Finishing the Lower End

The engine rebuild for the 1981 Suzuki GS650L is starting to come together and the parts bin is starting to empty out. It is great to be able to get the original shop manual for a bike that is over 30 years old, but the photos taken during the tear down are invaluable. The old grainy, B&W photos of the 1981 service manual that were then probably and scanned to PDF are a little tough on the eyes.

Once the crankcases are back together, there are only a few big parts to reinstall before the lower end is pretty much complete. On the left side of the engine it is just the starter idle gear and rotor.

Before reinstalling the rotor, I did replace the 3 roller and spring assemblies of the starter clutch. Fairly cheap money to replace these components as the springs are barely more than you would find in a ball point pen. One of the original three springs was fully compressed in its slot, so it was probably a good time to take care of this upgrade.

The starter, gear position indicator, and stator will wait until the engine is back on the bike since most of these pieces are still connected to the wiring harness within the frame of the motorcycle.

The right side of the engine has a few more pieces that really start to bring the engine together. The oil pump and its gears, the gearshift shaft, the drive gear, and signal generator are all installed from the right side.

Gearshift shaft:

Oil pump and pump drive gears:

The primary drive gear, clutch sleeve hub, clutch plates, and pressure plate:

And finally the signal generator on the crankshaft:

Similar to the left side, the signal generator and clutch cover will go on once the engine is back in the frame.

The lower end of the engine is now operational. The crankshaft is connected to the drive gear and the transmission.

The parts bin is looking a lot better at this stage too:

More to do once the top end starts to come together, but I am thinking I will want to reinstall the engine to the frame before proceeding further. It is getting pretty heavy at this point.

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Oil Pan…

As you would expect on a 37 year old motorcycle the outside and inside of the engine oil pan were quite a mess.

Here are a couple of pictures from when the oil pan was removed from the engine.

I soaked the oil pan for a while in the Berryman’s parts cleaner. It did a pretty good job of getting the old gasket and grime off of the oil pan. With a little more cleaning it was ready to go for painting.

One additional thing I took care of before reinstalling the oil pan was to remove and clean the oil sump filter. This was probably about 50% clogged with just as much sludge as was seen in the oil pan.

With the oil sump filter reinstalled and a new gasket the oil pan was ready to be installed to the crankcase.

Now I can flip the engine back over and get started on the top half of the engine.

Getting Started on the Rebuild

Last year the rear came chain guide inside the engine of the 1981 Suzuki GS650L snapped in half causing the timing to jump and bend one intake valve. Since then I had been tearing down the engine to remove and replace the broken cam chain guide. It is fitting that as I start to rebuild the engine, the first piece to go back in is the new cam chain guide that I was able to obtain from eBay.

The next steps are just dropping the crankshaft back in, the main shaft, the output shaft, and the secondary driven gear assembly to the upper half of the crankcase.

The only pieces that are installed in the lower crankcase half before joining the two halves together are the gear shifting cam and the gear sifting forks. With the transmission set in neutral and the gear shifting cam in neutral the two halves of the crankcase can be joined together.

There are quite a few bolts and different sizes holding the crankcase together, so I did a dry fit first to remember where they all go…

Once that was figured out it is necessary to apply a liquid gasket to the mating surfaces of the crankcase. Since the manual is 27 years old and things change over the years, there is not a lot of agreement on which bonding product is best. I went with Honda Bond which had similar characteristics as the original Suzuki Bond No. 1215.

The only trouble I had with the Honda Bond was that as I was trying to squeeze it out of the nozzle it blew out the end seal of the tube. Got a little messy, but it still worked out ok. Just won’t have that tube for another use.

Once the two halves were lined up and the bolts torqued to specification, the crankcase was looking pretty good.

Next, I need to finish cleaning and painting the oil pan so that I can get that installed and flip the engine back over to continue on the top end.

Cleaning and Painting

One thing that I thought I was going to have plenty of time to do this winter was to clean and paint the engine cases before putting the engine back together in the spring. Turns out it is cold in the winter and not that easy to clean some of these components. For some of the smaller pieces I was able to soak then in my parts cleaning 5 gallon bucket which striped off the old paint and other dirt to get them ready for painting. The engine cases were too large for the 5 gallon bucket which required some warmer weather and outside, running water to get things done.

The cylinders and cylinder head fit in the 5 gallon bucket which was nice due to all of the nooks and crannies.

I didn’t take many photos of the cylinder head before cleaning and painting, but the following is close.

After it was dipped and cleaned as good as I could, I had to mask off all of the areas that I did not want to get painted.

For all of the circles that cover the various threaded wholes, I used a socket to cut circles out of the masking tape.

I then used primer and paint from VHT (Very High Temperature) paint. Cast aluminum was the color choice for the final paint color.

The cylinders went through a similar progression.

Before:

Masked:

And painted:

The two halves of the engine case were more of a challenge as they couldn’t fit into the parts cleaning solution. I tried a number of things from Gunk Engine Degreaser, brushing on parts cleaner, wire brushes by hand and in the drill, but in the end the one that worked best was POR-15 Cleaner and Degreaser.

Bottom half of the engine case before:

Cleaned:

Masked:

And painted:

The same was done for the top half of the engine case, although a bit more masking effort since I did not pull the cylinder studs.

Top of engine case before:

Cleaned:

Masked:

And painted:

It was probably a good thing that the engine cases did not fit in the parts cleaner since no damage was done to the internal paint in some areas, but it would have been helpful for removal of the old bits of gasket still stuck in various places. Lesson learned was that I should have done a better job of old gasket removal before painting. The gasket removal work that still needs to be done could potentially do some damage to the new paint that will need to be touched up.

There are a few more pieces to clean and paint, but at least now I can start rebuilding the engine.

Splitting the Cases

The point of all of the effort to date on the 1981 Suzuki GS650 was to be able to split the cases to remove and replace the broken rear cam chain guide that is pinned between the two halves of the crankcase. With the oil pan removed it is now time to remove all of the remaining bolts that are holding the two crankcase halves together.

Again, the manual indicates that a mallet might be able to separate the two halves of the crankcase. This must only work when the engine is brand new since there are four alignment pins between the cases and there is no way you are going to tap the side of the crankcase and get it to release vertically. To solve this issue, I purchased the official Suzuki tool to split the crankcases. $60 well spent.

Then it is just a matter of lifting the lower case off of the upper case.

The slot that the rear cam chain guide is fit into can be seen here:

And removed along with upper half that was previously loose within the cam chain cavity.

So other than putting everything back together to have a running motorcycle engine again, removal of the broken rear cam chain guide has been achieved. The question now is how much more work do I want to do now to clean up the engine before it all goes back together?

Oil Pan Removal

The next item to remove from the engine of the 1981 Suzuki GS650 is the oil pan so that a few internal bolts can be removed that will continue to hold the two halves of the engine crankcase together.

There were 17 bolts to be removed from the oil pan.

Once all of the bolts are removed, the manual suggests that tapping the oil pan with a mallet will release it from the crankcase as there are no alignment pins and only the gasket holding it in place.

Like the stator cover, the oil pan was not budging and there is no access to try and knock it off from the inside. A thin metal putty knife was able to be worked in to the gasket edge to release the oil pan from the crankcase.

A nice amount of sludge in the bottom of the oil pan.

And there were also quite a few more bits of the broken cam chain guide than I expected to find. At least they don’t appear to have circulated any further although some were in the oil pump screen.

 

Engine Removal

I have finally gotten to the point where I can remove the 1981 Suzuki GS650 engine from the frame. There are a number of smaller brackets attaching the engine to the frame and three major bolts that span through the engine block from one side of the frame to the other. Like everything else, I have been frequently applying Liquid Wrench to each bolt as I am working on the other components. It still took a combination of Liquid Wrench and a blow torch to heat and cool the nuts to get everything released successfully. For the three larger bolts, I continued to use the left foot peg as a third pair of hands to hold one wrench in place while I worked from the right side of the bike.

With all of the bolts released, the engine still sits deeply in the lower frame and is awkward to try and lift out of the frame. I used the jack from the truck to raise the engine above the frame and placed runners across the frame to more easily slide the engine out.

And it’s out.

Plenty more bolts to remove to be able to split the engine, but the majority were loosened while the engine was still in the frame…