'82 GS650 - E vs. G Head - not what you're thinking...

[Guest]

Hey all,

I have 1982 650E that I am rebuilding. Last winter I bought a replacement head and long story short, I ended up with a 1982 650 G head instead. I tried the swap and found out the mistake when the cams wouldn't fit, so I put everything back together and did what I could with what I had. I've continued to look for a proper 650E head and they have been hard to come by, so before I pull everything apart again I'm thinking about options:

1.) I know the G cams won't fit with the E motor, but for the life of me I can't remember if the E and G heads were identical? - i.e. Could I use the G head with the E cams?

2.) If I can't replace the head, how difficult is it to have two stripped cam journal holder bolt holes fixed? Currently they are helicoiled (stupid, I know....), would a proper repair be filling the holes with weld and re-tapping? or tapping the existing hole larger and enlarging the hole in the journal hole to accept a larger screw?


Thoughts?

[Guest]

The heads are the same, but as you found, the cams ARE different.

I have successfully installed an E head on a G.

[hillsy]

Am I missing something here? If the heads are the same then shouldn't either cams fit??

[Nessism]

Cam sprockets are different, eh?

[Big T]

Repairing the holes shouldn't be that difficult
You stripped out the helicoils?
Step one - buy a decent inch/pound torque wrench

[Rijko]

A helicoil for the cam cap bolts is a good solution.
Cheap to fix, if that is all that's wrong with the original head I would say go for that option.
Mixing cam caps and or cams can cause cam
stick issues, use plastigage to check for proper play.

[rphillips]

Surprised to learn, just lately, the "E" has a roller bearing crankshaft & the "G" has a plain bearing crankshaft, I realize that is the bottom end, but if that main part of the eng. is totally different, a lot more may be different also.

[Nessism]

When in doubt, look up the part numbers and compare between models. I did just that and proved that the E and G heads are the same. Camshafts are the same. Camshaft sprockets are different. The sprockets need to stay with the base engine, because the cam chain is different between the models.

[Guest]

The sprockets need to stay with the base engine, because the cam chain is different between the models.

If the chain is different, it is because one might be a couple of links shorter.

I forget which was which, but I seem to remember that one of the sprockets had 30 teeth, the other had 32. I found that because I had used the 'other' cam because the lobes looked better. While rotating the crank BY HAND for the required two full turns, the engine stopped SOLID after about 1 1/2 turns. Took the cam out, reset it, tensioned it, all that 'stuff', it locked up again. After the third time of ensuring it was installed correctly, I realized the sprocket looked a bit smaller, so I counted teeth and noticed the difference.

Typing out that last part made me realize: the G has the sprockets with more teeth than the E sprockets.

[Guest]

When in doubt, look up the part numbers and compare between models. I did just that and proved that the E and G heads are the same. Camshafts are the same. Camshaft sprockets are different. The sprockets need to stay with the base engine, because the cam chain is different between the models.

Thanks for verifying. When I compared the E and G camshaft side by side they looked to be the same size, but the E shaft was stamped R6, and the G shafts were stamped R4 near the sprockets.

Repairing the holes shouldn't be that difficult
You stripped out the helicoils?
Step one - buy a decent inch/pound torque wrench

No, I fixed a couple stripped holes with helicoils but with the amount of constant pressure and vibration applied to the cam journals I'm worried that they may fail.
I bought a decent torque wrench, but these holes were damaged trying to remove a couple stripped bolts.

If the chain is different, it is because one might be a couple of links shorter.
I forget which was which, but I seem to remember that one of the sprockets had 30 teeth, the other had 32. I found that because I had used the 'other' cam because the lobes looked better. While rotating the crank BY HAND for the required two full turns, the engine stopped SOLID after about 1 1/2 turns. Took the cam out, reset it, tensioned it, all that 'stuff', it locked up again. After the third time of ensuring it was installed correctly, I realized the sprocket looked a bit smaller, so I counted teeth and noticed the difference.

Typing out that last part made me realize: the G has the sprockets with more teeth than the E sprockets.

The "driving" (heh) factor is the G being shaft drive and the E being chain. As Ness said earlier, the sprockets match up with the bottom end.
The E cam sprockets are stamped 470 and and a smaller than the G sprockets which are stamped 342