Pretty in Pink, dunno why
Join Date: Feb 2009
Location: Redondo Beach
We have had this discussion before, interchanging heads between the 600 and the 650 going both ways.
Unfortunately, we've never had a complete resolution because the posters disappear before we find out if it worked. I think we do know that one guy salvaged a 650 head onto a 600, so the head bolt pattern should not be an issue. It should bolt up.
The common concern when talking about putting a 600 head on a 650 is the height between the bottom of the head (top of the cylinder) and the center-line of the cam bores and the squish volume of the head. The bore and stroke of the 600 was smaller and shorter, if memory serves.
If the dimension from the bottom of the head to the center-line of the cam bore to the bottom of the head is the same or within a couple millimeters then the cam timing is not a great concern. If it is off quite a bit then the cam timing culd be affected, but may be able to be accommodated well enough. If the height is shorter, there might be an issue with the valves hitting the piston.
The KLR600 piston was a pop-up design here in the States from '84 to '86, and we didn't see them after that. The 650 piston is, of course, a flat-top. What they did with the 600 in overseas markets (you're in SA, right?) is an unknown to me. With the pop-up piston the question becomes "What is the combustion chamber volume in the 600 head?". If it has a volume greater than the 650, which is about 65cc, then the compression ratio, when you put the 600 head on the 650, would drop.
That's all a very long-winded way of saying "I don't know". I will qualify my comments by saying that I've never worked ont eh a 600 top end.
Were I in your position I'd loosely assemble the 600 head to the 650 and see what the cam timing looked like, then turn it through to see if there is any interference. I'd do a visual comparison of the combustion chambers and see if there was anything really different, perhaps cc'ing the head to get an idea of the head volume. If it works, hey, it works!
Please tell us more about your situation and keep us in the loop. We'd love to know the answer! Especially, what went wrong with your 650 head? There is a shop here in the States that has good succes with line-boring the cam journals and installing babbit bearings to repair galled cam journals. It can be done.
Tom [email protected]
“Neither of the two people in the room paid any attention to the way I came in, although only one of them was dead.”
'How' are words so important they cannot be too often used.”
Sting like a butterfly.
Last edited by Tom Schmitz; 12-05-2016 at 01:41 PM.