GS850 top end on GS750? Anyone done this?

[Mastiff]

I have a 79 GS750 that needs a top end rebuild. I also have a spare 1980 GS850 engine that is in good condition. I am thinking of putting the top end from the 850 onto the 79 bottom end, since they are both 2 valve engines I did a search that said it was possible. I posted this question in the Performance forum, and was told somebody on GSR had done this. Does anybody remember who it was who did the conversion?
I am hoping to find out if there are any potential problems that have to be overcome, before I start tearing the engines apart. I don't want to take apart the 850 engine and not get the 750 running.
Thanks.

 

[odl777]

I cant rmember who did it but they had to use a dremal tool to make the casings accept the bigger jugs. I beleive you will also have to use the 850 head. Besides that i am pretty sure it is a direct bolt on.
About the head thing i know on sporters hd that you can use the 883 heads on a 1200 big bore kit and work the heads and get more power, so i wonder if you'd get more power useing the 750 head.

 

[Guest]

Yeh, I'm in the process of putting 850 jugs, head, cams & pistons on my 750 block. To my eye the cams are identical. I did have to dremel out some material where the jugs fit into the block but some careful grinding seems to have done the trick. I have run into no other problems & have heard this swap has been done many times before. You get to use the modern cv carbs that the 850 came with too.

Paul

 

[SqDancerLynn1]

I think their was mention that you needed to us the 750 cam sprockets

 

[Guest]

Cams appear identical right down to the same numbers & lettering & to my eye the same lobes.