Originally Posted by VooDooDaddy
Any idea of how much power the $1200 ported head with big valves would give vs. the stock head? Assuming you went the full-boogie with the 790 kit, stage 2 cam and so on...?
If it's only 5-8hp...? That's a lot of dough for little gain. I don't know how much hp it would end of giving over the stock head, but it had better be a bunch otherwise that's some expensive HP.....
From talking to Jeff (ProCycle), and from what I remember, the big valve head is worth at most 2-3 hp. Definitely NOT a bang for the buck item.. BUT, the DR650 motor, even in stock form, has really small valves compared to other 650s, so it's definitely a worthwhile mod. I seem to recall the dyno result of the 790, cam and head being in the 53-55 hp range.