torch...carefully though. Dry ice would be ideal.
S.

[flyingace]

Silverhorse, no dis meant but I can't go along with the heating/freezing idea. The piston isn't stuck, the ring is jammed into the bore. The ring is the only part touching the barrel, so it will heat up and expand while only the piston 'shrinks'.

[silverhorse47]

Perhaps. But it is the ring grooves that guide the rings into the cylinder, so there is contact between the piston itself and the ring. In any case, it might work to give the tiny bit of clearance necessary to avoid gouging the cylinder...no harm in trying, and nice gains if it works.

S.

[Mgriz]

Thanks for all your replies, I got the cylinders off w/ a big hammer and some 2x2s! It was an oil control ring that was bent and jammed between the cylinder and the piston. Now I have ordered another set of rings but obviously I'd like to avoid this mess again...

So I'll tripple check the ring gaps but my service manual doesn't say anything about the oil control rings. I figured they weren't as tight a fit as the piston rings. Maybe I just didn't oil the rings/barrels enough and that ring didn't want to slide... Any thoughts on this? Again thanks for your help.

[flyingace]

That's a much better scenario than the compression ring gap too small. I doubt if it had anything to do with the end-gap, but more the oil control ring slipped out while installing.

I'll give you my proceedure on how to install rings into the cylinders. Others may have a better way, but this worked for me.

1. Buy 2 4" inch hose clamps. Make sure they are wide enough to cover all the rings when you cinch them down on the piston.
2. Place the 2X4s (flat side) between the cylinders and the block.
3. Start with #2&3 pistons. Clamp the clamps tight on the rings and move them up into place just above the cylinder bores.
4. Hand crank the engine to slightly lift the pistons into the cylinder, then loosen the clamps slightly. This will allow the pistons to move up into the cylinder while you tap the cylinder down gently with a rubber mallot.
5. Once #2&3 are in, move the clamps to #1&4 and repeat process.

They should go right in.

Good Luck.

[Mgriz]

Great, that sounds easy enough. I'll give it a try as soon as the rings come in. Thanks again!