CB72 stuck piston problem - again!

[gerrymoore]

Hi all. I'm in the process of rebuilding a 1965 CB72 and I have the seemingly eternal problem of the pistons stuck fast in the cylinder. I've tried WD40 for a few days and now I have a mix of ATF and Acetone in the bores..but it doesn't seem to be going down at all. I've tried the method of pushing the piston(s) using a bolt as suggested in bill silvers guide but, even with a LOT of pressure nothing is budging.

I'm not in a hurry so if I carry on with the penetrating fluid and pushing now and then with the bolt..will I win?? Is it worth trying to turn the crank?

Any suggestions welcome.

Gerry

[LOUD MOUSE]

SEE MESSAGE BELOW. .................lm

Hi all. I'm in the process of rebuilding a 1965 CB72 and I have the seemingly eternal problem of the pistons stuck fast in the cylinder. I've tried WD40 for a few days and now I have a mix of ATF and Acetone in the bores..but it doesn't seem to be going down at all. I've tried the method of pushing the piston(s) using a bolt as suggested in bill silvers guide but, even with a LOT of pressure nothing is budging.

I'm not in a hurry so if I carry on with the penetrating fluid and pushing now and then with the bolt..will I win?? Is it worth trying to turn the crank?

Any suggestions welcome.

Gerry

[LOUD MOUSE]

Bill recommended a steering wheel/pulley remover that when you have all the pressure you can turn the bolt to you hammer it then tighten again.
Years back when he mentions it was a bore to move the tool back and forth I recommended 2 tools at the same time and go back and forth.
Even with this I did have a set of pistons which I had to drill out with many small holes so they would collapse in enough to allow them to come loose. ..............lm

Hi all. I'm in the process of rebuilding a 1965 CB72 and I have the seemingly eternal problem of the pistons stuck fast in the cylinder. I've tried WD40 for a few days and now I have a mix of ATF and Acetone in the bores..but it doesn't seem to be going down at all. I've tried the method of pushing the piston(s) using a bolt as suggested in bill silvers guide but, even with a LOT of pressure nothing is budging.

I'm not in a hurry so if I carry on with the penetrating fluid and pushing now and then with the bolt..will I win?? Is it worth trying to turn the crank?

Any suggestions welcome.

Gerry

[davebern]

How about some heat cycling with a blow torch?

[Nick]

+1 Ya gotta use da heat.

car jack between upper frame rail and piston can also help

[gerrymoore]

Thanks for the replies guys ......The motor is stripped on my bench with the lower crankcase removed. I have tried WD40 from the bottom end too.

I think that heat is good advice so I will try that along with the penetrating mix and the bolt push method.

Just need patience and some luck!! Watch this space.....

[malcolmgb]

I have done this, and believe me it was well seized, I will try to find the pictures. I used Coca Cola as a freeing agent, a piece of angle iron across diagonal cylinder studs with an M10 threaded hole and bolt providing the force, I used a piece of wood between the bolt and the top of the piston, it took 3 weeks of constant pressure occasionally changing from one cylinder to the opposite. No heat was used simply because I believed the only thing that would release was the liner. It's also important to note that if the pistons are at either TDC or BDC you will have major problems because you are the just pushing against the con-rod and the crank will not turn enough.