Suzuki GT750 Cylinder block removal

Getting the cylinder block to come off or move at all seems to be a serious problem on engines that have not been apart for a long time or ever before. People around the world have stalled GT750 engine restoration projects laying around on shelves where they failed to get the block off. Residues build up between the stud bolts and the holes that go through the cylinder block and can make it difficult to have the block move.
Years of chemical reactions from leaking cooling fluid and water entering in from above can cause the studs to bind real hard to the block. Two main methods exist for pulling the block. One is to manufacture a puller plate bolted onto the cylinder block (using M8 bolts), with threaded holes that allow screwing down bolts into the cylinder block holes so they push against the cylinder studs. This will have the block be pulled upwards. It is a good idea to soak the stud holes with penetrating fluid (WD40, etc) some week(s) before so any serious corrosion is softened up.

The other method is to thread the stud holes using a 5/8" tap. The holes are appr 15mm diam at the uppermost section cavity where the head bolts normally go. By threading this hole and screwing down 5/8" bolts in an even fashion the cylinder block will be pulled upwards. I haven't tried this myself but I got myself a 5/8" tap at a parts market that will be handy if I should need to try this in the future :

5/8" tap, unusual extended model. This particular length is no advantage for the use discussed here but it serves as an illustration of a 5/8" tap...

In my case I used the actual cylinder head as a puller plate. That is not recommended because there is a risk of
warping the head if applying excessive pulling force. Anyway I succeeded by using this method so likely my block wasn't seriously stuck.

In order to get the stuck cylinder block off I manufactured a puller tool that used the cyl head as a puller plate.
When the bolts are turned the washers with welded-on nuts press upwards against the head which is bolted to the cyl barrel
using the smaller M8 bolts. This works to pull the cyl barrel upwards. Bolts must be turned evenly to yield an uniform force and to avoid warping the head. Take care ! I don't recommend using the actual head the way I did here, rather use a massive plate if you have the patience to have one made for you.

Shows the M8 bolts that hold the head to the block.

Dual M12 nuts locked against
each other on threaded rods
creates a set of pushing bolts.

Nine washers press against head bottom surface, a M12 nut is welded onto each washer. Turning the threaded rods will pull the cylinder block.

This is how far the M12 pusher bolts could pull the cylinder. It still won't come off, a few studs still prevent removal by hand. I will try making a M10 bolt set tomorrow which can press all the way down the stud holes. Then the cyl will likely come off.

2nd attempt - M10 puller setup

I manufactured a new set of puller bolts and washers using M10 threaded rods. This allows pushing all the way
down the stud holes. This worked very well and I didn't need to turn bolts
hard enough to risk damaging the head. By turning all bolts evenly the block moved
upwards. A very successful method in my case.


Ready to begin the pulling

When I got the block to this level it began loosening up and after a while I could lift it off by hand !

This picture shows the two sets of puller bolts. The long threaded rods and nuts need of course not be metric, in case you can easier find similar threaded rods in your country this will work equally well. The M12 ones are useful for the first stage when getting the block to move. They can be used to push as far down as the upper diam of the stud hole reaches. When the studs has been pressed down that far then the M10 size bolts serve the purpose of being able to press all the way down the stud hole. Eventually you would only need the set of M10 size ones, but the M12 ones fit better while pushing down in the upper part of the stud holes (that are wider). The smaller bolts shown are in M8 dimension (75mm and 55mm length) (these need to be Metric so they fit the M8 threads of the block!) and is used to hold the head against the cyl block. When used with the M10 bolts/washers the head sits closer to the block and I used M8 nuts as washers on the 75mm bolts to compensate for their length. When used with the M12 bolts the puller washers/nuts are thicker, then the 75mm M8 bolts require thin washers instead of the M8 nuts shown in the picture..
Both the M12 and M10 bolts are made up of 1 metre threaded rods divided into equal lengths and nuts locked against each other to create a bolt head on each of them. The large washers on the pulling studs were welded to nuts to create threaded washers that push against the cyl. head.

Suzuki GT750 Cylinder stud hole boring bar

This was my first attempt in trying to get the cyl block off. I had this tool manufactured to clean out the stud holes in the cylinder block. An ambitious and costly project. But, I learnt the hole diameter changes further down in the block and it is not possible to bore all the way down the studs. So this tool only serves to clean up a depth slightly further than as far as the head bolts go.

This tool IS useful for cleaning up and CAN help in getting rust penetrating oil to
reach down around the studs. But it is not directly effective for getting the cylinder barrel off.

* * SUMMER SALE * * I will now sell four of these special order 'tube drills' for $30 a piece + shipping. US $40 total to the U.S. or Australia.
It costed me about $200 total to have five manufactured :-(
You would have to file the teeth yourself according to the below pictures, quite easy.

Cutting teeth finished !

This is how far down the bar will go,
then the hole diameter changes.

Revised parts for reinstallation - HEAD NUT WASHERS

There exists a later type of washer for the head bolts that will seal against water entering into the
cavity where the head studs and nut go. This helps reducing the tendency for corrosion and thus less difficulty getting the cylinder barrel off the next time you or somebody else have to do this job again.

I got these sealing washers from Paul Miller.

This is how they seal when installed.

This shows a head bolt that came with a used cylinder block I bought. It had been sealed using this type of washer and you can see the chrome remains perfectly intact.

Here is another bolt that spent its life without a sealing washer, see the difference !

The collected Wisdom of the World

For your convenience click here for traffic that occurred on the GT750 mailing list some time ago regarding cylinder removal.
If anybody find their posting there and do not want it to appear on that page please contact me so I can remove it.

Here is a page that shows the same priunciple using a dedicated barrel plate instead of a more delicate alloy head :
(C)2001 Gunnar Forsgren, All rights reserved