cylinder removal 1981 CB 750

[PeterRedford]

I have hit a bit of a stuck point.

I'm tearing into my 1981 cb 750. I can't get the cylinders off of the crank case.

I have tried everything next to prying it apart.

my manual also says to remove a bolt at the front which mine has a nut not a bolt on it and isn't really long enough to get a second nut onto to thread off.

wondering if anyone else has had this much trouble removing it.

 

[amc49]

Many do when water gets down in stud holes to rust the studs to the block. People break the cylinder block from it too if not careful.

 

[Chris in Dorset England]

Many do when water gets down in stud holes to rust the studs to the block. People break the cylinder block from it too if not careful.

Hello,
I have a similar problem, I have removed the stud and small nut, however the cylinder block is totally solid and resists all my attempts to remove it. As I don't want to damage the block is there a way of getting it off? I had considered heat but am wary of over heating and melting or warping the block. Any advice would be welcome.

Thanks.

 

[amc49]

You gotta be inventive and solid thinking there. And a few will tear up regardless of how careful you are anyway. I myself do not use heat, it really does little. Best thing to start is like Liquid Wrench or PB Blaster or WD40 well soaked into the stud holes and let it set a week before the effort. It's almost always the studs and stud holes that are the issue. The stud holes break out of the casting at the fins and then rain runs in to corrode at the base of studs where they enter the lower cases. You can aid things somewhat by double-nutting and yanking the studs that come out easy and it also shows the problem ones. Less studs in place and the block can move around more to come off. If an F engine the studs are spiral knurled and as stout as any aftermarket specialty ones but if the plain shank studs they twist in two at the drop of a hat FYI.

 

[Chris in Dorset England]

Hi,
thanks for the advice, I have done what you advise with much WD 40 and a mix of kero and oil and will leave it to soak. I found a web site where a chap came up with a device to pull the block up using the studs and a home made nut between the fins, it seems to work. It's the 4 centre studs I can.t get out, totally solid.
I will let you know how it goes.

Chris.

 

[Chris in Dorset England]

Hi, well after a 3 day fight with the four centre studs I got the 2 rear ones out, the front 2 were having none of it . Desperate times called for desperate measures I have a very thin, old and blunt kitchen knife, so I decided to go for it picking a place as close as possible between the 2 studs I tapped the knife into the joint between the crankcase and cylinder block, to my surprise it went in reasonably easily. I wriggled the knife about from side to side making a narrow gap. Next doing the same with a small, thin screwdriver, the block seemed to move up just a few thou! Next a slightly larger screwdriver, the block DID move up, I had a gap now of about 25 thou. That was enough to get plenty of WD40 into the gap and onto the stud and block. I left it to soak overnight and then another soaking with WD40. Grabbing the block in both hands and attempting to twist the whole thing to and fro seem to loosen the grip of the corrosion , more WD40, more twisting,pulling and slowly and reluctantly the cylinder block moved up the studs off the end of the machined section and was free at last I don't drink but some strong coffee did as well.

 

[amc49]

Look CLOSE at your stud threads, often the center studs come loose taking part of the case thread with them. Then the case/stud holding power drops way off.

 

[Chris in Dorset England]

Look CLOSE at your stud threads, often the center studs come loose taking part of the case thread with them. Then the case/stud holding power drops way off.

Hi, Thanks for the advice, everything looks fine. I have given up on the 2 that remain, it's inconvenient having them there but better than breaking things, cheaper too! by the way, I always read your answers to others here, I have learned quite a few tips from your answers, thanks.