I have a 400ex that is over bored to about 401, 10 to 1 compression piston, web cam, titanium valve springs, ct exhaust, rev box, and i was wondering if the port and polish is really going to make that big of a difference. Plus i would like to know what u guys think i should jet my carb to with these mods With the port and polish. What should i go to on the pilot. One more question is that should i get 16 front sprocket, is it going to pull it i really would like the extra top speed.

 

pilot 40. By the way, I have a similar setup but a little lower compression and the stock piston. I ported the intake and exhaust, I feel it made a big difference. One thing though, since you have a carburator, you probably do NOT want to polish the intake side. Fuel injection is usually at a much higher level of pressure so polishing helps speed up the mixture. however, with a carb at low pressure, leaving the intake rough actually helps mix the air and gas. Hope it helps.