disassembling seized piston

Any advice how to pull the cylinder off of a frozen piston without damaging anything? I've got it to where the entire cylinder and piston are fully extended, but they won't come apart from each other. It looks to be rusted in. It is a spare (junk) engine that I want to rebuild with a new cylinder kit. Liquid wrench? I can't really get it to soak because it drains out the exhaust port. I don't want to bend or break the crankshaft.

Thanks,

Chris

Re: disassembling seized piston

chuck russo (va) /

take the crank shaft out of the bottem end and lay the exhuast port facing up and spray Liquid wrench in it ??? i dunno if that will work , that is just the first thought that came to mind

Re: disassembling seized piston

XBrandon EdgeX /

When I had to unsieze one of my puch's, I used a ballpeen hammer and a chunk of wood. Using the chunk of wood as a makeshift chisel, Drive the piston back as far as you can (bottom dead center) and then turn the flywheel until the piston and cylinder slide out on the head bolts and are ALMOST at top dead center. then Put some wooden blocks between the cylinder and crankcase and pound the piston the rest of the way out the same way.

Re: disassembling seized piston

Good Thinking.... don`t know if any of yall have used P B.BLASTER a penetrating oil, BEST I EVER USED... Doug D

Re: disassembling seized piston

Reeperette /

I used a chunk of wood and a modified steering wheel puller....it works on Tomos, at least....gear puller or bearing puller might work too, dunno.

Worth a thought, anyhow.

-R

Re: disassembling seized piston

get the piston to as far down as it will go, then turn the fly wheel until the piston is almost as far out as it will go. Then put a couple of pieces of wood between the gasket surfaces of the cylindar and the motor. now you can use a hammer and a dull chisel type thing to turn the flywheel to pull the piston down. Its not the best thing for it but it works and what do you have to lose?

Re: disassembling seized piston

Thanks, everyone. I'll try the steering wheel puller first. If I can't make that work, I'll go for the wood blocks and the hammer. Seems to make sense. I don't have much to lose since it is a junk engine that came in on a junk bike I bought for parts. If I can rebuild it with a 60 cc kit, I'm going to do it, so it doesn't matter if I ruin the cylinder or the piston.

chris

Re: disassembling seized piston

I used four long sockets that were the same length between the cylinder and the block, and cranked away on the flywheel. It worked on an old Sachs motor, where I couldn't get to the piston. Lucky it was rust and dirt, not a full-on seize.

Re: disassembling seized piston

You're just wanting to get to the piston so you can put the new kit on, right?Don't worry about saving the jug(cylinder).Heat it up really hot and hit it with liquid wrench a few times and it'll 99% of the time come loose.You don't need that old jug and you won't have to pound on your crank.That crank will have enough stress with that new kit.What kind of engine is it,anyway?

Re: disassembling seized piston

Sorry for the late response, Don. I was out of town. It is a Piaggio engine from a junk Grande. The piston is rusted in. I don't know if it was seized prior to rusting. I'm going to put a kit on to rebuild this otherwise junk engine. Therefore, I don't need the cylinder.

Chris

Re: disassembling seized piston

So then ,Chris,heat the devil out of it and Liquid wrench it,`cause you don't even care about the piston,right?Just PROTECT the rod.That's all you care about isn't it?When you get that outside steel or aluminum REALLY hot,it expands enough to let the Liquid wrench or PB Blaster in between the piston and jug and will usually loosen up.Just don't bang on that piston too hard `cause you want to avoid damage to the rod or crank.

Re: disassembling seized piston

Thanks, Don. I'll give it a shot. BTW, where in Ohio are you located?

Re: disassembling seized piston

South central Ohio in Jackson Co.,in Jackson,OH.Where are you?

Re: disassembling seized piston

I'm actually in St. Louis, MO; but I visit the in-laws in Wooster, OH (Wayne Co.) several times a year. Perhaps some time I might be able to sneak away and see your collection?

Re: disassembling seized piston

Well,yeah,but the only real nice looking one I have is the Hero-Majestic Ankur with only 70 miles on it.The other 4 running bikes are not in pristine condition.They have dings and scuffs,you know.But I love each one of them like a faithful dog.You see,I ride a lot and washing and waxing is just not important to me.As long as that `ped gets me there and back,that's all I care.Oh,they don't look BAD,understand,just used.My BAT Starflite looks pretty good.And my black and gold Golden Bullet looks good.But I haven't run it yet.I've only got tags on my Sebrings.Been depending on my Motomarina Sebrings.What do you keep in your stable?

Re: disassembling seized piston

Mine don't really look that great either (with one exception). I bought them to ride. I have a Vespa Ciao (76), a Vespa Bravo (78), 3 Vespa Grandes (2 80s, 1 78) and a Puch Maxi (82). The Puch is pretty nice and the Vespa Bravo is in excellent condition. One of the Grandes is incomplete and in pieces. That's the one I'm trying to rebuild the motor (by the way, I got the piston free). Another Grande is not running. The third Grande runs like a champ, but looks are only fair. I just sold a 74 Ciao which was pretty nice. I'm about to sell the Puch. I think I'm going to concentrate on Vespas.

Re: disassembling seized piston

That's great you've got all those bikes,Chris! I was trying to tell some of these people on the forum that the best thing they can do is purchase an old back-up bike in case their main transport `ped breaks.I'd HATE to miss out on a ride because I only had one running bike.But some kids can't afford it.Everything on the back-up bike doesn't have to work perfectly,just safely.Well,you concentrate on Vespas,and I'll concentrate on Sebrings and Tomos bullets.Ha! BTW,how did you finally get the piston out?I'm curious.

Re: disassembling seized piston

I bought the second Vespa (a second Ciao) for the reason you describe. A kid in my neighborhood really liked it, so I sold it to him. Then, I bought a Grande in pieces and got it working again. I really liked it better. I bought the junk Grandes as a parts source, but I'm not trying to get one to run as a beater. The Bravo I couldn't pass up due to condition, so it looks like I have a collection now.

I heated the cylinder and still had to use a hammer and socket. It dented the piston crown, because it is aluminum. I planned to lose it anyway. Now, however, I'm rethinking my plan because the inside of the crankcase is corroded also. I'm a bit afraid to run it and ruin the new kit. If I can't clean it up, I have one other motor which I may rebuild with the kit instead. Thanks for the advice,

Chris

Re: disassembling seized piston

Yeah,if it's badly corroded I'd use another one.Do you mean it's corroded down around the rod and main bearings?You need that case in good shape.I wouldn't try it unless I could totally check and clean everything.Besides,you probably did a number on that rod if you dented the piston.

Re: disassembling seized piston

Believe it or not, the rod is straight. The piston is surprisingly soft. However, the crankcase is corroded in the area surrounding the rod and just behind the cylinder. I'm afraid to have any of that blow off into the cylinder. I'm going to try to clean it (with sandpaper) just for grins, but I'm not getting my hopes up. I've got another engine which has compression, so I'll probably use it and salvage the magneto, points and crankshaft off of this one for later.

Chris

Re: disassembling seized piston

Sounds like you've got a good plan,Chris! Hope it works for you!

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