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?

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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…

Clutch and Rotor Removal

When last working on the tear down of the 1981 GS650L engine I was in search of a 32mm socket to remove the clutch mounting nut. Now armed with a 32mm socket, the clutch plates removed, and my clutch basket holding tool, it was simple to remove the mounting nut.

You can then thread a couple of the 6mm bolts from the clutch springs into the primary driven gear spacer to pull that out and release the primary driven gear from the engine.

There are a few more bits and pieces behind the drive gear to remove so that the cases can be split including the oil pump drive gear and counter shaft bearing retainer.

Next it was on to the the stator side of the engine. Typical again to use a lot of Liquid Wrench and the impact driver to get the nine Philips head screws of the stator cover to free up from the engine case. Even with the screws removed, the stator cover was not budging. Ultimately, I used a large bolt through the starter gear hole to tap from the backside of the cover and break it free of the gasket.

Next was to get the rotor off of the crank shaft. It is a press fit on to the crankshaft which will allow replacing the seal behind it when the engine is rebuilt. At this point, both the clutch and the drive shaft were disconnected from the engine. If this was only a rotor issue, these would probably still be in place and you could have used the gears and jam the rear wheel to prevent the rotor from rotating while attempting to release the nut.  The official Suzuki tools for this task add up to over $200. A bit excessive for the number of times I plan to remove a 1981 GS650 rotor. I found that a 22m crows foot and and a 17mm socket were all that I needed to remove the nut, but I was glad that the engine was still in the frame since I was able to anchor one wrench on the foot peg while putting a lot of force into the other wrench.

With the M12 mounting bolt removed, it is still necessary to pull the rotor off of the tapered crankshaft. Again, Suzuki had a special tool similar to a slide hammer that would thread into a larger diameter threaded hole of the rotor to hammer it off. I found instead that you could thread in a M14x1.5 pitch bolt (< $3 at the hardware store) into this hole that would bear against the end of the crankshaft and force the rotor off of the shaft. I thought it might be better to insert something into the crankshaft to prevent damaging the surface or threads. I had a clevis pin on hand that was the right dimension to fit to the bottom of the crankshaft. It worked, but it is still a lot of force and the clevis pin deformed some before the rotor popped off.

Everything that can be removed from the engine before removing it from the frame has been done. I have continued to work on loosening all of the remaining bolts throughout the engine before removing it from the frame. The frame has been a great work-stand and third pair of hands to this point.

Small Victories

While doing all of these other activities I have still been trying to tear down the engine on the 1981 GS650L so that I can replace the broken cam chain guide. The next step was to remove the clutch cover and move further in to removing the engine internals. There are 10 Phillips head bolts holding on the clutch cover and they didn’t not want to move. Since I have time and would rather not break anything else, I have been slowly beating on it with an impact screw driver and penetrating fluid when the time was available. Finally, this weekend all of the bolts came loose. I thought the last one was going to strip before it came out, but they all came out successfully. I will be investigating options for replacement bolts before putting everything back together.

The bolts in the following picture were removed from the clutch cover in a counter-clockwise pattern from the bolt on the far right which came from the upper right of the clutch cover. The bolt four from the right was the one that ended up giving the most difficulty to remove, but none came out right away.

Once the clutch cover was off, it as time to get in to the clutch. First was the removal of the clutch pressure plate using the Tusk clutch holding tool. The pins on one side first hold the pressure plate and later the arms hold the clutch basket in place.

Springs and plate removed.

The next step is to remove the clutch mounting nut which unfortunately I did not have a socket large enough. I confirmed that it was 32 mm using an old bicycle head set wrench.

So I am off to find a 32 mm socket. I will leave the clutch plates in place until I am ready to remove the entire clutch basket.

Cylinder and Piston Removal

Continuing to tear down the engine of the 1981 Suzuki GS650L to replace the broken cam chain tensioner. Next to come off was the cylinders and pistons. All of the bolts were previously removed with the cylinder head removal, so it was just a matter of lifting the cylinders off of the studs.

Top view of the cylinders removed:

Bottom view of the cylinders removed:

And the crankcase with the pistons and connecting rods exposed and getting closer to removal of the broken rear timing chain guide:

It is amazing how much crud gets in and around the studs that tie everything together in the top end of the engine.

Next is removal of the pistons from the connecting rods. First is removing the cir-clip at the outside end of the wrist pin. I was expecting a clip with holes at the ends to grab with snap ring pliers, but it was just a heavy gauge wire. All came out easily except the No. 2 piston where the cir-clip was not exposed at the slot to grab it. Rags were placed under each piston so that the cir-clip would not be dropped lower into the engine even though the whole engine case is going to be split apart to replace the rear timing chain guide.

Pistons 3 and 4, the wrist pins slid out with just finger pressure.

And the three components of the piston, wrist pin, and cir-clip:

Pistons 1 and 2 were a little bit more difficult to push the wrist pins through with finger pressure alone, so I used a pin puller. Still didn’t need to use a wrench to pull them out, but it was much easier with something to grasp and pull them out.

With these components removed, I will now spend some time making sure that the cylinders, pistons, and rings are still within service limits, or if any further modifications need to be made.

Valve Removal and Specification Check

Continuing the investigation of the loss of compression in Cylinder No. 3 I am removing the valves and checking them against the wear limits and tolerances identified in the service manual for the 1981 GS650L.

As with most tasks, any parts removed from the engine that you plan to reinstall should go back to the same location that they came from. Therefore, it is important to keep things organized.

First was the removal of the valve shim buckets and shims. An old egg carton is handy for keeping these pieces organized for re-installation later.

Next you can use a valve spring compression tool to depress the valve retainer against the spring and remove the valve keepers. It is very easy to compress the springs with this kit that I have from Pit Posse. I have seen people use large C clamps and old sockets with the side of the socket hacked off, but that seems like more work than using this kit.

Here are the components of each valve when removed. Intake valve shown, but both are setup the same.

There was a bit of carbon built up on the backs of the intake valves, most likely from some oil dripping on to the backsides of the valves, and more build up on the exhaust valves. I soaked each pair of valves in parts cleaner for 48 hours +/- to try and remove some of the build up. The before picture is on the left and the after on the right.

Now the fun part to determine if the valves are still within specification for Valve Face Wear, Valve Stem Runout, Valve Head Radial Runout, and Valve Stem Wear. These measurements are measured in hundredths of a millimeter or thousandths of an inch. The gauges that I already have available will measure to thousandths of an inch.

The wear limit for the thickness of the valve face is 0.5mm or 0.02″. Not the easiest thing to measure, so I just set the calipers to this minimum measurement to make sure that all were greater then the minimum. No problems were found.

Next was valve stem runout which has a service limit of 0.05mm or 0.002″. This will determine if the shaft of the valve has been bent. Here is my setup to test the runout of each valve.

Handy to have the nice smooth surface of my table saw and the magnetic locking base of the clamping system. The V blocks are machinists blocks that are about 3 lbs each so that they don’t move around very easily as your are rotating the valve.

None of the valves exhibited any valve stem runout except for the No. 3 intake valve, but it was still just within the service limit.

Next was the valve head radial runout with a similar testing setup as the valve stem runout. The service limits for the valve head radial runout is 0.03mm or 0.012″.

Again, every valve was well within the service limit except for the No. 3 intake valve. Most valves were about 0.004″ of runout. The No. 3 intake valve was 0.020″ of runout. Almost double the service limit.

The last measurement was for valve stem wear. The valve stem limits are 6.960-6.975mm (0.2740-0.2476″) for the intake valves and 6.945-6.960mm (0.2734-0.2740″) for the exhaust valves. All valves were still to the upper end of the service limits. An intake valve is shown below.

All parts are kept together by their respective cylinders and intake or exhaust valves until they are ready to back into the cylinder head.

Looks like I will only need to find a replacement for the No. 3 intake valve as expected.