Same engine '82 GS650EZ and GS650GL?

[Guest]

I just picked up an inexpensive, non-running, partially completed cafe racer build on a 1982 GS650GL. Not running at purchase. Came across an inexpensive '82 GS650EX motor and trans running. I know the GL is shaft driven and the EX is chain. Question is, can I poach the engine from the EX for the GL? Don't want to complete the build only to find the original motor is junk.

[Steve]

There are a few parts that will cross over, but forget about switching engines.

As you have noted, the GL is a shafty, the E has a chain. The frames are different to accommodate the different drive systems, as well as the swingarms.

The cylinders and heads will interchange, but the cams need to remain with their original crankshaft. The sprockets have different number of teeth, so they don't stay in sync. It might be possible to simple change the cam sprocket, but I had no way to verify the cam timing when I did this, so I simply used the other cams.

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[Big T]

Non running is typically not an issue with GS motors, save the Gen 2 750.

Adjust the GS valves, then do a compression test. If they're relatively even, it should be able to be revived

The G and E cranks are totally different

[Steve]

There are a few parts that will cross over, but forget about switching engines.

The cylinders and heads will interchange, but the cams need to remain with their original crankshaft. The sprockets have different number of teeth, so they don't stay in sync.

The G and E cranks are totally different

As we both have hinted, there <are> a few pieces that will cross over, but the engines are totally different.
The E has one-piece rods, roller bearings, a pressed-together crank and a low-pressure oiling system.
The G (and GL) has two-piece rods, plain bearings, a solid crank and a high-pressure oiling system.

Some time during the '82 production run, there was an extra bolt added to hold the valve cover to the head. Of course, the head and the cover were both affected, they do not interchange. You can install an '83 head and cover on an '81 bike, but you have to move the head AND the cover.

Valves, springs, buckets and shims are the same. Cam chain tensioner is the same. Stator is the same. Ignition is different on the '83, the advance is electronic and is built into the ignitor, not using the mechanical advance on the end of the crank.

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[duaneage]

Ignition is different on the '83, the advance is electronic and is built into the ignitor, not using the mechanical advance on the end of the crank.

The 83 engine is identical as far as far as ignition advance. I swapped an 81 for an 83 without issues.

[KillerGriller]

The cylinders and heads will interchange, but the cams need to remain with their original crankshaft. The sprockets have different number of teeth, so they don't stay in sync. It might be possible to simple change the cam sprocket, but I had no way to verify the cam timing when I did this, so I simply used the other cams.

I have to replace the head on my '82 650E, bought a used head that came from a 650G that I was told "would work", the cams look the same but the cam sprockets are very different:

Camshafts - The cam shafts from the E are the same size and orientation to the G, but the E shafts are stamped with "R6" and the G "R4" (opposite side of the shaft and sprocket to the EX or IN stamps)

Camshaft Sprockets - The sprockets from the E are smaller and are stamped with 470, the ones from the G are larger and stamped 342.

I tried installing the cams from the G which didn't work, but I can't seem to find a pic that shows the proper size for a 650E sprocket? Comparing photos from Ebay the 342 sprockets look like they are the proper 650G size, and I did find a pic of an '81 550 sprocket was stamped 470, did the 650E use 470 sprockets instead of the 342 used on the 650G?


As an FYI from my searching:

'81 550 - 470 Sprocket
'83 550 - 434 Sprocket
? 750 - 454 Sprocket
? 1100 - 490 Sprocket