Topic: Jugs Stuck to Block! Stubborn...

[PGcorky]

1978 CB750f! I have reviewed as many old posts and ideas as I could find and use. The head/valves are off - so I believe every nut that holds the jugs on has been removed. But after using the rubber mallet, the torch, the wooden block and hammer, lifting, shaking, swearing, there is still no sign that this thing will be coming off any time soon. Getting a little discouraged here and even the beer didn't help this time.  One other note, she's only got 15k miles and - as best I can tell - the gaskets and such look like the factory stuff. So I don't think I'm dealing with any special previous owner stuff. Just stock gaskets. Appreciate any ideas.
Paul

[zeech]

When you turn the crank on the right side the pistons wont move at all? Could try soaking the tops with oil in hopes it will seep down and help loosen it up.

[70CB750]

Acetone and ATF 50:50 is a good penetrating mix.  Soak it and let it sit few days.

[setdog]

You have to sweet talk it a little.  Like cmon baby open up for me...

It will come off, its very common for them to be super stubborn.

Pen oil, reapply periodically, wait wait wait. 

If you choose to use a screwdriver make it a very very thin one, and be super gentle as you can't put back any metal that comes off.

[PGcorky]

When you turn the crank on the right side the pistons wont move at all? Could try soaking the tops with oil in hopes it will seep down and help loosen it up.

Pistons move sweet and easy. The head gasket had blown, and I was just replacing it - hoping to keep it simple. Unfortunately - broke off a stud while torquing things down. So now I need to get to the block!

[MoMo]

Are you using a rubber mallet or a  dead blow? Dead blow would be the better method...Larry

[zeech]

Oh well if they aren't stuck it should be a big deal. Get a screw driver underneath it like the manual says.

[scharny61]

Vinegar can help by reacting with the corrosion I hear.

[fmctm1sw]

whatever you do, be careful you don't break any fins...  ask me how I know..

[PGcorky]

Oh well if they aren't stuck it should be a big deal. Get a screw driver underneath it like the manual says.

Honestly, sometimes I love the shop manual and other times - not as much. Here's what mine says:
1. Remove the engine from the frame (see Section 5)
2. Remove the cylinder head (see Section 6)
3. Remove the o-rings, head gasket dowels, and head gasket.
4. Remove the cylinder from the crankcase.

It all sounds too easy! But in fairness, I didn't have much trouble with step 3.

[tlbranth]

I had the same problem. Nothing worked. Then a friend gave me some ironwood to play with. I made a wedge from it and hammered it into the gasket. This wedged the cylinder block from the crankcase without damaging either. I'd tried other woods but they wouldn't hold together. I think hard maple might work too but it's not as hard as ironwood. If you are absolutely stuck (and don't risk breaking fins) I'll see if I can find some of the ironwood and make you a couple of wedges.

[DustyRags]

Had the same issue with my 550- my brother finally solved it by sticking a bit of wood under the cam chain tensioner boss (you know, that bit that sticks out), and then wedging a large wrench between the two and using the wrench to leverage the jugs straight up. Not sure if that's the best method, or if the 750 even has that sort of thing sticking out of it, but it worked great for me.

The key was that it didn't try to move them sideways, the way a mallet might, but levered one side straight up.

[edwardmorris]

Just went through this with my 750 as well, its possible both the dowels are corroded into the aluminum. I used a razor blade to cut off as much of the gasket I could around the dowels, then let some oil slip in the gap, then a super thin chisel with a mallet freed it up. Rest of the gasket gave out with just pulling the jugs vertically.

[tomkimberly]

Now that you have the head off, cut some cotton rope, fill the top of the pistions and the cam areas, re-install the head (and the cam and chain), crank the engine over by hand. The pisions will loosen and lift the cylinders right off a few inches. Continue with your dis-assembly.


Tom

[PGcorky]

Just went through this with my 750 as well, its possible both the dowels are corroded into the aluminum. I used a razor blade to cut off as much of the gasket I could around the dowels, then let some oil slip in the gap, then a super thin chisel with a mallet freed it up. Rest of the gasket gave out with just pulling the jugs vertically.

I'm thinking this might be what's going on - so I'll see if I can make any progress on the gasket to get in there with some oil.

Thanks very much for all the suggestions, folks. Just need to find a little garage time now - start the soaking, and applying the heat and dead blow, and trying to remain patient.

[PGcorky]

Now that you have the head off, cut some cotton rope, fill the top of the pistions and the cam areas, re-install the head (and the cam and chain), crank the engine over by hand. The pisions will loosen and lift the cylinders right off a few inches. Continue with your dis-assembly.

I thought that had some real promise, Tom! But all I got was really nicely packed rope in the #1 and #4 cylinders.  Never did budge off the block!

[Kickstart]

Now that you have the head off, cut some cotton rope, fill the top of the pistions and the cam areas, re-install the head (and the cam and chain), crank the engine over by hand. The pisions will loosen and lift the cylinders right off a few inches. Continue with your dis-assembly.

I thought that had some real promise, Tom! But all I got was really nicely packed rope in the #1 and #4 cylinders.  Never did budge off the block!

Just reading this thread... I also thought that this was a promising idea... wondering how you attempted it?

I'm thinking you would only secure the head with the 6 bolts and leave the nuts off the studs (otherwise you're just fighting the against the studs).  I would also think you would want to do this with the cam, rockers and towers off to keep all the valves closed. 

I feel like this should work... is this what you did?  I'm kind of bummed to hear it didn't work... when I first read it I was thinking "Genius!"

[tomkimberly]

You should really stuff all four cylinders. Don't be shy, use plenty of rope.


Tom

[DustyRags]

I've heard of the rope trick being used to force valves shut, because you can stuff it through the spark plug hole. Seems to me that if you've got the head off, you can use something a bit stiff. Say, short pieces of wood. Something that'll compress less than rope. Just be sure to pad the ends so you get a reasonably wide pressure point and don't dent things (don't think you would, but depending how much pressure you create).

[PGcorky]

Now that you have the head off, cut some cotton rope, fill the top of the pistions and the cam areas, re-install the head (and the cam and chain), crank the engine over by hand. The pisions will loosen and lift the cylinders right off a few inches. Continue with your dis-assembly.

I thought that had some real promise, Tom! But all I got was really nicely packed rope in the #1 and #4 cylinders.  Never did budge off the block!

Just reading this thread... I also thought that this was a promising idea... wondering how you attempted it?

I'm thinking you would only secure the head with the 6 bolts and leave the nuts off the studs (otherwise you're just fighting the against the studs).  I would also think you would want to do this with the cam, rockers and towers off to keep all the valves closed. 

I feel like this should work... is this what you did?  I'm kind of bummed to hear it didn't work... when I first read it I was thinking "Genius!"

Hey Chris - Sorry for the slow reply on this. You're absolutely right - putting on the head and securing the studs means the jugs have nowhere to go! So I secured the head only with the two bolts that are front and back of the cam chain. So - with the lengths of rope stuffed into cylinder 1 & 4, and the head secured, I manually turned the crank. I did use quite a bit of force, but there was NO sign that the jugs were going to move.

So I'm back to soaking, dead blow hammering, and the torch. I have been able to get a thin metal scraper into the gasket space - working around the perimeter now...

[PGcorky]

I've heard of the rope trick being used to force valves shut, because you can stuff it through the spark plug hole. Seems to me that if you've got the head off, you can use something a bit stiff. Say, short pieces of wood. Something that'll compress less than rope. Just be sure to pad the ends so you get a reasonably wide pressure point and don't dent things (don't think you would, but depending how much pressure you create).

I should give this a try, Dusty. Do you think there's any danger to the valves?

[DustyRags]

I have no idea. I shouldn't think so- they're pretty tough. Maybe get a bit of rope or something similar stuffed up in there to pad it, but let something non-compressable take up the majority of the space?

Like I said, we got mine off with a lever under the bit where the cam chain tensioner attaches, but I don't know if the 750 has something like that.

[old76cr]

I had the same problem with my Norton. I finally slipped an aircraft cable through the fins between the cyl. and hoisted the whole bike up just enough to get the weight off the suspension. I used a cable hoist attached to a ceiling joist in my shed. A few taps with a sharpened putty knife and it popped off.

[PGcorky]

I had the same problem with my Norton. I finally slipped an aircraft cable through the fins between the cyl. and hoisted the whole bike up just enough to get the weight off the suspension. I used a cable hoist attached to a ceiling joist in my shed. A few taps with a sharpened putty knife and it popped off.

I honestly think that this is crucial. If I had a way to get gravity working for me, I believe I'd have an easier time of it. Unfortunately, no hoist and engine on a bench...

[MCRider]

One of my favorite tools is a teenie tiny chisel. About 1/8" shaft with a 2/16" blade. In this case you would tap (after soaking and everything else already suggested) on the 2 front outboard studs, driving into the gasket material and eventually into the aluminum, but just a skosh, and then continue all around the base gasket. Just keep tapping till you hear the hollow sound of separation. What little damage you do will be on the outside of the perimeter easily touched up.

I've done this many times, and others (edwardmorris, did he get it from me?)  here have taken my suggestion and it worked for them. But it is rather last resort. Though its always been first resort for me.

definitely if you don't have the teenie chisel don't use a larger one. You need the thinnest, but hardest blade possible to avoid damage.

Someone glued it on. Not necessary. A little heat from a heat gun might help break the glue.