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Removing severely stuck pistons
- Thread starter Myowncreation
- Start date
Soak liberally with your favorite penetrating liquid, I like PB Blaster. Let it soak for a good long time Like over night. If you have an electric heat gun, no torch, you can try heating the cylinders, This may help the fluid penetrate as well as the expansion of the cylinders may help break the grip of ther rust.
Lift the cylinder up as far as you can. Slip wood shims between the cylinder and block. Used a wood block and a BFH to drive the piston down. A few whacks on one piston, then a few on the other. You can't drive just one at a time. If you can't get them to move soak them with more lube, let set at least over night for the penetrating fluid to work.
As you drive the pistons down lift the cylinders and add more shims. Eventually the cylinders will come up off the pistons.
It can take a long time to get it apart.
If it's that bad, there is a good chance the crank and transmission bearings are rusty too. The crank bearings can be hard to find and cost a lot. When I rebuilt my 75 crank it cost me about $450 in bearings and rods.
Leo
Lift the cylinder up as far as you can. Slip wood shims between the cylinder and block. Used a wood block and a BFH to drive the piston down. A few whacks on one piston, then a few on the other. You can't drive just one at a time. If you can't get them to move soak them with more lube, let set at least over night for the penetrating fluid to work.
As you drive the pistons down lift the cylinders and add more shims. Eventually the cylinders will come up off the pistons.
It can take a long time to get it apart.
If it's that bad, there is a good chance the crank and transmission bearings are rusty too. The crank bearings can be hard to find and cost a lot. When I rebuilt my 75 crank it cost me about $450 in bearings and rods.
Leo
I had good results with Marvel Mystery Oil into the spark plug holes, engine still together and in situ. After a few days of setting I gave the crank bolt some good whacks using a breaker bar and a rubber mallet. About the third whack she freed up. An air impact wrench would have done it also.
tonyc
XS650 Guru
I had to pound my pistons out with aluminum round stock and a big hammer, It will need a rebore any way. This would be the last resort as was mine.
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The rusted up engine I had, once apart needed a rebore. The crank bearings were rusty too. You could feel them as well as hear them roll across the rust spots.
If your crank is good then you can rebore as needed to clean up the bores and use oversize pistons.
You can also go with a 750 kit from Mike's. He also sells a 650 version of the big fin cylinders with stock bore. As well as stock sleeves you can put in your cylinders for a stock piston.
Once apart and inspecting the crank and rods, the options are many.
Leo
If your crank is good then you can rebore as needed to clean up the bores and use oversize pistons.
You can also go with a 750 kit from Mike's. He also sells a 650 version of the big fin cylinders with stock bore. As well as stock sleeves you can put in your cylinders for a stock piston.
Once apart and inspecting the crank and rods, the options are many.
Leo
FLEA
XS650 Guru
if you have the time,take the head off, hang the engine in the air a few inchs and fill the top of the cyclinders with oil and let gravity do the rest then after a week or so if the pistons havent moved resort to the other ways at least you might have loose them up
Tomterrific
XS650 Junkie
Head off, oil. If the pistons are at the top of the bore, you can start. If the pistons are at the bottom, do as Leo says and lift the cylinder. Use a wood 2x2 on the piston tops. Bang one, then the other. If one is moving and the other is stuck, you should be able to see the problem since they are connected through rods and crank. You will probably find the rust at the top. If you are lucky there will be only a light amount. It doesn't take much to stick the pistons.
Tom
I've been thinking I'd get a large tank and fill it with old motor oil and kerosene. Put a winch above it and the next old bike I buy, I'll drop it in the tank of oil for a few days before I start working on it.
Tom
I've been thinking I'd get a large tank and fill it with old motor oil and kerosene. Put a winch above it and the next old bike I buy, I'll drop it in the tank of oil for a few days before I start working on it.
FLEA
XS650 Guru
Tomterrific
XS650 Junkie
Hi Flea,
Yeah, it's a joke but won't it be great if you could actually soak an entire rusty motorcycle in oil! When my friend called and told me he bought an XS650 for $100, he was excited. 24 hours later he asked me to trade for something because it was a rusty POS. My first look nearly had me run also but said friend did something cool. Knowing the bike would need some disassembly, he sprayed the entire bike with penetrating oil. It seemed to work.
Tom
Yeah, it's a joke but won't it be great if you could actually soak an entire rusty motorcycle in oil! When my friend called and told me he bought an XS650 for $100, he was excited. 24 hours later he asked me to trade for something because it was a rusty POS. My first look nearly had me run also but said friend did something cool. Knowing the bike would need some disassembly, he sprayed the entire bike with penetrating oil. It seemed to work.
Tom
