Originally Posted by creeper
The way I look at it, for a factory to do this kind of hand work, there has to be justification... major justification. I would love to know the difference in CFM numbers before and after.
Somebody at KTM did this to a head, tossed it on a flow bench and said "holy crap!"... showed it to someone up the food chain who said "holy crap!"... and so it went until someone at the top said "thats going into production"... all in German of course.
Relatively small companies like KTM are good for this kind of "experimental today - production tomorrow" stuff. Fewer "suits", bean counters and red tape in the way of progress.
A "bowl job" is not very time consuming. Not that it gets done much in a production environment, but Moto Guzzi was doing it 30+ years ago on the V7 Sport heads. Not the trick Telaio Rosso stuff, all of them.
It helps, but the real money is in the seats (want to find flow obstruction? Look for the highest velocity areas. Want better flow? Make the high velocity areas work better). What the bowl job does is make the heads consistent
from one to the next. And if you are trying to extract performance, you need all the heads to flow the same +/- fuck-all. With precision seat/valves, and a quick and dirty bowl job, KTM has made a very consistent platform for tuners.
Best bang for the buck in head work? Really good valves and seats, a moderate bowl job, and drop the squish clearances to .035" +.005/-.000. But it is nice to see KTM cares. Now if they would quit putting 2-stroke bottom ends on their 4-stroke singles..........Cheers.