Quote:
Originally Posted by Bill Hilly
I have went the cheaper way, and did not buy from Motocult, but I have the long duration cam, timing advance key, and a home ported head, along with a 250cc jug, and piston (70mm). I also have the roller followers, and my definitely has more power at higher RPM than it did. I don't think 10,000 rpm would be possible, and if it were, it's power would have probably dropped off, but my bike will pull, and still be making good powered past 8,000. I don't like to run it past 8,000, but I have let it get a little past it a few times, in the lower gears , mainly by accident. Some say that it's not really stressing these motors to run such high RPM , but I don't like to. Warming up the CG motor has kinda fallen out of favor, because a lot are just switching to the OHC, 6 speed, but if I compare my Hawk to my KPX, there is no real difference in range if the bikes, and I am sure the Hawk will out accelerate the KPX, and both bikes run , and run unstressed , on the fast main roads. The only use my Hawk could possibly have for a 6th gear, would be in the case of wanting it to be able to crawl through harsh rocky terrain, and therefore using lower sprocket ratios.
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I'm right there with you. A six-speed would be nice, and I'd drop in a 6-speed mainshaft, countershaft, and shift drum if a set that fits was available, but I don't absolutely need a six-speed. If I had one, I'd also take advantage of being able to run lower final gearing to have a creeper-low 1st gear.
I don't have a ported head because I'm not convinced there would be all that much to gain from it unless it was combined with a higher lift cam. Even then, the kind of higher RPM power that would potentially help isn't what I'm after.
Simply going to a bigger bore will to some extent improve the flow of even a stock head by unshrouding the edges of the valves closest to the cylinder wall. Additionally, after having gone through several of the posts here on head porting and seeing what the stock ports look like in other engines, I'm convinced that the stock ports in a CSC Zongshen head are noticeably better to begin with. I've also noticed a few other subtle differences in the CSC head. They include what appear to be iron inserts cast into the aluminum head for the threads that the rocker arm assembly bolts screw into. I don't have a different head to compare side by side, but I'm absolutely certain there are differences in the head on a CSC bike to those that I've seen posted up here from other brands.
If and when I have occasion to disassemble the head I'd certainly clean up any machining edges and put a thin back-cut above the sealing area on the valves, but I doubt that would yield any seat-of-pants difference in the way it runs with the current cam that I have.