There are decent and better 4 valve head manufacturers. I'm not sure which is the preferred maker though.
A lot of people don't use them due to price. You can have your 2 valve head ported for much less.
Tom at Syc Powersports (sponsor here) really likes the 4 valve. Pretty sure he also has his ported too.
They should move a lot of air without needing a really high lift cam. Therefore valve float wouldn't be as much of a concern at higher RPM like the 2 valve. Valve float has been a problem for me a couple times until I bought a nice set of American made springs from Tom. (If you don't know what valve float is, the valve springs are too weak to fully close the valve at high RPM. And with the valve not fully seated, the piston makes contact and normally bends or breaks it causing engine damage)
The only reason i have not done the 4 valve is due to cost. For the price of the head, I can get a sled or ATV engine and do a conversion with a lot more HP than the 150 could ever produce. That's just my opinion though.
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My Yerban assault vehicle: 2.2mm stroker crank, 62mm Nikasil cyl, Taida large vavle head, American made valve springs, ported intake manifold, TM 28mm carb, stock CDI, Bando coil, TK exhaust, stock CVT except for the 14g sliders, 13/40 internal gears, 16T drive, 31T axle sprocket, 22" rear tires, and ONE BIG POTATO CANNON mounted on top..........
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