Justin-
Thank you again for saving those photos. I have already saved them on my hard drive and plan on putting something together with Jack's info (that is if that's ok with you, Jack). No problem,as all we have are ourselves when it comes to modifying for more performance.
I believe that you can bolt on all the 750 kits you want but if you don't get these heads flowing properly you are wasting some serious potential.The numbers have always been there,is just a matter of the getting the flow up in the lift increments without the flow diminishing.The XS head will support 100Hp but not without some serious mods
Jack-
What displacement are you shooting for? Also are you swapping to the CR con rods or just going with 256 rods and new sleeves/pistons? There looks to be some considerable weight savings with the GSXR pistons if I recall correctly.The displacement will be 707ccs (78mm bore). I'm still using the CR500 rods as they more readily available than the 256 rod. The GSXR piston,depending on dome is approximately 100 grams lighter than a stock piston,which significantly reducing the stress loads on the rod and crank as the RPMs increase. The CR rods are an overkill for street use ,just have to wind the motor tighter but I love how it changes the exhaust tone.
I have several XS motors laying around at this point in time. One is a XS1 that was seized and since then I have gotten touch with Gary Hoos. For the motor we have put together the following forma very mild build:
JE 700cc kit with no base gasket running aprox 10.5:1 compression (9.5:1 w/ base gasket)
Performance aluminum top valve spring kit
Shell #1 cam
Lectron Carbs
Intake runners
Sparx charging system (to reduce rotational mass)
Boyer or Pamco Ignition
(every part weighed and balanced on a very precise digital scale (down to 1/10 grain)
Patch, you can take this tip for what it's worth but do not under any circumstances use any type of Aluminum Valve Retainer for street use! Once the hardening coating wears off,they begin to elongate in the stem opening and eventually destroying the valves upper stem,locking the two together. I've seen this happen hundreds of time when they became popular decades ago ,when I was working part time in a friends machine shop,your decision,your money,your motor,just a suggestion.
I also plan on doing a 750 and hopefully 860-880cc motor once I get all of the research done. I'm really looking into the CR500 connecting rod swap but I'm a bit concerned if the head is going to be able to keep up. The thread in XS650 garage is great, but I need to sit down with a pencil and paper to keep all of the info straight (the math can get a little crazy) and dedicate about 2 hours to getting it all re-read and figured out.