The Official Head Thread.

[Megadan]

Since I have seen an increasing number of questions and discussions popping up about cylinder head porting for the OHV CG engines popping up, I figured now is a good time to try and centralize and focus the discussion.

There has been a few members, including myself, that has gone down this path thus far, and we all sing the praises of it.

Silva did a good basic clean up and mild reshaping of his head with a moderate deck shave. http://www.chinariders.net/showthread.php?t=20362

JerryHawk250 with his head porting thread. http://www.chinariders.net/showthread.php?t=20410

My own thread from when I first started, which unfortunately I never really finished/followed up with to this point, but has some good pictures in it here or there to show the ports and chamber. http://www.chinariders.net/showthrea...t=19200&page=9

Another good thread with a lot of detail in a shorter number of pages. http://www.chinariders.net/showthread.php?t=22777

I tried to locate some threads with other pictures to compare the TT250 head in this discussion as well, but I couldn't find them. If you happen to remember what thread it was then feel free to post it up for me.

I will end this post and start the discussion by stating that, YES, it is worth doing.

No, it will not suddenly make your Hawk/Bashan/CSC a fire breathing dragon capable of going 0-60 in 3 seconds.

What it does is open up the mid range and especially the top end enough that you can feel a difference in the higher gears, allowing it to pull much more strongly between 4000 and 7000 RPM especially. I actually stepped my gearing down compared to my last bike to bring the rpm's up a little bit to take advantage of the wider power band in the top end because of this. For me this works the best since the fastest I want/need my own bike to do is cruise at 65mph without having the throttle pegged while also being able to hold that speed up a steeper hill, which it does admirably well now.

Could I aim for a higher top speed? Sure. With 17/43 sprockets I consistently hit 70 on my non ported head Hawk with my very large butt in the saddle, but it struggled to get there, and a couple of times I managed to reach 73-74mph in more or less the most perfect of conditions/ (GPS phone app for all stated speeds). With the ported head and shorter gearing it reaches those speeds with more ease, and I suspect that if I geared it back down I could easily hit 80 maxed out. I don't really want to since the Hawk is a bit too tall and light and "unsteady" feeling for me past 70, and I have no need to go that fast in the first place, so I opted for more torque at the rear wheel.

Anyway, discuss, inquire, or enjoy at your leisure.