Reassembly Woes: Stuck pistons

[Guest]

You probably scratched your cylinder walls. A new cylinder may be in order or oversize pistons.
Sorry to say.

[67fire]

Chef wrote: "You probably scratched your cylinder walls"
I think that you are trying to be kind, I was thinking more like gouged.
Over-bore or cylinders, imminent.

Eric

[GregT]

Most motor reconditioners/machine shops are used to doing car motors so ignore the lead in tapers at the bottom of the bores.
I find it pays to clean up this taper with a fine half round file and remove the acute edge left by the boring job.
Ten minutes spent here can save a lot of grief later

Greg T

[Matchless]

Very unfortunate, but I know someone who did it 4 times in a row! He bent a few oil ring scrapers every time. The only way those pistons are going to come out is by carfully tappng them with a piece of wood and a hammer and with some wood under the cylinders.
The chances are good that you have damaged the pistons, rings and the cylinders. Inspect them carefully.
My sympathies!

[ameen]

oh damn.....thats what i was worried about.. This has turned in to a two month rebuild process. Well when and if i can get it out, i am not sure i want to sink any more money into it. Ebay may be seeing a lot of gs550 parts real soon.

I will get some pictures tonight. FML.

[flyingace]

For the future, there's a thread here on using some wooden blocks for holding up the barrels and large ring clamps as piston ring compressors. It worked like a charm for me my first time.

As to the current situation, most everyone who does mechanical work has been in this kind of situation. Seems to me you need to decide that a cylinder bore and new piston/rings will be required, and use whatever force is necessary to get the stuck piston out.

[67fire]

Think positively. You may have only damaged a section were the piston and rings does not ride.
Then, you will only need to hone and clean up the damaged area. Also, as mentioned earlier, the lower part of the cylinders is tapered to ease the install process.
Taper the taper a little bit more where it meets the cylinder bore and when you go to re-install, smear plenty of white assembly grease in the taper and on the rings and piston skirts.
You may only have to do minimum work and only need a couple of sets of rings in parts. Still cheap!

Eric

[Dogma]

On my 850, The pistons sometimes tipped on the way in, jamming them. In that state, they didn't want to come out either. If this is the case, you'll be able to see one side of the piston skirt looks to be sticking out less. A little tapping with the handle of a screwdriver freed mine so I could try again. But then, I never whacked the cylinders with more than the palm of my hand. I hope that's all you used.

(New to this thread and just skimmed it. Sorry if I missed a relevant detail somewhere.)

[ameen]

unfortunately i pushed a little harder than that...

here are some pics

[ameen]

another pic..

[ameen]

and another...

[ameen]

and one of the bike... i can post more ifanyone wants

Thanks

[gearhead13]

Jeez that sucks, man.
Have you tried blocking the cylinder up with a 2x4 or something and turning the crankshaft?

[reddirtrider]

Yea, I'd wrap shop cloth around the bottoms of the pistons then block the cylinders up and hit the tops of those pistons with another piece of wood driven by a hammer.

The reason for the shop cloth is to keep the pistons from hitting anything after they come loose and causing additional damage.

The cylinders are pretty sturdy and I doubt you've damaged them so far. Light scratches can be honed out. Check everything over when it's disassembled and perform a ring end gap measurement to make sure they are the right size.

Get another pair of hands when putting it all together next time. Don't force anything. If it feels like it's binding start over.

[Guest]

Number 2 is in cockeyed. Try tapping the bottom of the skirt and see if you can straighten it out. Try using a small ball peen hammer if you have one.