650 head or 750 head?

i am collecting parts for a 650/750 conversion and i am looking for low end power. would it be better to stick with the 650 head or get a 750 head for the 750 cylinders? if i stay with my 650 head do i have to mod it to fit the 750 cylinders? also what cams would be good for this application? i am really looking to make a sleeper bike and suprise some guys with newer bikes!! :evil:

Post edited by: dnestell, at: 2006/03/03 21:15

ideas?sell the 79 LTD to me:whistle:

where do you live? i may be open to that?

nebraska,but ive been known to drive 2000 miles one way for bikes!:whistle:

im very intrested in this as well there are so many choices and without alot of time money and a dyno its hard to know what combination will be best.

Displacement:
650 jugs
710 kit
750 jugs
810 kit

Heads:
650
750
(as far as i can tell, the gpz heads were the same)

Cams:
650
750
750 gpz

Cam chain set up
650 with rollers (for early 650's like mine!)
750/ 650 hivo chains (apparently these only fit heads that came with them)

i think the ideal set up according to popular oppinion around here tends to be a 810 kit, 650 head with larger valves, 750 gzp cams (tach will need to be modded), and whatever can chain set up is easier (depending on what the head came with).

Is it the best set up? I dunno... i have been looking for some definative answers myself (i would like to start collecting parts).

So talk people!!

The 650 head will fit, its been done. for cams, get KZ750 cams, or GPz750 cams( if you want a sleeper go with the kz cams because the gpz ones dont have the worm gear to drive the stock tach) The 650 head has smaller combustion chambers, and that has the potential for more power, but it has smaller ports and valves than the 750 head. In my opinion, the best head would be a ported 650 head with 750 valves and the hotter cams (kz650 stock, kz750 better, gpz750 best, but no worm gear)
I'm in the slow process of building a 650/750 hybrid with an 810cc big bore kit, and I'll be using a ported 650 head with kz750 cams and valves.
One more thing, I'll be using the 650 cam sprockets on the 750 cams so I can use the roller cam chain so I can reuse all the tensioner bits. If I wanted to use the 750 cam sprockets and all of the 750 stuff, that would mean swapping cranks to change the cam chain gear that is a solid part of the crank (all one piece, you cant change the gear on the crank, you chank the whole thing) swapping cam sprockets seems a whole lot simpler/cheaper. ( I heard that the lighter roller chain will let the motor rev up a little faster too, kind of like lightening the crank, its just making the spinning mass smaller)
Scott

Post edited by: 77KZ650, at: 2006/03/03 22:25

thanks alot guys that helps. do i need to mod the 650 head to fit the 750 cylinders? will the cams and valves fit the 650 head with no mods?

Is using higher compression pistons in the 750 out of question,, as it will all fit back up and no machine work to get the larger valves or porting to get the ports larger .. port the 750 heads ?

Sell your LTD to wireman ..

thanks alot guys that helps. do i need to mod the 650 head to fit the 750 cylinders? will the cams and valves fit the 650 head with no mods?

650 head fits the 750 cylinders, the cams are all interchangeable, I think the valves are a drop in too... Mark Wing has them in his 650... maybe he will comment on that

You would probably need to get custom pistons made to achieve the same compression with using all 750 stuff vs using the 650 head on 750 jugs and using the piston kit, which would get very pricy$$$, or you could mill down the head to increase compression, but then you would need to get slotted cam sprockets and really know what you are doing to set the timing... not something I want to tackle:sick: lol.