The stock porting is large, but -- it is very sharply angled.   The first step is to raise and splay the intake ports.   This is especially useful for grafting on FCR down-drafts.   The ultimate would be to install larger valves, raise both intake and exhaust ports.   The exhaust cannot go much higher without impinging on the cam oil gallery; there is ample room to go wider, though.   The intakes could be straightened and moved outward to accommodate larger carbs.   Note below how little room Yamaha gives the posrtsmith:

I experiment with 700 heads - there is no shortage of them.

Too Big on the Exhaust Too Big on the Exhaust

Heads are almost identical throughout the line. After all, the cams, rockers, and gaskets (except the head) are all the same - or close in the case of cams. I ruined a stack of 920 heads before I moved all the practice to 700s. There is very little room between the stock exhaust port and the cam "gallery." Which is really a shame: the straighter a port the better. Trying for much straightness on the exhaust is very limited. I have had a few customers who have "cored" out the intake flanges/ports and welding them in at a steeper angle. This does pick up some power, but it is a lot of work and fabrication and a frame that has been opened up. This is beyond my abilities and equipment: straightening the intakes is up to you.

Last Modified:   Mon => 02:56:19 AM PST - 09 Dec 2019 America/Los_Angeles