Topic: Engine cylinders won’t come off?

[Translations]

I am in the process of rebuilding my 78 cb750f2 and I’m having a hell of a time getting the cylinders off the engine. The strange part is the pistons are not seized and I actually got them up about 3/4 a inch off the base but they refuse to lift any further off the engine. Had anybody run into something like this before or have any ticks or advise?

[Bodi]

Well, I see the cam chain. And I don't see a wire holding it from dropping down the tunnel. It is off the cam, right?

[Translations]

Well, I see the cam chain. And I don't see a wire holding it from dropping down the tunnel. It is off the cam, right?

The head came off surprisingly without issues it’s the cylinders I can’t get off but the chain is being held by something so it doesn’t fall through into the case.

[Alan F.]

I think if you can raise it 1/2" that all of the Dowell pins are exposed so it's not them holding it. It's either piston rings rusted stuck to the cylinder walls, but if you spray a little oil in there can you rotate the crank?

That only leaves the fit between the OD of the cylinder sleeves into the upper case half, what happens if you add heat?

[Jerry Rxman Griffin aka MuthaF'er]

Raise up the cam chain so it's on the crank sprocket, hold it up with a screw driver etc and rotate the crank to get it to move the pistons??

[Translations]

I think if you can raise it 1/2" that all of the Dowell pins are exposed so it's not them holding it. It's either piston rings rusted stuck to the cylinder walls, but if you spray a little oil in there can you rotate the crank?

That only leaves the fit between the OD of the cylinder sleeves into the upper case half, what happens if you add heat?

I’ll let it soak in penetrating oil tonight and see how it goes tomorrow thanks for the advise!

[bryanj]

The exposed studs get crap in the holes at the bottom and top so the studs go through where the plain bit is but stick on the threads, only way i found is to keep working barrells up and down till stud threads clean out holes.

[Alan F.]

The exposed studs get crap in the holes at the bottom and top so the studs go through where the plain bit is but stick on the threads, only way i found is to keep working barrells up and down till stud threads clean out holes.

I was wondering about that but have never seen it myself.

Perhaps if you're familiar with removing these cylinder studs (and of course if you planned to anyway)
now would be a good time to take out the easy ones, thinning the herd so to speak?

[madmtnmotors]

Did the motor spin freely prior to disassembly? If not, one set of piston rings could be seized which would permit lifting the cylinders until that particular piston reached TDC.

[bryanj]

Happens a lot on the 500/550 which most studs exposed, most 750 are enclosed only the ones with domed head nuts and copperised washers (F2-3,  not sure about K7-8) have exposed studs

[Alan F.]

I think K7/8 studs are enclosed. This summer only 3 studs on my K8 were too stuck for the double-nut method, had to grab it with 2 pair of vise-grips down low and they broke loose first try.

[Translations]

So it ended up being one of the head studs that was completely rusted to the cylinder so I ended up having to take a a cutting wheel to it to get it off. Im pretty sure this motor has never been taken apart and its fighting me the whole way I am used to working on newer bikes this old girl is throwing me for a loop!

[Alan F.]

You may want to replace those stock studs with A.P.E. heavy duty studs.

[Translations]

You may want to replace those stock studs with A.P.E. heavy duty studs.

I agree Alan that will defiantly be on the top of the rebuilt parts list.

[madmtnmotors]

this old girl is throwing me for a loop!

Working on the older bikes had made me quite adept at removal of broken fasteners!