Cylinder head

[K2-K6]

If they are really not going to move and they are stopped away from TDC,  then you can use a piece of softwood near the bore size and thump each piston in turn using a lump hammer.

This'll usually break the corrosion bond and allow you to rotate the motor.

It's more sympathetic than going through the crank and rods with a really big lever.

[Bryanj]

Bill use a 50/50 mix of acetone and tqf, the yanks swear by it and i saw it work on the repair shop on tv, also trying it on an old engine and it seems to be working

[paulbaker1954]

My engine when I rebuilt it was so hard seized nothing would shift it

Eventually If I remember rightly I removed the oil pan and then managed to get big end bolts off which allowed me to lift the barrels off with the con rods and pistons.

Then I was just dealing with trying to hammer out individual pistons.

Even then I couldn’t shift them and ended up getting the pistons pressed out in a local machine shop.

The good news was that despite how badly seized it was the bores just needed honing and were still within original spec

[Tomb]

I had an old unit 500 Triumph engine with seized in pistons, nothing would shift them until I tried cheap nasty cola (coke) this stuff ate through the corrosion and the pistons came out easily.

[royhall]

Interesting topic! In my archives I have several socalled Rider's Reports on the CB500/550 published back then in then a weekly (!) motormagazine. In these articles were the typical complaints listed that CB500/550 owners met during many years and kilometers. High on the list were the plugcaps. Also high was the almost inevitable sweating of oil at the head gasket. In one of these articles the chief mechanic of Honda Netherlands, the man at the importer that instructs the dealers, gave his advice. Before tightening the head nuts, he advised to oil the washers somewhat with Molykote and then torque down to the original torque values prescribed in the Shop Manual. Can anyone explain how this can be benificial? I always thought torquening bolts/nuts using grease is a no-no. Now here the advice concerns the washers, but still I would like to know.

Torque figures are usually given for dry threads UNLESS it's stated to use a specific lubricant.

Torque wrench effectively measures friction (rotary in this case) so placing a lubricant on the washer and using the same torque setting figure will then stretch the stud more than without lubrication.  A higher clamping pressure in applied,  as long as the tensile strength of the stud is not breached.

It's a more involved topic for such a simple action than is generally realised, we could do a thread on that if wanted.

Interesting point there. If it's just a quick repair and the threads are not degreased they will have oil on them and so will the nuts. I doubt anybody goes to the trouble of degreasing the casing studs for a head repair, or am I wrong? Therefore by default you will be torquing down lubricated threads so what's the calculation to get the torque required from dry to oiled threads?

[K2-K6]

Definitely Roy, you were paying attention at back of class there 

The numbers I've got say 10 to 15 % for a change from rolled threads dry to using oil.  They differ for everything that can affect them including thread manufacture,  plating or not, bolt / stud material,  nut / washer material and design.

As you point out,  it's just as important to have them all even for the structure you are securing to get correct distribution of clamping.

Whatever method anyone uses, the Honda figures seem to be given dry so you'd have to start from there and make decisions based on that.

We did talk (torque  )  about it in relation to the small fasteners on another thread with Laverda120,  but I can't find that one just now.