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I can't say that I know most of the tips and tricks of the swap, but I did find an interesting tidbit last night for those who are considering this upgrade.
I am working on a 650GL for another member. The engine has three intake valves with a LOT of excess clearance. (The story behind that is best left to be told by him.
) On my suggestion, he purchased a spare 650E engine from member "witttom", hoping that we would be able to scavenge some parts for the GL.
In the course of acquiring all the excess valve clearance, a couple lobes on the intake cam were chipped on the edges. Because of that, we decided to use the cams from the E, which were perfectly pristine. The parts fiche confirms that ALL GS650s (including the X85 Turbo) use the same cams. After the requisite replacement of the base gasket, we installed the cylinders and head. After installing the E cams, I did the usual "turn the crank at least two full turns by hand". Or, at least I tried to go two full turns. I got to about 1 3/4 turns and the crank stopped NOW, with a noticeable "clunk".
We backed up, re-timed the cams and tried again. And AGAIN. For some reason, Exhaust valve #1 was being held full-open as piston #1 was coming up. 
Visually, the timing marks on the cam sprockets appeared to be the same, then we found the difference.
The 650E cams have 30-tooth sprockets. The 650G sprockets have 34-tooth sprockets.
Evidently the crank sprockets have 15 and 17 teeth, respectively.
I don't know how many teeth are on the 550 sprockets, but thought I would pass on this little tidbit for those that might be chasing some parts.
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I am working on a 650GL for another member. The engine has three intake valves with a LOT of excess clearance. (The story behind that is best left to be told by him.
) On my suggestion, he purchased a spare 650E engine from member "witttom", hoping that we would be able to scavenge some parts for the GL.In the course of acquiring all the excess valve clearance, a couple lobes on the intake cam were chipped on the edges. Because of that, we decided to use the cams from the E, which were perfectly pristine. The parts fiche confirms that ALL GS650s (including the X85 Turbo) use the same cams. After the requisite replacement of the base gasket, we installed the cylinders and head. After installing the E cams, I did the usual "turn the crank at least two full turns by hand". Or, at least I tried to go two full turns. I got to about 1 3/4 turns and the crank stopped NOW, with a noticeable "clunk".
We backed up, re-timed the cams and tried again. And AGAIN. For some reason, Exhaust valve #1 was being held full-open as piston #1 was coming up. Visually, the timing marks on the cam sprockets appeared to be the same, then we found the difference.
The 650E cams have 30-tooth sprockets. The 650G sprockets have 34-tooth sprockets.
Evidently the crank sprockets have 15 and 17 teeth, respectively.
I don't know how many teeth are on the 550 sprockets, but thought I would pass on this little tidbit for those that might be chasing some parts.
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