Pistons with new rings stuck in the jug

[larrynyc]

Hello,

I'm knee-deep in a top-end rebuild on a '75 XS650B. I've had a few hurdles but thanks to this forum you guys have helped me through.

Unfortunately I'm really stuck now. Literally. Background: After a successful honing job on stock cylinders within the jug, I put new stock-sized piston rings from Mike's XS. I didn't have new circlips to remove the pistons, so I kept the pistons on and lowered the jug onto them. At the opposite of top-dead-center (bottom dead center?) I used the popsicle-stick method to wedge the rings into the cylinders from below, and seated the jug down. I gave a few whacks with a rubber mallet and everything seemed fine. Until I tried to turn over the engine -- the jug was actually stuck to the pistons.

So I assumed the pistons weren't in far enough, so I turned the engine upside-down and whacked the jug upwards a couple of times with a rubber mallet. The jug moved, so I thought things were good. But it turns out the pistons are stuck even deeper.

So now I have stuck pistons -- the pistons are 1/4 up the jug I can't see the circlips at all. I can't pull the jug off because they're literally stuck and move up/down with the pistons as the crank turns.

Did I royally screw up? What's the best way to get these out? I'm at a very frustrating point. Thanks in advance.

 

[larrynyc]

Finally solved the problem. I figure I should post my process just in case someone else has the same misfortune as me:

1. I sprayed a healthy amount of PB Blaster on the pistons around the rings. It was so tight it didn't drain, but I figured it would at least creep in to the top ring.

2. I cut 2" blocks of wood to wedge between the jug and the engine, which is below top-dead-center. I purposefully didn't cut the wood all the way up at top-dead-center, to give the crank some room to head downward.

3. I cranked the engine so the pistons were moving on their way *downward.*

4. I used a *rubber handled* mallet as a punch, and whacked it with a second rubber mallet. I found that whacking in the center of the piston didn't do much; it's better to hit the piston on the edges. I went around all four corners. Go back and forth between the pistons, 8 hits on the left piston, then 8 hits on the right.

5. Keep going for a long time. It took me a good hour. It seems like the whacks do nothing but the pistons move *ever so slightly.*

Thank the stars I got those pistons out! Here are a couple pics -- you'll see the reason why they got stuck -- a nasty bent ring.

 

[peanut]

bad luck ! at least you found the problem .
For future reference never ever whack pistons into a cylinder they should slide in easy by hand pressure only . if they don't... then there is something wrong . That pretty much goes for fitting most things really .

How bad is the damage to the bore and piston groove ?

 

[member3480]

This is the reason I use hose clamps around the rings and just slowly push down and hose clamps slide down. Oil rings are soft and many times this is the outcome . You may have thought you did it right and it goes down but the bend easy. Did you do any wall damage and I might have a set of new stock oil rings if you need them.

 

[gggGary]

Yes never whack the center of a piston, the crown is thin and can easily be broken, cut a wood block to bear on the edges so a center hit gives an even downward force. I spent a week forcing a piston out of a 2 stroke that a mouse had lived in for years. Damned mice aren't house (cylinder) broke. Shaped wood block and threaded rods/nuts with lots of patience got it out with no further damage. I've driven out several very stuck XS pistons this way also.

 

[retiredgentleman]

That's the worst way to install pistons/cylinders. You should have waited to buy new circ clips.You were doing it somewhat blind. Haste makes waste.

The best way is to have the cylinders upside down on the bench. Lots of oil on the cylinder walls. Pistons are then lowered down allowing you to clearly see what is happening with the rings.

 

[larrynyc]

Definitely learned the hard way. Circlips are on order.

Hopefully this will save someone else from repeating my mistake. In a paid garage where there's a time limit, the urge to skip steps is always nagging. The key is to never give in. I've been pretty good about it, but it got the best of me when I discovered I forgot to get new circlips ... Well, I know better now!

Thankfully the cylinder walls weren't really damaged. There's only the slightest bit of extra scuffing on the cylinder with the bent ring, but only at the very bottom, far below the lowest point the piston will be anyway. And I saved the old set of rings, I got an old good one to replace the bent one.

Definitely a dumb mistake but I think I got out safely. The only problem now is that I lost valuable shop time (I live in NYC and have to rent shop time becuase very few of us have houses, space or garages).