i'm sure you have been over this befor but i am in the process of finishing my new set up, and was wondering , the pro's and con's , of larger valves, and mainly if anyone had a rough idea at what hp and rpm they need inlarged, mainly i don't wan't to go +1 and regret not going larger. , my motor wont be run over 8900
and i'm set up for a broad power band , so i don't want to lose bottom, my head is also ported. any one have any thought's.

 

Your 720 looks like a 63-68 hp machine.
Peak hp at 7500-7700rpm.
+1 valves will be fine for this settup.
Amount of porting, size of motor, valve size and rpm range always need to be in balance.
Bigger valves in your combination will act like a too big a cam. Problem with too big vaves, is that what you loose at bottom/mid, may not be made up at top.
Velocity has to be in balance for the broadest power curve.
Pump gas with your 11.5 compression has a limit. Going to bigger valves and bigger cams without raising the compression will only make your power band narrower.

OMR

 

thank's , that answer makes my wallet very happy . i got a good deal on the piston. origonaly i wanted the 12.5.1 and wanted to do the squinch and dress up the chamber a bit , i know this does nothing mixed with high octane, and high rpm,
but has always helped off idle on all my 2 strokes , seem's to help low octaine, low rpm power, i have heard it doesn't help the ds's . but i noticed the team pammi
site listed it as a mod they do, so there must be something to it . been trying everything since the gas prices went up i can't find race gas anywhere unless i order it from the dist, i can't afford that. so it's 93 for me. just curious on what your thought's are on roughing up the intake track , to promote atomization, do jou think this would help with pump gas? i used to do it to small block chevy heads, seemed to make more torq .

 

Blend and clean up the intakes. Yes, keep them rough. Aluminum heads do not rough up like metal, so be careful.
Exhaust - blend and clean up. Here you will notice that the ports can be straightened out. Do alittle hogging here. Taper larger to the rear and stay about a 1/32 smaller than the exhaust gasket for size. Also if running the stock header, open the inside diameter of the first 1 1/2 of pipe. You will see what I mean when to look into the header pipe.

OMR

 

i have the new wileyco exhaust , there a little rough when you get e'm , but for me , tinkering is most of the fun. thank's again